Dual Optimization via Doping PCBM with Diamine for Efficient Pure-Iodide Wide-Bandgap Perovskite Solar Cells

The excellent photostability of pure-iodide wide-bandgap (WBG) perovskite solar cells (PSCs) makes them ideal candidates for tandem and indoor photovoltaics. However, the efficiency is significantly restricted by interfacial charge transfer and recombination behaviors. Here, highly efficient pure-iodide WBG PSCs achieved through a dual optimization strategy for the perovskite/PCBM interface is presented. The PCBM/chlorobenzene solution, doped with propanediamine iodine (PDAI2)/isopropanol solution, is deposited onto the Cs0.4DMA0.2FA0.2MA0.2PbI3 perovskite layer. The presence of isopropanol notably improves the wetness of the PCBM solution, which is beneficial for depositing a smooth PCBM layer and economizing on the material. Most importantly, the PDAI2 in PCBM not only passivates perovskite surface defects to suppress non-radiative recombination but also induces n-type doping for PCBM to enhance its carrier mobility and elevate the Fermi level with better energy level matching, thereby reducing energy loss and facilitating electron transfer. These benefits result in overall photovoltaic improvements, achieving a high efficiency of 21.84%, while retaining 92% of its initial efficiency after 1500 h of continuous illumination. Furthermore, when applied under indoor light illumination (1000 lux, 280 mu W cm-2), the best cell demonstrates an impressive efficiency of 41.05%.