Solvent‐Additive Engineering‐Assisted Improvement of Interface Contact for Producing Highly Efficient Inverted Perovskite Solar Cells

Inverted perovskite solar cells (IPSCs) suffer from perishing interface contact due to the non‐wetting hole‐transport layer (HTL). Herein, the several classes of solvent to the perovskite precursor (the process is defined as solvent‐additive engineering) for achieving an improvement in the interface contact between nonwetting HTL and active perovskite layer, suitably achieving improved hole‐interface charge transfer, are mixed. Also, a high‐quality perovskite layer with high crystallinity, large grain distribution, and flat surface morphology is obtained based on solvent‐additive engineering, which affords a lower bulk and interface trap density. IPSCs with the modified perovskite layer show suppression of nonradiative recombination on the surface and in the bulk of the perovskite, thereby achieving an outstanding power conversion efficiency of 20.6%. In addition, IPSCs using a mixed‐cation perovskite (FA_0.83Cs_0.07MA_0.13PbI_2.64Br_0.39) are also fabricated and a highest efficiency of 22.1%, visualizing the broad applicability of this method, is achieved. This simple, low‐cost, and efficient solvent‐additive strategy can solve interface contact problems and improve perovskite quality, thus potentially giving rise to other applications.