Damp heat–stable perovskite solar cell with 24.3% efficiency

Scientists led by Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) have developed a perovskite solar cell based on a 2D/3D perovskite heterojunction that is claimed to retain over 95% of its initial efficiency after 1,000 hours at damp-heat test conditions.

“The study is not the first focusing on damp-heat passing perovskite solar cells, but it is the first to report an efficiency exceeding 20% after the damp-heat test, with industry compatible encapsulation methods,” the research's corresponding author, Erkan Aydin, told pv magazine.

The special heterojunction was fabricated by growing two-dimensional (2D) perovskite layers on the top surface of a 3D-perovskite, which is claimed to ensure defect passivation and eliminate ion migration. These layers were embedded between the 3D-perovskite surface and the opaque hole-selective top-contact stack. The 2D-perovskite fragments were dimensioned by tuning the annealing conditions with higher temperatures. This resulted in more efficient charge transfer at the 2D/3D perovskite interface and the electron-selective layer. “In addition, the effects of 2D-perovskite capping layers also enhanced the resilience against moisture of 3D-perovskite film,” the scientists highlighted.

The cell was fabricated with a substrate made of glass and indium tin oxide (ITO), the 2D layers, the 3D perovskite layer, an electron-selective layer, a buffer layer based on bathocuproine (BCP), and silver metal contact.

The device achieved a power conversion efficiency of 24.7%, an open circuit voltage of approximately 1.20 V, and fill factor of around 82%. “Our 2D-perovskite passivation simultaneously served as ion-migration-blocking, moisture-oxygen ingress barriers, and defect passivation layers, particularly at elevated operating temperatures,” the research team emphasized. “Our results represent the successful encapsulation of PSCs passing industry-relevant damp-heat test according to the IEC 61215:2016 protocol.”

According to the academics, the cell was able to achieve an efficiency of over 19% after 1,000 hours of damp-heat test. “There was no substantial change in the structural and optical properties of the 2D-perovskite passivation films (both 3D and 2D perovskites) after over 500 hours thermal annealed at 85 degrees Celsius, confirming the robustness of our 2D-perovskite passivation approach,” they concluded.

The solar cell is described in the paper Damp heat — stable perovskite solar cells with tailored-dimensionality 2D/3D heterojunctions, published in Science.