Enhancement of the performance of planar perovskite solar cells by active-layer surface/interface modification with optimal mixed solvent-antisolvent post-treatment

Modification of perovskite films surface/interface through the solvent vapor post-treatment during the film annealing can significantly improve the morphology and crystallinity of the perovskite film, thus enhances the efficiency of the perovskite solar cells (PSCs). In this work, we used a solvent-antisolvent mixture of Dimethyl sulfoxide (DMSO) and chlorobenzene (CB) in the post-treatment of perovskite films during device fabrication to achieve a high-power conversion efficiency of 19.15% in planar perovskite solar cells. The use of chlorobenzene as an additive to DMSO in the post-treatment of the perovskite films was shown to optimize the its morphology and resulted in films with highly fused grains. The modified perovskite film surface not only showed a decreased number of pin-hole and trap density at the surface, but also an increase in the charge transfer at the interfaces and reduced the susceptibility to low-frequency interface polarization. Furthermore, the impedance spectroscopy and I–V characteristics of the electron-only PSC devices also verified the conclusions above. Overall, this work demonstrates mixed solvent-antisolvent post-treatments of perovskite films as an effective modification strategy to tune their surface/interface properties. This approach is anticipated to be extrapolated to other categories of polycrystalline bulk materials and devices.