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

The severe nonradiative recombination losses limit the further improvement of open‐circuit voltage (Voc) 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 Voc loss of PVSCs. Consequently, low Voc loss of 0.348 V is realized, resulting in the increase in Voc 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 Voc loss by forming p/p+ homojunction and interface electric field on the surfaces of perovskite film, which advances the development of high‐performance PVSCs.