Li-Doped Chemical Bath Deposited SnO2 Enables Efficient Perovskite Photovoltaics

Electron transport layers (ETLs) based on tin oxide (SnO2) get wide attention in planar perovskite solar cells (PSCs), with the merits of high electron mobility and low-temperature fabrication. However, the poor electron extraction ability of SnO2 seriously deteriorates the performance of devices. Herein, we report an optimized strategy for SnO2 films to enhance the carrier transport. The dense and pinhole free ETL films with Li doping are developed by chemical bath deposition. Li-doped SnO2 shows better energy band alignment between ETLs and perovskite layers, which facilitates the electron extraction and reduces recombination loss. On the basis of the above improved performances, the PSCs with Li-doped SnO2 have achieved an improved power conversion efficiency (PCE) over 22%. The unencapsulated devices show excellent stability, and the PCE exhibits almost no change after 800 h storage.