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An inorganic CsPbI2Br perovskite has garnered significant interest due to its outstanding photoelectrical properties in recent years. However, CsPbI2Br-based perovskite solar cells (PSCs) generally suffer from large energy loss, hindering their further development. Herein, we proposed a facile and effective approach to dope the ZnO electron transporting layer (ETL) with alkaline earth metal ions to boost the photovoltaic performance of CsPbI2Br PSCs. Particularly, the ZnO ETL doped with Ca2+ can simultaneously ameliorate electron transport, energy level alignment, and the quality of the upper CsPbI2Br film, thus resulting in faster charge extraction and suppressed charge recombination. Consequently, the ZnO:Ca-based PSC achieves a champion power conversion efficiency (PCE) of 16.39% with an excellent VOC of 1.292 V, while the control ZnO-based PSC just exhibits an inferior PCE of 14.22% with a VOC of 1.178 V. Furthermore, the ZnO:Ca-based devices also present considerable enhancements in device stability without encapsulation. Our work offers a promising strategy to mitigate the energy loss toward efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

CsPbI2Br all-inorganic perovskite solar cells (PSCs) have attracted much attention due to their suitable bandgap and outstanding thermostability. However, the large energy loss of CsPbI2Br PSCs generally endows low open circuit voltage (VOC) and unsatisfactory power conversion efficiency (PCE), which severely hamper its further development. Herein, we proposed a facile route to modify the ZnO electron transporting layer (ETL) by in situ chemical doping strategy with metal ions. The doped ZnO ETL with Pb(Ac)2 or CsAc cannot only effectively tune its energy levels, conductivity, and charge extraction but also ameliorate the crystallization and morphology of upper perovskite films. Particularly, Pb(Ac)2-doped ZnO (ZnO:Pb) induces an energy level offset of 0.15 eV relative to the conduction band of CsPbI2Br with largely reduced Ohmic loss. Thus, the highest VOC is significantly boosted to above 1.3 V for the CsPbI2Br PSCs with a champion PCE of 16.36%, while the reference PSC just yields a moderate PCE of 14.43% with a low VOC of 1.168 V. Moreover, considerable improvements in device stability are achieved for the PSCs with doped ZnO ETLs than those of the ZnO-based device. Our work provides a promising strategy to alleviate the VOC deficit toward the attainment of highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]