Defect passivation of CsPbI₂Br perovskites through Zn(II) doping: toward efficient and stable solar cells

Defect passivation is an important strategy to achieve perovskite solar cells (PVSCs) with enhanced power conversion efficiencies (PCEs) and improved stability because the trap states induced by defects in the interfaces and grain boundaries of perovskites are harmful to both large open circuit voltage and high photocurrent of devices. Here, zinc cations (Zn²⁺) were used as a dopant to passivate defects of the CsPbI2Br perovskite leading to Zn²⁺-doped CsPbI₂Br film with fewer trap states, improved charge transportation, and enhanced light-harvesting ability. Thus, the best-performance PVSC based on CsPbI2Br with the optimal Zn²⁺ doping shows a higher PCE of 12.16% with a larger open-circuit voltage (V_OC) of 1.236 V, an improved shortcircuit current (JSC) of 15.61 mA cm⁻² in comparison with the control device based on the pure CsPbI₂Br which exhibits a PCE of 10.21% with a V_OC of 1.123 V, a J_SC of 13.27 mA cm⁻². Time-resolved photoluminescence results show that the Zn²⁺ doping leads to perovskite film with extended photoluminescence lifetime which means a longer diffusion length and subsequently enhanced photocurrent and open circuit voltage. This work provides a simple strategy to boost the performance of PVSCs through Zn²⁺ doping.