The proposed inverted perovskite solar cell design reduces band misalignment and electron accumulation, suppressing recombination losses and enabling high efficiency in both small-area devices and scalable modules.
Image: Nankai University
Researchers from Nankai University and Beijing Institute of Technology in China claim to have achieved a world record power conversion efficiency for a perovskite solar cell with an inverted architecture.
Inverted perovskite cells have a device structure known as “p-i-n”, in which hole-selective contact p is at the bottom of intrinsic perovskite layer i with electron transport layer n at the top. Conventional halide perovskite cells have the same structure but reversed – a “n-i-p” layout. In n-i-p architecture, the solar cell is illuminated through the electron-transport layer (ETL) side; in the p-i-n structure, it is illuminated through the hole‐transport layer (HTL) surface.
Although inverted perovskite solar cells have shown rapid efficiency gains in recent years, these devices still lag behind n-i-p counterparts, due to persistent non-radiative recombination losses occurring at the textured interface between the ETL and the perovskite absorber. “Previous reseach had struggled to identify the physical mechanisms driving these losses,” the research team explained. “With our work, we showed that energy-band misalignment and electron accumulation at the buried interface act together to accelerate carrier trapping and interfacial recombination, ultimately limiting device efficiency.”
The scientists investigated, in particular, the interaction between an ETL made of tin oxide (SnO₂) and the perovskite interface. They found that lattice mismatch and electron accumulation jointly increase non-radiative recombination, reducing cell efficiency.
The group then examined the growth mechanism of chemically bath-deposited SnO₂ films and established links between ligand chemistry, oxygen vacancy concentration, and the material’s energy band structure. Based on these findings, they developed a “ligand competition and combination control” strategy to fabricate a continuously gradient-doped SnO₂ ETL featuring a transition from a lightly doped region to a heavily doped region.
“This graded architecture simultaneously minimizes band offset and accelerates electron extraction, thereby effectively suppressing the cross-interface recombination,” the academics explained, noting that the proposed cell structure successfully transitions from a lightly doped n-region near the perovskite interface to a heavily doped region farther away, helping to reduce interfacial mismatch and electron accumulation simultaneously.
Tested under standard illumination conditions, the solar cell achieved a certified power conversion efficiency of 27.17%, setting a new efficiency record for the inverted device architecture. The device also delivered a reverse-scan efficiency of 27.50%, meaning it reached an even higher efficiency when the current–voltage measurement was performed by scanning from high voltage to low voltage. Researchers often report both forward- and reverse-scan values for perovskite solar cells because the technology can exhibit hysteresis, where measured performance varies depending on the scan direction and measurement conditions.
The researchers also achieved a power conversion efficiency of 25.79% for a 1 cm² single-junction device, indicating that the interfacial engineering approach remains highly effective at the laboratory scale. They also fabricated a larger perovskite module with a 16.02 cm² aperture area, which delivered an efficiency of 23.33%.
“Our research has dispelled the longstanding ‘performance fog’ surrounding formal structural devices at the mechanistic level, opening a universal and effective new pathway for the rational design of electron transport layers in inverted perovskite devices,” the academics concluded. “This development is expected to provide technical support for the high stability and scalable production of perovskite photovoltaic modules.”
The new solar cell design was presented in “Continuously graded-doped SnO₂ for efficient n–i–p perovskite solar cells,” published in nature.
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