Two-step processed efficient perovskite solar cells via improving perovskite/PTAA interface using solvent engineering in PbI₂ precursor

The morphology and interface of perovskite film are very important for the performance of perovskite solar cells (PSCs). The quality of perovskite film, fabricated via two-step spin-coating process, is significantly influenced by the morphology and crystallinity of PbI₂ film. With the addition of additive dimethyl sulfoxide (DMSO) into the PbI₂ precursor, the roughness and trap-state density of perovskite film have been significantly reduced, leading to the excellent contact between perovskite layer and subsequent deposited carrier transport layer. Accordingly, the planar heterojunction PSCs with an architecture of ITO/SnO₂/perovskite/PTAA/Ag show an efficiency up to 19.02%. Furthermore, PSCs exhibit promising stability in air with a humidity of ～ 45%, and retain 80% of initial efficiency after being exposed to air for 400 h without any encapsulation.