Controlling Lead Halide Residue in Perovskite Solar Cells: A Method to Improve the Photostability and Hysteresis

Perovskite solar cells (PSCs) have gained considerable attention due to their exceptional power conversion efficiencies and potential for low-cost manufacturing.Spin coating technique is usullay employed for fabrication of perovskite films in small area devices. Among various spin coating techniques, the two-step spin-coating process is commonly used to fabricate high-efficiency solar cells, but it often leaves unreactive lead iodide in the perovskite films, which can both enhance and impair PSC performance depending on their amount. In this study, four sets of perovskite films and devices were fabricated using the two-step spin-coating process under different processing conditions. While all conditions resulted in promising power conversion efficiencies (PCE>20%), the photostability of the devices was significantly influenced by the amount of unreacted lead iodide in the films. Varying levels of residual lead iodide were detected, and upon light exposure, this lead iodide decomposed into metallic lead (Pb⁰) and mobile iodine, which adversely affected photovoltaic performance. The presence of mobile ions in metal–halide perovskites resulting in hysteresis in the J–V curves, with perovskite films containing Pb⁰ exhibiting pronounced inverted hysteresis. This work highlights the dual role of lead iodide in boosting efficiency while presenting challenges to the long-term stability of PSCs.
Reference
Kalasariya, N., Alexander, A., Bhunia, P.K., Gutierrez-Partida, E., Benny, R., Stolterfoht, M. and Namboothiry, M.A.G. (2024), Controlling Lead Halide Residue in Perovskite Solar Cells: A Method to Improve the Photostability and Hysteresis. Sol. RRL, 8: 2300788