An international research team has fabricated perovskite solar cells and modules with a 2D/3D heterojunction architecture through a new manufacturing technique that reportedly improves device stability and efficiency.
Perovskite cells built with 2D hybrid materials are generally more stable than conventional, 3D devices, due to the protection provided by the organic ligands. They usually exhibit large exciton binding energies.
“We developed a new room-temperature crystallization method, termed selective iodoplumbate cold casting (SICC), that enables kinetically stabilized perovskite phases inaccessible through conventional thermodynamic processing,” corresponding author Aditya D. Mohite told pv magazine. “This strategy produces uniform 2D layers that enhance out-of-plane charge transport in 3D:2D bilayer devices, achieving over 25% efficiency in cells and over 22% efficiency in large-area photovoltaic modules.”
In the study “Selective iodoplumbate cold casting for kinetically stabilized perovskites leading to high-efficiency photovoltaic modules,” published in nature syntesis, the researchers explained that, in 2D perovskites, kinetically favored phases are often overlooked because fabrication methods are adapted from thermodynamically driven 3D perovskite processing. SICC, in contrast, controls precursor chemistry through solvent design. “Using SICC, we realized unusual low-dimensional perovskite crystal structures, including a corrugated MA₂PbI₄ phase that has been difficult to access in methylammonium-based systems,” Mohite added. “The SICC process selectively forms simplified iodoplumbate species, enabling rapid and highly phase-pure crystallization without thermal annealing.”
By mixing solvents with different donor numbers, particularly acetonitrile and N-methyl-2-pyrrolidone (NMP), the researchers selectively promote the formation of the iodoplumbate species. Spectroscopic analyses confirmed that SICC more effectively controls precursor structures than organic cations themselves. “Unlike conventional low-n 2D perovskites that suffer from insulating horizontal alignment, the SICC films provide efficient vertical carrier transport and favorable band alignment with 3D perovskites,” Mohite emphasized. “The SICC-grown 2D layers significantly improve the quality and uniformity of 3D:2D heterostructures, enabling enhanced efficiency, reduced hysteresis, and improved operational stability.”
Through the proposed technique, the researchers developed a perovskite solar cell with an active area of 0.094 cm² and a device architecture comprising a fluorine-doped tin oxide (FTO) substrate, a tin oxide (SnO₂) electron transport layer (ETL), a 3D perovskite absorber, a 2D perovskite layer, a hole transport layer (ETL) relying on Spiro-OMeTAD), and a gold (Au) electrode. To create the 3D/2D bilayer heterostructure, the scientists integrated a butylammonium lead iodide (BA₂PbI₄) 2D perovskite layer via a solid-state in-plane growth process.
The champion cell had an . The bilayer structure was formed by pressing separately prepared 2D and 3D perovskite films together at a pressure of 60 MPa and temperatures ranging from 60 C to 85 C.
For scale-up, the team fabricated mini-modules on 7.1 cm × 7.1 cm substrates. Each module consisted of 10 monolithically interconnected subcells and had an active area of 25 cm². Interconnection was achieved through P1, P2, and P3 laser scribing using a 532 nm picosecond laser. The optimized patterning process resulted in a geometric fill factor of 94.36%, with scribe widths of 25 μm, 120 μm, and 110 μm for the P1, P2, and P3 lines, respectively.
The devices were tested under standard AM1.5G illumination at 100 mW/cm². The researchers reported a power conversion efficiency of 25.14% for the small-area cell and 22.36% for the 25 cm² mini-module. For stability testing, the modules were encapsulated with a 1.1 mm-thick glass cover using a UV-curable resin and maintained more than 90% of their initial performance for over 1,000 hours under continuous one-sun operation.
“Our findings suggest that low-dimensional perovskites should be understood and engineered as kinetic products rather than purely thermodynamic materials,” Mohite concluded. “Our work provides a scalable pathway for integrating stable low-dimensional perovskites into next-generation high-efficiency solar modules and tandem photovoltaics.”
The research team included academics from South Korea’s Seoul National University, the Korea Institute of Industrial Technology, Korean perovskite start-up Frontier Energy Solution (FES), Rice University and Northwestern University in the United States, as well as from France’s Institut Fonctions Optiques pour les Technologies de l’Information.
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