Thickness optimization of SnO2 electron transporting layer in perovskite solar cells assembled under ambient atmosphere

Perovskite solar cells (PSCs) were assembled in ambient environment using different SnO2 electron transporting layers (ETLs) to explore the optimized SnO2 thickness. For this purpose, All PSCs had the low-cost architecture of FTO/b-TiO2 (block-TiO2)/SnO2/m-TiO2 (mesoporous-TiO2)/MAPbI3 (CH3NH3PbI3)/CIS (CuInS2)/carbon cathode. The influence of the SnO2 layer thickness was investigated onto the PSCs performances. The solar cell fabricated by L1-SnO2 layer had a thickness of about 582 nm and the SnO2 film thickness enlarged as the number of SnO2 layers was increased. The optimum ETL was achieved via deposition of one SnO2 layer (L1), which exhibited a uniform, hole‐free, and compact film surface. The champion PSC device fabricated with L1 SnO2 layer displayed the biggest average power conversion efficiency (PCE) of 12.60%, which was nearly 1.75 times larger than the average PCE= 7.19% for the champion SnO2-free device. As the SnO2 film thickness decreased, the PSC efficiency diminished so that the lowest PCE= 6.29% was measured for the device based on the L5-SnO2 ETL. The EIS spectra verified the lowest recombination of charge carriers and the most efficient charge extraction at L1 ETL and perovskite layer interface among all devices. As a result, the PSC with L1 SnO2 layer could be applied to fabricate economical and efficient PSC devices.