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Scientific Reports volume 15, Article number: 26428 (2025) Cite this article
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Cadmium Telluride (CdTe) solar cells have been successful and promising in producing solar energy at commercial scales and power plants. That is mainly due to the versatility in manufacturing of efficiency and cost-effective modules recently. The major widely utilised material for solar PV cell manufacture represents CdTe because of its excellent light-absorbing capacity and ideal energy band gap. Though the technology of CdTe PV has benefits, the limited supply of Te proves to be an issue currently. The thickness of CdTe can be reduced without affecting the efficiency significantly. CdTe photovoltaic solar cells with single and double absorber layers of ultrathin layers have enhanced efficiencies and reduced costs. It is necessary to improve how these solar cells absorb light. Making the layer narrower can help to cut down on the amount of material required, as well as costs related to fabrication. Using thin layers of material can reduce the cost and amount of material needed for fabrication. To ascertain the feasibility of suggested solar designs and forecast how material characteristics will impact their overall effectiveness, thin film solar cell architectures can be modelled utilizing computer simulations. The efficacy as well as parameter effectiveness of ultrathin CdTe Photovoltaic (PV) cells were simulated in SCAPS-1D simulation software as a function of acceptor concentration and the thickness of the light absorption layer. A double absorber layer with NiO as the windowed layer as well as FeSi₂ as the secondary layer was investigated in order to enhance the PV system’s device features as well as parameters.
The urgent global need for clean and renewable energy has driven extensive research into photovoltaic (PV) technologies as alternatives to fossil fuels, which are major contributors to greenhouse gas emissions¹. Among the available options, silicon-based solar cells dominate the market due to their efficiency, but alternative materials are being explored for cost-effective and scalable solar energy solutions². Cadmium Telluride (CdTe) thin-film solar cells have gained considerable attention for their high absorption coefficient, near-optimal direct bandgap (~ 1.45 eV), and manufacturing flexibility³.
CdTe solar cells offer advantages such as lower material usage and compatibility with inexpensive deposition techniques, making them suitable for large-scale, sustainable applications⁴. However, the limited availability and rising cost of tellurium (Te) present challenges for widespread deployment⁵. This motivates the exploration of ultrathin CdTe configurations and alternative device architectures to improve material efficiency while maintaining or enhancing performance.
Based on thin film technology, which comprises several thin film deposition processes involving sputtering and molecular beam epitaxy, the scientific community has recently expressed a great lot of interest in solar cells. Thin film solar cells composed of copper indium gallium sulphide (CIGS) or CdTe, which have an efficiency of above 20%, offer appealing alternatives to DSSCs because of their low efficacy and short lifetime. The unique features of the thin CdTe layer make it widely used. CdTe-oriented thin-film PV cells are becoming more and more familiar for a variety of applications because of their excellent light absorption ability, abundance, exceptional effectiveness, long-lasting performance, and affordability. Furthermore, the material is widely utilised in many other methodologies, including nanoscale devices, sensors, and solar panels. PV heterojunctions are made using binary compounds like cadmium sulphide, CdTe, and materials from groups III and IV⁴. The growth as well as debate of CdTe-based PV cell technologies have received particular interest⁵. CdTe methodology represents the major economical option; it is over 50% less expensive than CIS as well as Si frameworks. Its chemical stability, extended lifespan, and excellent band energy gap of about 1.6 eV make it perfect for attaining optimal device effectiveness in every aspect as a mono junction device on the basis of the Schockley-Queisser limit⁶.
The ability of CdTe to help both P as well as N conductivity represents one among its advantages. Despite extensive research on CdTe (from 1900 to 1890), its use as a material for quantum dots as well as polycrystalline thin films is very new (within the last ten years). The survey reports improvements in CdTe’s effectiveness as well as stability. A potential absorber in the development of a P-type semiconductor for application in thin-film solar technology represents CdTe. The need for more economical as well as ecologically friendly energy sources in the future is what is driving the current trend towards PV conversion. Cost-efficient semiconductors as well as substrates are used in thin-film devices to minimise material consumption, often at the expense of effectiveness. This approach presents chances to reduce costs and improve conversion efficiency. This topic has been studied by several academics, resulting in a wide range of PCE values from 12.02 to 44. Economical thin-film methodology has been developed using a range of materials. For solar energy devices, researchers have been focused on developing light weight, flexible as well as affordable semiconductor materials⁷. For Thin Film Solar Cells (TFSCs) therefore highly efficient, non-toxic, and relatively cheap p type absorber layer material are employed. This field of research has the main objectives of reducing dependency on dangerous chemicals and reducing the cost of solar cells⁸. Different ways of using different kinds of semiconductor materials are used to meet these objectives. PV cells can be designed, and assessed using SCAPS software, which can be considered to be the major, popular and effective platform⁹.
The drift-diffusion approach is used to analytically handle the continuity equations for both electrons and holes in 1D. Additionally, SCAPS-1D is frequently employed by researchers as well as engineers to study the device effectiveness associated with different cell kinds and to simulate as well as evaluate the properties linked to solar cells in different settings. Due to its high efficacy and cost, the TFSC program has attracted a lot of interest. Collectively, the layers that comprise the solar cell’s structure convert sunlight into electrical energy. The method offers the lowest manufacturing costs when compared to other solar techniques, which makes it appealing for broader use¹⁰. According to researchers, the proposed model would improve effectiveness and successfully rival current solar cell technology. As a cost-effective and efficient method for generating renewable energy, CdTe TFSCs have demonstrated great potential¹¹. Solar cells aim to achieve two goals: higher effectiveness as well as more competition from various PV methodologies.
More than 99% of solar photons across a wide range of wavelengths may be absorbed by CdTe, a P-type semiconductor having a straight band gap as well as a high absorption coefficient. N type cadmium sulphide (CdS) generates an energy gap of 2.43 eV by forming a robust heterostructure with CdTe, suggesting a wide range. It was used as the buffer layer in CdTe cells because of this property¹². The way the energy gap interacts with the absorber as well as buffer layers has a big impact on their effectiveness. A buffer layer with a high work function for back contact as well as low resistance is required to save energy. To enhance the functionality of CdTe-oriented cells, several researchers have investigated different types of back contacts¹³. An earlier known nickel (Ni) work function of 5.5 eV was employed to facilitate effective majority carrier insertion¹⁴. Achieving the minimal energy needed to liberate the valence electron from a Ni material is crucial for comprehending surface interactions and electron emission in solar cell methodology. The different back-contact materials affecting solar cell effectiveness was also investigated in order to increase PV efficacy¹⁵.
In this configuration, CdTe and other components are mixed with the ecologically favourable compound FeSi2. The absorber layer FeSi₂ exhibits an absorption coefficient (α) larger than 10⁵ cm⁻¹ and an energy gap (Eg) of 0.87 eV at an energy of 1 eV. The two primary components of FeSi₂, iron (Fe) and silicon (Si), make up the majority of the Earth’s crust. Consequently, it has returned as a potentially inexpensive part of solar cell absorber materials. Photogenerated electrons can pass via the front of the cell and link to an external load thanks to transparent electrodes¹⁶. The intended study is to develop, design, and assess a solar cell (Al/FeSi₂/CdTe/NiO/Ni) in order to forecast the impacts of different circumstances on semiconductor carrier movement as specified by core equations.
Since it tackles important issues in the realm of solar framework, this paper is noteworthy. The primary goal related to the endeavour is to create effective and reasonably priced ultrathin CdTe solar cells. CdTe has become a major material for solar energy uses because of its remarkable optoelectronic qualities, perfect bandgap, as well as high absorption efficacy. Nevertheless, the cost and presence of Te severely limit the scalability associated with the CdTe-based applications. This work presents a novel technique that demonstrates how reducing the CdTe layer’s thickness improves effectiveness while using less material. This study utilizes SCAPS-1D design to explore new configurations that incorporate a double absorber layer with FeSi₂ as a secondary absorber and NiO as a window layer in order to increase device efficacy. This creative strategy not only improves the efficiency of power conversion but also adeptly manages the economic as well as ecological concerns related to Te use. The suggested concept is closely related to research initiatives aimed at creating sustainable thin-film solar cell methodology. By improving the effectiveness as well as feasibility of vast-scale CdTe solar panels, the research also provides new insights. This will connect the gap between material constraints as well as the rising necessity for renewable energy sources worldwide.
The paper contribution is as below.
To decrease the width of the layer for reducing the material quantity as well as the cost for fabrication.
To assist in producing a CdTe solar cell module on a big scale because Te is not a readily available element.
To ascertain if anticipated solar structures are feasible and to predict how material qualities would affect the device’s entire effectiveness.
To forecast and examine the variables that affect the development of ultrathin CdTe PV cells, like the majority carrier concentration as well as the thickness related to the light absorption layer.
To investigate a double absorber layer that improves the PV system’s parameters as well as device properties using NiO as the windowed layer as well as FeSi₂ as the secondary absorber.
The structure of the paper is as follows. Ultrathin CdTe photovoltaic solar cells with single as well as double absorber layers are introduced in Sect. 1. The literature review is in Sect. 2. The suggested framework including materials as well as techniques is presented in Sect. 3. Results and discussion are in Sect. 4. The conclusion is in Sect. 5.
The development of advanced PV methodologies has been fuelled by the growing demand for energy worldwide as well as the urgent requirement to switch to sustainable energy sources. CdTe solar cells’ exceptional efficacy, affordability, as well as simple production process have drawn a lot of interest. Yet, the need for comparatively thick absorber layers in typical CdTe solar cells drives up production costs and resource usage. This encourages the development of ultrathin CdTe PV solar cells, which seek to employ less material without compromising or maybe improving device performance. Ultrathin CdTe cells having single or double absorber layers have special chances to enhance carrier collection as well as light absorption. Using dual absorber layers to absorb various energy levels, the device may make greater use of the sun’s spectrum. This approach boosts the overall effectiveness of the device and opens up possibilities for innovative bandgap engineering. Decreasing the thickness associated with the CdTe layers also enhances charge carrier mobility and lowers recombination losses, both of which are essential for achieving greater power conversion efficiency. The use of CdTe cells in mobile devices, wearable technologies, as well as building-combined PV methodologies is also increased by ultrathin designs, which enhance flexibility as well as lightweight characteristics. The difficulties—like ensuring effective light absorption in fewer layers as well as resolving material stability—intensify research into new methods as well as production methods. The global dedication to creating cost-effective, environmentally friendly, and efficient renewable energy sources is demonstrated by the development of ultrathin CdTe solar panels.
The survey for earlier published works pertaining to the current topic is covered in this part, along with the limits as well as approaches that were taken into consideration.
This work proposed a unique alternative method that employed FeSi₂ as the secondary absorber layer as well as In₂S₃ as the window layer to enhance solar efficacy features^27,28,29. Utilizing SCAPS-1D simulation, the proposed double-absorber (Cu/FTO/In2S3/CdTe/FeSi2/Ni) methodology was thoroughly examined as well as analyzed. Comprehensive simulations pertaining to the window layer thickness, absorber layer thickness, acceptor density (NA), donor density (ND), defect density (Nt), series resistance (RS), and shunt resistance (Rsh) were conducted in order to maximise the aforementioned configuration as well as increase PV efficacy. According to this research, 0.5 μm was the optimal thickness for both the CdTe as well as FeSi2 absorber layers in order to maximise efficiency (η). In this instance, the optimal window layer thickness was 50 nm. The recommended technique also worked well at 300 K as an operating temperature. By increasing the absorption related to the solar spectrum at longer wavelengths (λ), the FeSi2 layer’s integration into the cell format has resulted in a noticeable enhancement in quantum efficacy. The research’s findings provided a practical approach to producing high-performing as well as reasonably priced CdTe-based solar cells.
This study thoroughly developed and examined R2R-compatible alterations in the production of ultrathin, sintered CdTe NC solar cells³⁰. These involved (1) using scalable deposition methods including spray coating as well as doctor-blading, (2) perfectly applying a sintering chemical to sinter CdTe NCs without a bath, and (3) radiative heating using an infrared laser. Prior to being compared with the conventional, non-R2R-friendly method, which included heating the NCs on a hot plate, spin-coating them, and immersing them in a CdC_l2 solution, the effects of each modification on the CdTe nanostructure as well as solar cell efficacy were examined independently. These advancements made it easier to produce ultra-low-cost, solution-processed solar panels in large quantities on flexible or curved surfaces.
For this investigation, ultrathin CdTe solar cells were developed with absorber thicknesses ranging from 50 to 200 nm³¹. It was discovered that the open-circuit voltage (VOC) as well as short-circuit current (JSC) both dramatically dropped as the thickness of the absorber layer minimized. Inadequate light absorption was the main cause of the JSC’s deterioration. Additionally, covered in this study were the factors that led to the reduction in VOC. The analysis of dark current voltage features confirmed that the ohmic shunting current contribution to total leakage current was increased with decreasing thickness of CdTe absorber layer. In addition, the ultrathin CdTe solar cell characteristics were examined under different light exposure levels and temperatures. It provided a basis for the development of ultrathin CdTe solar cells in the future. The researchers studied MgCl₂ as a cheaper and safer chlorine containing alternative to thermally treating CdTe³². Thermally treated CdTe films of MgCl₂ were found to have better crystallinity, surface morphology, impurity profile, and carrier density than did those treated with CdCl₂. Amongst the samples that were subjected to 0.4 M MgCl₂, the optimal results were obtained with a band gap around 1.46 eV, refractive index of 2.84, carrier concentration of 9.81E + 15 cm − 3, mobility of 35.08 cm2/V-S, and low resistivity. The findings indicate that MgCl₂ may replace the current CdCl₂ in the manufacturing procedure, minimizing the environmental hazards and lowering the cost to produce CdTe oriented solar cells. A preliminary simulation was carried out in this work to link to a general FTO-SnO₂-CdS-CdTe combination to confirm the accuracy of the simulation technique³³. Lowering the cost of the device was investigated by using an extremely thin absorber layer. The rear contact was made with a thin layer of A-type copper oxide as Hole Transport–Electron Blocking Layer (HT–EBL). In addition, monolayer CdS: Zn and bilayer ZnS–CdS combinations were used for the electron transport layer. Next, the suggested simulated cell parameters were modified in order to increase efficacy. SCAPS-1D simulation software was used to demonstrate it to model a solar cell with CdTe and cadmium sulphide (CdS)³.
A solar cell has the structure consisting of CdS, Zinc Oxide (ZnO), Nickel oxide (NiO), CdTe, as well as Au layers. The Hole Transport Layer (HTL) was made of NiO, and the Transparent Conductive Oxide (TCO) layer was made of ZnO. The absorbance coefficients related to ZnO, CdS, and CdTe were systematically assessed following their synthesis by a simple chemical procedure. The experiment’s absorption coefficient information was further analyzed in SCAPS-1D to determine the influence of these materials on solar cell efficacy. It also looked into the effect of carrier concentration, CdTe thickness, and defect density at the CdS/CdTe interface on the properties of the solar cell. The optimized solar cell, which achieved efficiency of 28%, was the basis for great promise for efficient and inexpensive solar energy harvesting^24,25,26.
Table 1 lists the characteristics as well as limitations of a few of the current approaches.
Although extensive research has demonstrated the potential of CdTe-based photovoltaic cells for achieving high efficiency and operational stability, several critical issues remain unaddressed—particularly in the context of material sustainability and advanced ultrathin configurations. One prominent challenge is the dependency on tellurium (Te), a scarce and expensive element, which restricts the scalability of CdTe technologies. Despite the well-established benefits of CdTe as a primary absorber, existing studies have not adequately addressed strategies for reducing Te usage while preserving or enhancing device performance.
Moreover, most prior works have concentrated on single absorber architectures, overlooking the promising enhancements offered by dual absorber layer configurations. The synergistic interaction between CdTe and alternative absorbers such as FeSi₂—known for its infrared photon absorption and earth-abundant composition—has not been sufficiently explored. There is also limited investigation into how such multilayer structures impact carrier transport dynamics, recombination behavior, and energy conversion efficiency in ultrathin solar cells.
Given these gaps, the present study aims to systematically investigate a novel thin-film solar cell structure using SCAPS-1D simulation, incorporating CdTe and FeSi₂ as dual absorber layers, complemented by NiO and In₂S₃ as window and buffer layers, respectively. The objective is to evaluate how such a configuration can improve photovoltaic performance while minimizing Te dependency, thereby contributing to both technological advancement and material sustainability in next-generation PV devices.
This section describes the material configurations as well as the simulation technique used to study the effectiveness of ultrathin CdTe PV cells. The device structure is developed by the SCAPS-1D simulation tool-SCAPS (Solar Cell Capacitance Simulator)−1D version 3.3.10, and the PV performance is predicted in the introduced project. CdTe is the main absorber, FeSi2 is the secondary absorber, and NiO is the window absorber in proposed cell model. Sustainability as well as effectiveness were the bases on which each material was selected for its special qualities. The device setup is made so that realistic boundary constraints, material properties, and optical parameters can be ensured to yield accurate results. The device efficacy is increased through systematic alteration of significant factors including layer thickness, doping concentrations, and defect densities. Characteristics such as short circuit current density, fill factor, (:{V}_{OC}) and power conversion efficacy are analyzed using recombination processes as well as carrier movement equations in the simulation. The method offers a general picture of the material properties, the device design, and the way that they relate to the overall effectiveness of the ultrathin CdTe solar cells.
This section deals with the components used to fabricate the ultrathin CdTe PV framework. The main absorber layer of the suggested concept is CdTe which has ideal bandgap energy. CdTe’s ability to absorb light so well makes it a good candidate for conversion of solar energy. The optimal direct bandgap for CdTe is around 1.45 eV, near the optimal value for maximum solar energy conversion efficiency under typical illumination circumstances. CdTe has a high absorption coefficient and can therefore absorb more than 99% of the incoming sunlight on a very thin covering which is often only some micrometres deep. For this reason, it performs quite well for ultrathin solar cell types and also brings the benefit of material savings without sacrificing performance. In addition to the optical properties, CdTe has improved stability under a variety of environmental conditions. Such guarantees make sure that the solar cells are dependable and long lasting. It also promotes p type conductivity, which is essential in this case for the construction of effective p-n junctions, with p type materials such as CdS. CdTe is economical and scalable in production processes since it works better with thin film deposition approaches such as sputtering and vapor deposition. The combination of these characteristics facilitates CdTe’s ability to achieve very high efficacy in commercial solar modules and makes it the dominant absorbing material for the suggested device concept. The special benefits of CdTe are leveraged to increase device effectiveness in the created endeavor.
Iron silicide (FeSi₂) is included in order to improve the device’s efficiency and to give another absorber layer. For the secondary absorber, FeSi2 is chosen for specific problems that exist in CdTe solar cells. The bandgap energy of FeSi₂ of 0.87 eV means that it may efficiently absorb photons in the longer wavelength range that are not absorbed by the primary CdTe layer. The total photocurrent generation has increased as well as the spectrum responsivity of the device improved, due to this feature. The reason is that FeSi₂ contains silicon as well as iron, two common, non-toxic, and affordable elements. FeSi₂’s amazing thermal stability, which ensures long term dependability under operational conditions, determines the lifespan of solar cells.
Large bandgap, good transparency in the visible, and compatibility with NiO due to its wide bandgap are characteristics of the window layer which contains NiO. This will allow maximum light penetration, also reducing recombination losses at the front contact. The bandgap of 3.6–4.0 eV is reduced to optical losses as well as preventing recombination at the front contact, by creating an appropriate band alignment with CdTe. Because NiO is completely mobile, it can be stable under harsh environmental conditions and extract charge efficiently. This helps prolong the device’s useful life and effectiveness. NiO is a superior material for PV applications due to its improved hole transport and chemical as well as thermal stability under operating conditions. The reason for selecting these materials was their affordability along with their optical and electrical properties as well as sustainability. It is consistent with the aim of establishing solar cell technology in a scalable as well as efficient manner.
The present work utilized version 3.3.10 of SCAPS-1D, a numerical modelling programme developed at Gent University, Belgium designed for simulating thin-film heterojunction solar cells. The software’s description and operational principles are detailed in the literature^14,15,16. SCAPS-1D (version 3.3.10), developed by the University of Gent, Belgium, was used to simulate the behavior of the proposed ultrathin CdTe-based photovoltaic structures. The software numerically solves the coupled semiconductor equations—namely Poisson’s equation and carrier continuity equations—under steady-state conditions. It accounts for recombination, carrier transport, doping-dependent mobilities, and defect states across heterojunction interfaces. All device layers were defined with realistic material parameters and optical constants based on published literature^{14,15,16,17,18,19}.
The published study^{17,18,19,20,21,21} tests the validity associated with the SCAPS-1D simulation program since the findings related to the simulation as well as experiments agree well. As a result, solar cells dependent on CdTe may be effectively modelled and analysed using SCAPS-1D software. The simulation setup is carefully designed to model and analyze the performance of ultrathin CdTe photovoltaic cells under realistic conditions. The simulation begins by defining the device structure incorporating layers such as CdTe, FeSi₂ and NiO. CdTe is used as the primary absorber, FeSi2 is used as the secondary absorber in the double-layer configuration and NiO is used as the window layer. Boundary conditions are specified to represent the electrodes behaviour. It is assumed that both front and back interfaces have ideal ohmic contacts for efficient carrier collection. In Table 2, the material properties: bandgap energy, mobility, electron affinity, and doping concentrations are chosen, and they are presented. Thickness of CdTe layer is changed to assess its effect on device efficacy. The effect of FeSi₂ to the absorber stack is maximized by optimizing the thickness and carrier concentration of FeSi₂. Furthermore, the proposed method also makes some presumptions including isotropic carrier movement and homogeneous doping in each layer. The proper change in the settings for interface defect density and surface recombination velocity is made to represent realistic material interfaces. Examples of optical characteristics that are used to precisely calculate photocurrent generation include absorption coefficients as well as reflection losses. The effects of operational characteristics such as light intensity and temperature are also simulated to gain a full understanding of the cell efficacy. This comprehensive SCAPS-1D system allows one to make the exact forecast of PV properties under different material and structural configurations.
Figure 1(a) shows the configuration of the apparatus used in the developed apparatus for this simulated research study, while Fig. 1(b) shows wide energy gap (E_g) and thickness of every layer in a component as indicated by the data of energy band obtained from the simulation experiment.
A structural outline of the suggested device is given in Fig. 1(a) that includes layer arrangement and function of each component in the solar cell. The developed multilayer structure is designed to be loss free so as to optimally produce charge, provide means for the creation of the charge, and capture of light. Optimising the absorption of incoming light from visible to infrared, the layers are set up to do so. Once the light reaches the surface of the device it enters the active layers, and the photons reach the front contact. A secondary absorber, the uppermost layer, FeSi₂, is also very good at absorbing photons from the infrared part of the solar spectrum. This also improves CdTe, the main absorber, with a band gap of 1.5 eV and intended to absorb visible light. Additional photogenerated carriers are introduced by the FeSi₂ layer which raises the current output of the device as a whole. It also ensures efficient charge transfer to the lower CdTe layer through its band alignment and enables smooth carrier transport between the two absorbers.
Charged generation and light absorption is dependent upon the CdTe layer, which is the main part of the device and p type. The CdTe layer was put under FeSi₂ due to its perfect bandgap and perfect absorption of visible spectrum photons as well as generation of electron hole pairs. The dual absorber FeSi₂ and CdTe combination may give the device the ability to capture a wider spectrum from the solar radiation. Consequently, the power conversion effectiveness of the gadget will improve. A hole transport layer of NiO is placed beneath the CdTe layer. As a result of its wide band gap of 3.6–4.0 eV, light absorption is unhindered in NiO. It collects and transports holes formed in the layers of CdTe and FeSi₂ effectively. The back contact is utilized as a recombination barrier to lower carrier losses at the interface and serves to increase the (:{V}_{OC}) by acting as a recombination barrier. The last layer is the nickel (Ni) substrate/back contact. This layer supplies a good mechanical base for the entire construction and a reliable electrical way for the carriers to complete the circuit. Effective elimination of photogenerated holes from the NiO layer is enabled by Ni. Overall, it improves the effectiveness of the gadget and decreases resistance losses. Optical and electrical losses at each interface are to be reduced by the recommended arrangement. Using two absorbers’ spreads photogeneration across two layers, reducing recombination losses. Efficient carrier movement is ensured by the configuration of the CdTe, FeSi₂, and NiO layers. Maximum light entry into the active layers is made possible by the frontal contact at the top, which reduces shadowing. This configuration achieves a better balance among efficient carrier extraction and ideal light absorption. While the NiO and Ni back contact work together to effectively convey carriers, the combination of CdTe and FeSi₂ as absorbers allows the device to use both the visible as well as infrared portions of sunlight.
The band bending at the CdTe and FeSi2 junction, as well as the various doping doses used in this investigation, are clearly seen in Fig. 1(b). The picture also indicates that the bandgap related to the FeSi₂ layer is around 0.87 eV. It can absorb infrared photons thanks to its narrow bandgap, which enhances CdTe’s absorption characteristics. The valence as well as conduction band edges of FeSi₂ are well located to carry the photogenerated electrons as well as holes to the next CdTe layer. It shows that the way of collecting and transporting charge between layers is working fine. In contrast, CdTe, the main absorber material, absorbs well visible light due to its bandgap of 1.5 eV. The conduction band edge of it aligns with that of FeSi₂. Since the electrons are transferred from FeSi₂ to CdTe in a smooth manner, this guarantees a smooth transition of electrons from FeSi₂ to CdTe. Hole migration and separation at the heterojunction are superior due to the slight misalignment in the valence band edge of CdTe relative to that of FeSi2. As a result, recombination losses are reduced, and efficient charge separation is assured.
The buffer layer is the In2S3 layer, which has a broader bandgap of around 2.82 eV. Its position in the energy band diagram indicates that it acts as a protective layer. This reduces the recombination at the CdTe interface and enhancing carrier mobility. Also, the high energy bandgap ensures that it remains transparent to most of the incident light and allows maximum light penetration to the underlying absorber layers. The Fluorine-doped tin oxide (FTO) has a wider bandgap of approximately 3.6 eV which ensures that has a highly transparent conducting oxide. Due to this, it allows incident light to reach the active layers without significant optical loss. Its conduction band alignment supports efficient electron extraction. The separation between the quasi-Fermi levels for electrons (:Fn) as well as holes (:Fp) across the absorber layers illustrates the device photogenerated voltage. The larger the separation, the higher the (:Voc) attainable in the solar cell. The quasi-Fermi levels remain constant across each material which indicates the minimum energy losses and efficient carrier collection throughout the structure.
(a) Structure of the developed device, (b) Energy diagram.
This research focuses on a PV cell structure consisting of layers of Al, FeSi₂, CdTe, NiO, and Ni. The CdTe layer acts as a P-type absorber possessing higher energy gap (Eg) of 1.55 eV, while the FeSi₂ layer acts as another absorber with a lower Eg of 0.875 eV. These two layers form a junction. The window layer, NiO, has an Eg of 2.82 eV. The proposed structure, which combines a double absorber made of CdTe and FeSi₂, is introduced with the aim of improving performance. The Ni back contact as well as an additional FeSi2 layer are positioned among the CdTe layer. Ultimately, conventional SnO2 material has a bandgap energy ((:{E}_{g})) of 3.6 eV. This material is typically used as an open region and functions as an FTO layer. This proposed PV cell structure has several key components. It includes a 0.50 μm absorber made of CdTe of P-type, with a doping concentration of N_A = 1 × 10¹⁰ cm-3. In addition, there is a 0.50 μm p+-type absorber made of FeSi₂, of higher doping concentration of N_A = 1 × 10¹⁷ cm⁻³. The back metal contact of the cell consists of a layer of Ni. On the front side, there exists a 0.06 μm n-type NiO window layer, followed by a 0.04 μm layer of FTO (SnO₂). Nickel (Ni) having a work function of 5.20 eV is used to construct the metal layer, while aluminium (Al) having a work function of 4.5 eV makes up the top contact. Figure 2. 1D SCAPS Simulation tool.
The thickness of the CdTe absorber layer was systematically varied in simulation to identify an optimal balance between photon absorption, carrier collection, and recombination losses. As expected, increasing the CdTe thickness initially improved short-circuit current density (Jsc) and power conversion efficiency (PCE) due to enhanced light absorption. However, beyond approximately 2 μm, performance gains saturated as recombination began to offset additional photogeneration, consistent with established behavior in thin-film solar cells. To address this efficiency plateau while reducing material usage, a secondary absorber layer of FeSi₂ was introduced beneath a thinner (0.5 μm) CdTe layer. This dual-layer configuration enabled spectral extension into the infrared region, thereby improving photocurrent without requiring a thick CdTe layer. Hence, in the proposed model, a total absorber thickness of 1.0 μm (0.5 μm CdTe + 0.5 μm FeSi₂) was selected as optimal for high efficiency and low material consumption. The performance evaluation related to the ultrathin CdTe PV solar panels is depicted in this diagram. Subplot (a) displays the current density-voltage (J-V) characteristics for different absorber layer thicknesses, demonstrating that efficacy rises with layer thickness. Subplot (b) displays the Quantum Efficiency (QE) as a function of wavelength, emphasising the high response in the 500–800 nm range. Subplot (c) investigates the connection among absorber thickness as well as (:{V}_{OC}) and short-circuit current density (Jsc). Subplot (d), which displays the change in Power Conversion Efficiency (PCE) as well as Fill Factor (FF), emphasises the effect associated with layer thickness.
The first section investigated the connection among the PV cell’s distinctive features as well as the absorption layer’s width. The effect on final output device factors like Jsc, (:{V}_{OC}), FF, PCE, and QE was examined after the thickness was progressively changed from 1.00 μm to 6.00 μm. All of the remaining variables remained constant throughout the trial. The AZO, CdTe, as well as NiO layers had the highest carrier concentrations at 1015, 1017, and 1019 cm-13, correspondingly. The AZO as well as NiO layers were 10 nm wide as well as 20 nm thick, respectively.
Figures 2a as well as b display the J-V effectiveness curves as well as matching Quantum Efficiencies (QE) for different absorption area thicknesses. Figure 2a demonstrates that the device’s attributes exhibit the same pattern as the absorber layer’s width changes from 2 to 6 μm. Figure 2(b) demonstrates that, particularly in the 550–800 nm wavelength region, the QE is lowest at a thickness of 0.5 μm. The reference⁴ illustrates the reason for the decreased light transmission at thicknesses below 1.00 μm. QE increased with increasing CdTe thicknesses; thicknesses of 2.00 μm achieved a QE of 88–93% in the 530–700 nm wavelength range. It has been verified that CdTe having a thickness of 2 μm may absorb 99% of the light in that particular wavelength band.
The relationship among Jsc as well as the absorbing layer’s thickness is seen in Fig. 3d. The thickness of 0.5 μm was used to get the lowest Jsc value of 23.62 mA/cm2. Because of the insufficient thickness of CdTe, incoming light with wavelengths between 500 and 820 nm is partially absorbed, resulting in a decreased rate of electron-hole production (Fig. 2b). At a thickness of 2.00 μm, the Jsc reaches a maximum of 26.16 mA/cm2, increasing correspondingly as CdTe spreads. Because of their longer optical path, the thicker sheets exhibit better absorption⁴, increasing the probability of photon absorption.
The Jsc value stays constant between 2 and 6 μm in thickness because of a high carrier recombination rate in comparison to the generation rate. Jsc approaches a saturation threshold as CdTe thickness increases. Voc decreases by 0.017 V as CdTe thickness rises. In particular, Fig. 3c shows that when the width increases from 0.50 μm to 2.00 μm, the voltage drops from 0.77 V to 0.73 V. An increased likelihood of carrier recombination at the junction results from the widening of the absorber layer³¹. However, while the CdTe layer thickness fluctuates among 2.00 and 6.00 μm, the Voc (open-circuit voltage) remains constant. This occurs because the Jsc is constant as well as the saturation current density (J0) is unaffected by the layer’s thickness. Figure 3d shows the behaviour of FF, showing that when the thickness of CdTe grows from 0.50 to 1.00 μm, the percentage increases from 66 to 74%. The increase in cell output, which results from improved QE as CdTe thicknesses climb, is connected to this rise. However, when the CdTe layer thickness increases to 2.00 μm, the proportion decreases, reaching 73.42%. Even though the device’s operation is virtually unaltered, this decline is brought about by a rise in short circuit current. The product of voltage as well as current at short circuit has an inverse relationship with the FF. It is found that when both Jsc and Voc are constant, FF stays constant among the thickness range of 2.00–6.00 μm.
(a) Current voltage relation, (b) Efficiency, (c) Voc versus Absorber thickness (d) PCE versus Absorber thickness.
This graph compares the QE (η) spectra of ultrathin CdTe PV solar cells having single and dual absorber layers. Up to around 800 nm, the individual absorber (CdTe) shows great effectiveness; beyond that, effectiveness significantly declines. The effectiveness range is significantly expanded by the dual absorber (CdTe + FeS₂), which maintains good QE up to around 1400 nm. When compared to the single absorber layer, the dual absorber layer appears to accomplish superior overall because it increases light absorption in the infrared range.
One important aspect influencing the total effectiveness associated with the solar cells is the thickness related to the absorption layer. By contrasting the outcomes, they provide with those from experimental manufacturing, CdTe cells may be assessed. Figure 3 illustrates how the thickness associated with CdTe, which ranges from 0.10 to 4.50 μm, affects the efficiency related to the PV cell. As shown in Table 2, the data related to every layer is used at 330 K in direct sunshine. Improving the thickness related to the CdTe absorber layer enhances effectiveness (η) by increasing the quantity of light energy absorbed from solar radiation. At 0.10 μm and 4.50 μm thicknesses, correspondingly, the effectiveness (ƞ) is 6.25% and 15.45%. The connection among the thickening as well as the increase of ƞ is seen in Fig. 3. Furthermore, there was a commensurate variation in the (:{V}_{OC}) as well as JSC with respect to changes in the thickness related to the PV cells’ absorption layer. The quantity of electric charge generated by a PV cell when exposed to light of a certain wavelength is known as QE. The ability of a PV device to extract valence electrons in relation to the quantity of incoming photons is measured by the External QE, or EQE. Figure 3 shows the QE for the fundamental CdTe cell’s optimal width.
Efficiency versus Wavelength of dual CdTe and FeSi₂ layer.
This figure shows the performance measures for ultrathin CdTe solar cells having single (CdTe) as well as dual absorber layers (CdTe + FeSi₂) at different absorber thicknesses. Dual absorbers’ enhanced efficiency (η) is seen in the top subplot. While single absorbers exhibit a little decline, the second subplot highlights a constant FF for dual absorbers. When thickness increases, single absorber’s Jsc and Voc increase more dramatically, while dual absorbers consistently retain greater values.
A high defect doping level can be employed to reduce the recombination of minority charge carriers (electrons) at the metal layer associated with the back contact while thickening the absorber or including another layer. However, because of the high cost as well as wide availability of the appropriate material, increasing the thickness is not always feasible. For this specific goal, FeSi₂ (doped at 1 × 10¹⁷) is placed next to CdTe (doped at 1 × 10¹⁰) in this investigation. The interaction between FeSi2 as well as CdTe creates a potential that stops the least charge carriers from going to the rear area, much similar to a P-N junction. Consequently, the FeSi2 layer will decrease the ambient electron flow and raise the short-circuit current by reflecting the minority carriers. A second absorber layer improves the efficiency of the solar cell by decreasing the rate of surface recombination. The data listed in Table 2 is used in this experiment, which is conducted beneath solar light at 330 K. The FeSi₂ layer has a beginning range of 0.10 μm to 4.50 μm. This first investigation indicates that the cell’s diameter falls between 0.30 and 1.80 μm.
With a 0.10 μm absorber layer, the typical CdTe cell has an efficacy of about 25%. Consequently, it has been determined that a 0.5 μm thick FeSi₂ layer is suitable and will be employed in future research. When the thickness related to the newly developed CdTe PV cell is reduced by 0.5 μm, it obtains an overall effectiveness (ƞ) of 27.35%. This indicates a significant improvement in absorber layer effectiveness. This is primarily because of the solar cell’s 1 μm-thick CdTe and FeSi₂ layers serve as absorbers.
The inclusion of the FeSi₂ layer boosts the solar cell’s ability to absorb photon energy. More electron-hole pairs might be created as a result of the substantial amount of light that is absorbed. The FeSi₂ layer raises the JSC from 25.505 to 49.78 mA/cm² and the (:{V}_{OC}) from 0.631 to 0.656 V. Higher PV effectiveness results from these improvements, which significantly boost the efficacy of conventional C_dT_e-oriented PV cells. Despite this, the FF drops from 83 to 82%. The Maximum Power Point Voltage (MPPV) as well as Maximum Power Point current (MPPJ) both drop simultaneously when the (:{V}_{OC}) and JSC both increases.
The observed improvement in photovoltaic performance with the inclusion of FeSi₂ as a secondary absorber layer can be attributed to its physical and electronic properties. FeSi₂ has a narrower bandgap (~ 0.87 eV) compared to CdTe (~ 1.5 eV), enabling it to absorb longer-wavelength photons in the near-infrared region, which CdTe alone cannot harvest effectively. This spectral extension contributes directly to the increased short-circuit current density (Jsc). Additionally, the favorable conduction band alignment between FeSi₂ and CdTe facilitates efficient electron transfer while creating a built-in potential barrier that reflects minority carriers away from the back contact, thereby reducing recombination losses. This cascade-like energy band structure supports better charge separation and extraction across the device. Moreover, FeSi₂ is composed of earth-abundant and non-toxic elements, offering a sustainable alternative to conventional heavy-metal-based absorbers. Collectively, these physical advantages explain the improved quantum efficiency and power conversion efficiency observed in the dual absorber configuration.
The effect of the ideal thicknesses on QE is seen in Fig. 4. Because the resultant absorption layer absorbs more light, the PV’s QE first rises as the CdTe layer’s width rises. Only a tiny percentage of the visible light spectrum is appropriate for things to absorb photons. Thus, QE or photon absorption efficiency steadily decreases for entire materials until it reaches zero at specific wavelengths (λ). Because C_d and T_e are more readily available, larger CdTe layers cost more to provide better outcomes. The cost of producing these devices would go down if the thickness associated with the CdTe material were reduced since less Cd and Te would be required.
Impact of changing NiO window layer thickness.
The results show that compared to the present method, the proposed low-cost solar cell model exhibits better efficiency (ƞ). Compared to Cd and Te, FeSi₂ is easier to acquire and less costly. The findings related to this research might thus help manufacturing companies increase their profitability when creating CdTe solar cells. The thickness associated with the NiO window layer ranged from 0.01 μm to 0.35 μm, while all remaining parameters remained constant. To collect data, the SCAPS-1D simulation employed a 0.05 μm thickness variation selected from the given range, which included Voc, Jsc, and FF. Figure 5 displayed the cell output characteristics, illustrating the changes in the NiO window layer’s thickness. The effectiveness associated with the dual absorber (CdTe and FeSi₂) was 26.8%, with FF = 84%, Voc = 0.67 V, and Jsc = 50 mA/cm². The thickness of the NiO layer was 50 nm, the FeSi₂ absorber was 500 nm, and the FTO layer (SnO₂: F) was 40 nm. Without the FeSi₂ absorber layer, the efficiency (ƞ) was computed at 13.26% with Jsc = 25 mA/cm2, Voc = 0.63 V, and FF = 82%.
This picture illustrates how the absorber doping densities for acceptors (a) as well as donors (b) affect the efficiency of ultrathin CdTe solar cells having single (CdTe) as well as dual absorbers (CdTe + FeSi₂). The dual absorber exhibits improved efficiency over most doping ranges. However, at higher doping levels, effectiveness decreases for dual absorbers are observed, underscoring the need of doping concentration optimization.
Cadmium telluride (CdTe) absorber layer NA concentration is changed from 1.0 × 10¹⁰ to 1.0 × 10¹⁹ cm⁻³ for the purpose to predict its impact over the efficiency of CdTe cells. FeSi2 has an electron concentration (NA) of 1 × 10¹⁷, while NiO and SnO2: F have donor concentrations (ND) of 1.0 × 10¹³ and 1.0 × 10¹⁸ respectively. Figure 5(a) illustrates the fluctuation of the numerical aperture (NA) existing in the single absorber (CdTe) layer. When the NA concentration related to CdTe was changed from 10¹⁰ to 10¹⁹, the JSc decreased from 50 mA/cm² to 18 mA/cm², and the Voc increased from 0.65 to 0.94 V. The FF does not change until it reaches 1.0 × 10¹⁵. When the concentration of excess carriers, represented by NA, exceeds 1.0 × 10¹⁵ cm⁻³, it leads to recombination and increased dispersion. This, in turn, reduces the efficiency of the cell with affordable price and rate of production, the most efficient condition for NA (CdTe) is determined to be at 10¹⁰ cm⁻³.
The performance trends observed with varying CdTe acceptor density (NA) can be explained through fundamental device physics. At very low doping levels (e.g., NA = 10¹⁰ cm⁻³), the electric field within the depletion region is weaker, which supports high carrier diffusion but limits open-circuit voltage (Voc) due to a lower built-in potential. This also results in wider space-charge regions and less abrupt band bending, promoting carrier collection but increasing susceptibility to recombination. As NA increases, the built-in electric field becomes stronger, improving charge separation and Voc. However, beyond an optimal point (around 10¹⁵–10¹⁶ cm⁻³), further increase in acceptor concentration leads to enhanced Auger and Shockley–Read–Hall recombination, reducing minority carrier lifetimes and suppressing Jsc. The trade-off between high Voc and low recombination determines the optimal doping range. Thus, the selection of NA = 10¹⁰ cm⁻³ for CdTe in our simulation ensures high Jsc while leveraging a dual absorber structure to compensate for voltage limitations, achieving an effective balance between current gain and voltage retention.
(a) The influence of N_A, and (b) The influence of N_t with both single and double absorber layer.
This image illustrates the effects of both series as well as shunt resistance on ultrathin CdTe solar cells having single (CdTe) as well as dual (CdTe + FeSi₂) absorber layers. A decrease in efficiency is shown in Panel (a), where dual absorbers outperform single absorbers. Higher levels result in greater performance from Panel (b), which shows how resilient the dual absorbers are to changes in resistance by sustaining higher V_oc and short-circuit current density.
The values of R_s as well as R_sh have a significant impact on the characteristics of PV cells. These considerations also dictate the features of the nodes and how they impact the performance of the device. To analyse the dependency of R_s as well as R_sh, the remaining optimised parameters from the previous section were maintained. For this simulation, the values related to Rs as well as R_sh were adjusted among the corresponding ranges of 100–108 Ω-cm² and 0 to 7.0 Ω-cm². The effect of R_s as well as R_sh on the variables affecting a PV cell’s effectiveness is shown in Fig. 6. Figure 7 illustrates how series as well as shunt resistance have a significant effect on solar cell efficacy. The J_sc is more sensitive to higher levels of R_s than R_sh, whereas the V_oc principally focusses on lower values of R_sh other than R_s. When value of R_sh is altered, the fill factor (FF) likewise undergoes a modification. The remaining factors, which includes the width of the absorber layer and width of window layers, and the value of Nt, were kept at their optimal levels as calculated in the previous sections for the purpose to examine the impact of Rs and Rsh. The ideal values related to the series along shunt resistance of PV cell devices on the basis of CdTe as well as FeSi₂ were found to be between 0 and 2.5 Ω-cm₂ and 104 and 107 Ω-cm₂, correspondingly, in this suggested research.
This picture investigates the effects of window layer doping densities on ultrathin CdTe PV solar cells having single (CdTe) as well as dual absorber (CdTe + FeSi₂) layers, paying special attention to acceptor density in panel (b) as well as donor density in panel (a). Efficiency, FF, short-circuit current density, and (:{V}_{OC}) are among the performance metrics that hold steady for both layouts throughout a broad doping range. However, the dual absorber’s somewhat better efficacy highlights its strength beneath various doping conditions.
In Fig. 7(a), the ND donor concentration in the window layer differ as 1.00 × 10¹⁰ cm⁻³ to an unknown parameter at 330 K. A Numerical Aperture (NA) of 1 × 10¹⁰ for a 500 nm CdTe absorber, 1.0 × 10¹⁷ for a 500 nm FeSi₂ absorber, a 55 nm thick NiO layer having a donor concentration (ND) of 10¹³, and a 40 nm thick Fluorine doped Tin Oxide (FTO) layer having an ND of 10¹⁸ cm⁻³ were used for this. The Voc, does not vary as the window layer Nt rises. The value of the (:{V}_{OC}) is 0.66 V. The value of JSC doesn’t change much. The FF value gradually grows from 1 × 10¹⁰ to 1 × 10²⁰, whereas ƞ starts to climb from 10¹⁷ cm to 3. Therefore, after evaluating the total performance, a doping level of 1 × 10¹³ cm⁻³ has been chosen. Figure 7(b) represents the influence of N_t with both single and double absorber.
(a) The influence of series R_s, and (b) The influence of shunt R_sh with both single and double absorber.
(a) The influence of N_D, (b) The influence of N_t with both single and double absorber.
The efficacy related to the ultrathin CdTe solar cells with dual absorbers at the CdTe/FeSi₂ interface (panel a) and the CdTe/In₂S₃ interface (panel b) is investigated in this figure in relation to interface defect density. More recombination losses lead to a drop in efficiency, (:{V}_{OC}), FF, and short-circuit current density. The figure highlights how important it is to lower the interface fault density in dual-absorber configurations in order to get better device effectiveness.
Figure 8 illustrates how the Interface Defect Density (IDD) influences the device’s characteristics. The potential for carrier availability in the junction is enhanced by raising the interface state density (nt) associated with the CdTe as well as NiO, FeSi₂, and CdTe layers. Regional carriers are therefore more likely to be purchased by various local carriers, which lowers efficiency and decreases Jsc. Additional simulations were carried out using nt values ranging from 1.0 × 10¹⁰ cm⁻² to 1 × 10¹⁹ cm⁻² over various active layers in order to forecast the influence of nt over J–V characteristics. The efficiency (ƞ) of the cell exhibits a linear drop with a rise in IDD. As the JSC decreases, the inverse saturation current of the predicted PV cell increases. The suggested design specifies that the resultant data for the CdTe/FeSi₂ and CdTe/NiO interfaces is 10¹⁰ cm⁻³. This figure is optimal considering the reduced cost and increased in the production process.
(a) IDD for CdTe/FeSi2 interface and (b) IDD for CdTe/NiO interface.
This figure investigates the temperature-dependent performance characteristics associated with ultrathin CdTe PV solar cells using single (CdTe) as well as dual absorber (CdTe + FeSi₂) configurations. As temperature rises, efficiency, FF, short-circuit current density, and (:{V}_{OC}) all decrease due to increased carrier recombination as well as decreased carrier mobility. Over the whole temperature range, the dual absorber configuration continuously outperforms the single absorber, demonstrating improved thermal stability as well as efficiency preservation at more temperatures.
As shown in Table 3, the characteristics of CdTe cells with single as well as dual absorbers were evaluated at various temperatures (T) ranging from 280 to 485 K while holding the remaining parameters constant. The effects of temperature changes on Jsc, FF, (:{V}_{OC}), and the ƞ are shown in Fig. 9 for both single (CdTe) as well as double (CdTe + FeSi₂) layer examples. Temperature has a major effect on the characteristics of PV cells because of temperature-sensitive components including Jsc, FF, (:{V}_{OC}), and ƞ. As the reverse saturation current increases and the saturation current rapidly falls as the temperature increases, it is imperative to comprehend that (:{V}_{OC}) fluctuates inversely with T (temperature). The current value determines the saturation parameter, (:{V}_{OC}). The Jsc stays mostly constant as the temperature increases.
PV characteristics due to temperature.
The proposed PV cell architecture exhibits exceptional temperature sensitivity. For low temperatures, the value of ƞ is quite significant. At 275 K, the efficiency, shown by the symbol ƞ, is 29.48%. Nevertheless, at 475 K elevation, the efficiency drops to 12.7%. The efficiency (represented by the symbol ƞ) falls with increasing temperature. Because of temperature-dependent parameters including µh, µn, Eg, and the carrier content in materials, the low value of ƞ̞ is seen at increased temperatures. The efficiency of recombining electron-hole pairs in the unstable Eg decreases as the temperature increases because the Eg values become erratic. The residual short-circuit current (Jsc) remains constant while using a single absorber area made of CdTe or a dual absorber made of CdTe and FeSi₂. The short-circuit current (Jsc) is consistently larger than that of typical structures when FeSi₂ is used as the absorber layer, reaching values of up to 24.2 mA/cm² at all temperature ranges. For basic CdTe cells, Fig. 9 illustrates a notable linear decline in both cell and VOC̞. The overall advantage of employing the FeSi₂ layer in solar cells is demonstrated by the fact that the reduction in these two features is less gradual when the FeSi₂ absorber layer is used.
The decline in power conversion efficiency (PCE) with rising temperature is primarily governed by intrinsic semiconductor behavior. As temperature increases, the intrinsic carrier concentration in the absorber layers rises exponentially, which in turn increases the reverse saturation current (J₀). Since open-circuit voltage (Voc) is logarithmically related to the inverse of J₀, this leads to a noticeable drop in Voc. Additionally, carrier mobility (µn, µp) decreases with temperature due to increased phonon scattering, affecting the drift and diffusion components of current and thereby slightly reducing the fill factor (FF). The bandgap (Eg) of CdTe also narrows with temperature, reducing the energy difference between conduction and valence bands, which adversely impacts charge separation and increases thermal recombination rates. Interestingly, the dual absorber structure incorporating FeSi₂ shows improved thermal robustness compared to CdTe alone. This can be attributed to the superior thermal stability and narrower bandgap of FeSi₂, which helps maintain a higher Jsc across the temperature range by continuing to absorb longer-wavelength photons even under thermal degradation. Thus, while temperature negatively impacts overall performance, the proposed dual-layer architecture shows a slower degradation slope, validating its suitability for real-world applications where temperature variability is inevitable.
In contrast to conventional CdTe-only cells, the dual-absorber structure incorporating FeSi₂ demonstrates enhanced thermal resilience, maintaining a higher Jsc and slower V_oc degradation across the simulated temperature range. This highlights the structural advantage of the proposed configuration in mitigating thermally induced performance loss, suggesting improved reliability and efficiency under real-world conditions involving fluctuating or elevated temperatures.
The density-voltage characteristics related to ultrathin CdTe PV solar cells with single (CdTe) as well as dual absorber (CdTe + FeSi₂) layers are shown in this image. The dual absorber provides a better power conversion efficiency (27.35%) when compared to the single absorber (13.26%) owing to its enhanced short-circuit current density, (:{V}_{OC}), and FF. Better current density as well as voltage characteristics demonstrate the dual absorber’s enhanced functionality as well as potential to increase device effectiveness.
Figure 10 shows the current-voltage characteristics (J-V) of PV cells dependent on CdTe. An overview of the information pertaining to the suggested PV format is shown in Table 3. A thin absorbent layer of 1.00 μm made of a combination of CdTe and FeSi₂ is part of the model. This arrangement is shown to be more efficient than expected for a CdTe PV cell with an absorber consisting of a 0.50 μm thin layer. Yet, the FF has been estimated to increase by 1.31% in proposed cells that incorporate a 0.50 μm thin FeSi2 absorber as opposed to current cells having a 0.50 μm-thin CdTe absorber.Yet, the FF has been estimated to increase by 1.31% in proposed cells that incorporate a 0.50 μm thin FeSi₂ absorber as opposed to current cells having a 0.50 μm-thin CdTe absorber. The value of ƞ̞ is raised by about 14% for this particular analysis. Despite having a thin absorber layer of only 1 μm (CdTe + FeSi₂), Table 3 suggests that the framework proposed in this study might have had greater economic flexibility in comparison to previous CdTe-oriented solar cell models. Utilizing a combination of CdTe and FeSi₂, the configuration also provides a means of reducing the cost of raw materials for solar cell production. Lastly, this suggested PV cell design accomplishes better than earlier versions dependent on CdTe as well as FeSi₂.
The output characteristics of the CdTe-based solar cells.
From the results it can be observed that the proposed design achieved a Voc of 0.656 V when using double absorber which is better than the (:{V}_{OC}) of a single-absorber CdTe-based PV cell attained 0.631 V. This is because FeSi₂ as well as CdTe have an optimal band alignment that reduces recombination losses as well as guarantees effective charge separation. The current density increases from 25.505 mA/cm² to 49.776 mA/cm² with the addition of FeSi₂. This enhanced performance is due to the ability of FeSi2 which absorb photons in the infrared spectrum, which enhances CdTe visible light absorption and improves the device spectral responses. Compared to all the other existing methods, the performance of proposed design in better and ensures minimal material usage without compromising the device’s performance addressing both cost and sustainability concerns.
This work demonstrates the viability of an ultrathin CdTe-based solar cell enhanced with an FeSi₂ secondary absorber layer using numerical simulations via SCAPS-1D. The proposed structure achieves a high-power conversion efficiency of 27.35% with a total absorber thickness of just 1.0 μm (0.5 μm CdTe + 0.5 μm FeSi₂), outperforming conventional single-junction CdTe designs. Unlike prior studies, this dual-layer configuration exploits complementary absorption spectra and favorable band alignment to enhance both Jsc and Voc while minimizing material usage. Device optimization across parameters including absorber thickness, doping density, and window layer thickness reveals performance gains rooted in physical carrier dynamics. Furthermore, temperature-dependent simulations indicate a slower degradation slope in efficiency for the dual-absorber cell, confirming its thermal robustness. These results not only validate the design concept but also point to a promising direction for next-generation, cost-effective, and scalable thin-film photovoltaics. Future experimental studies are encouraged to verify the thermal stability and interface quality of the proposed heterostructure.
Full name of software and Version number-SCAPS (Solar Cell Capacitance Simulator)−1D version 3.3.10 URL link – https://scaps.elis.ugent.be/.
Data supporting this study is provided within the manuscript.
Hole Mobility
Electron Mobility
Cadmium Telluride
Energy Band Gap
External Quantum Efficiency
Iron Silicide
Silicon Material
Fill Factor
Fluorine-Doped Tin Oxide
Efficiency
Nickel
Interface Defect
Defect Density
Power Conversion Efficiency
Photovoltaic
Quantum Efficiency
Series Resistance
Shunt Resistance
Voltage (Open-Circuit)
Electron Affinity
Acceptor Density
Donor Density
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Department of Electrical and Electronics Engineering, Mahendra Engineering College, 637503, Namakkal, Tamil Nadu, India
P. Parathraju & P. Umasankar
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Parathraju, P., Umasankar, P. Performance evaluation of ultrathin CdTe-based solar cells with dual absorbers via SCAPS-1D simulation. Sci Rep 15, 26428 (2025). https://doi.org/10.1038/s41598-025-12006-6
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Received: 26 February 2025
Accepted: 14 July 2025
Published: 21 July 2025
Version of record: 21 July 2025
DOI: https://doi.org/10.1038/s41598-025-12006-6
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