Performance Enhancement of Inverted Perovskite Solar Cells Based on Smooth and Compact PC61BM:SnO2 Electron Transport Layers

In this work, PC61BM:SnO2 electron transport layers (ETLs) were applied in inverted CH3NH3PbI3 perovskite solar cells, and a high power conversion efficiency of 19.7% could be obtained. It increased by 49.0% in comparison with the device based on PC61BM-only ETL (13.2%). SnO2 nanocrystals with excellent dispersibility were employed here to fill the pinholes and cover the valleys of PC61BM layer, forming smooth and compact PC61BM:SnO2 layers. Simultaneously, the electron traps caused by deep-level native defects of SnO2 were reduced by PC61BM, proved by the space charge limited current analysis. Thus, PC61BM:SnO2 ETLs can inhibit both of the defects in PC61BM and SnO2 layers which contribute to the electron transport improvement and reduce the recombination loss. Moreover, the device stability based on the bilayer was significantly improved in comparison with the PC61BM-only device and the performance of 85% could be maintained after 1 month.