Reduced Open‐Circuit Voltage Loss of Perovskite Solar Cells via Forming p/p+ Homojunction and Interface Electric Field on the Surfaces of Perovskite Film

Abstract The severe nonradiative recombination losses limit the further improvement of open‐circuit voltage ( V oc ) and power conversion efficiency (PCE) of perovskite solar cells (PVSCs). In this work, the 4,4′‐cyclohexylidenebis N , N ‐bis(4‐methylphenyl) benzene amine is dissolved into the antisolvent to prepare perovskite films, which reduces defects, improves the crystallinity, and induces a p/p + homojunction on the top surface of perovskite film. Besides, the 2‐thiophenemethylammonium iodide and 2‐thiophenethylammonium iodide form interface electric field and passivate defects on the bottom surface of perovskite film. The p/p + homojunction and interface electric field enhance the charges’ separation and transportation efficiencies in the bulk perovskite film and at the perovskite/charge transport layer interfaces, which effectively reduces nonradiative recombination losses and V oc loss of PVSCs. Consequently, low V oc loss of 0.348 V is realized, resulting in the increase in V oc from 1.082 to 1.172 V and PCE from19.15% to 23.44%. The optimized PVSCs without encapsulation maintain 88.23% of the original PCE after exposing in the air for 1500 h. This work provides a strategy to reduce the nonradiative recombination losses and V oc loss by forming p/p + homojunction and interface electric field on the surfaces of perovskite film, which advances the development of high‐performance PVSCs.