A Mixed Antisolvent-Assisted Crystallization Strategy for Efficient All-Inorganic CsPbIBr₂ Perovskite Solar Cells by a Low-Temperature Process

To improve the microstructure of low-temperature-processed CsPbIBr2 films, a chlorobenzene (CB) and isopropyl alcohol (IPA) mixed solution is used as an antisolvent to fabricate CsPbIBr2 films. It is found that the modified film by the mixed antisolvent demonstrates a better morphology, crystallinity, absorption of sunlight, less trap-state density (Ntrap), and suppressed carrier recombination. The modified perovskite solar cells (PSCs) without a hole-transport layer (HTL) achieve a champion efficiency of 7.05%, being much higher by 28.18% than that of the Reference-PSCs without an antisolvent. Moreover, the HTL of undoped zinc phthalocyanine (ZnPc) prepared by solution processing is used to promote charge transfer and protect the CsPbIBr2 film from damage caused by humid air at the CsPbIBr2/carbon interface. The best PSC with a structure of FTO/TiO2/CsPbIBr2/ZnPc/carbon yields a champion efficiency of 8.48% (Reference-PSC, 5.50%) with an open-circuit voltage of 1.23 V. The modified PSCs without encapsulation demonstrate improved humidity stability and retain about 90% (Reference-PSC, ∼70%) of their initial efficiency after storage at a 20% relative humidity in air for 30 days. In addition, the modified PSCs possess good light and thermal stability. Our work provides a feasible low-temperature (150 °C) process to prepare CsPbIBr2 films with the preferred orientation and stable, efficient all-inorganic PSCs (200 °C).