Mitigating voltage loss in efficient CsPbI2Br all-inorganic perovskite solar cells via metal ion-doped ZnO electron transport layer.

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 (V_OC) 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 V_OC 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 V_OC 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 V_OC deficit toward the attainment of highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]