Two-step solvent post-treatment on PTAA for highly efficient and stable inverted perovskite solar cells

Modifying the surface of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with toluene during the high-speed spin-coating process of dimethylformamide considerably improves the wettability and morphology of PTAA and results in improvement of the crystallinity and absorption of perovskite film. The hole mobility and ohm contact have also been improved accordingly. Combined with these improved parameters, inverted perovskite solar cells with high efficiency of 19.13% and long-term stability could be achieved, which are much better than those with untreated PTAA. Importantly, our devices can keep 88.4% of the initial power conversion efficiency after 30 days of storage in ambient air.