Benefits of fullerene/SnO2 bilayers as electron transport layer for efficient planar perovskite solar cells

Abstract The low temperature-processed electron transport layers are crucial to the commercial perovskite solar cells (PSCs). PC 60 BM/SnO 2 bilayer electron transport layer (ETL) has gradually been reported, but the mechanism of enhancement by the introducing PC 60 BM on SnO 2 is not fully understudied. In this work, low temperature PC 60 BM/SnO 2 bilayer ETLs are successfully prepared via a solution process. The introduction of PC 60 BM dramatically enhances the performance of the planar PSCs, and the reason has been systemically investigated. The results show that the existence of PC 60 BM could enhance the crystalline quality and grain boundary integration in perovskite films. The J-V analysis, absorption spectra, photoluminescence spectra and time-resolved photoluminescence spectra show that both the light harvesting of perovskite films and carrier extraction from perovskite films to PC 60 BM/SnO 2 bilayer have been enhanced. Otherwise, perovskite films on ITO/SnO 2 /PC 60 BM substrate have a lower trap state density and higher electron mobility than those of ITO/SnO 2 substrate or bare ITO substrate. All the results suggest that low temperature-processed PC 60 BM/SnO 2 ETLs will benefit the performance of PSCs and promote the commercial application of planar PSCs.