TiO2/SnO2 electron transport double layers with ultrathin SnO2 for efficient planar perovskite solar cells

Abstract

The electron transport layer (ETL) plays an important role on the performance and stability of perovskite solar cells (PSCs). Developing double ETL is a promising strategy to take the advantages of different ETL materials and avoid their drawbacks. Here, an ultrathin SnO2 layer of ∼ 5 nm deposited by atomic layer deposit (ALD) was used to construct a TiO2/SnO2 double ETL, improving the power conversion efficiency (PCE) from 18.02% to 21.13%. The ultrathin SnO2 layer enhances the electrical conductivity of the double layer ETLs and improves band alignment at the ETL/perovskite interface, promoting charge extraction and transfer. The ultrathin SnO2 layer also passivates the ETL/perovskite interface, suppressing nonradiative recombination. The double ETL achieves outstanding stability compared with PSCs with TiO2 only ETL. The PSCs with double ETL retains 85% of its initial PCE after 900 hours illumination. Our work demonstrates the prospects of using ultrathin metal oxide to construct double ETL for high-performance PSCs.