Ultra-High 1.27 V VOC of Pure CsPbI3 Perovskite Solar Cells with an Efficiency of 21.8%

There are a large number of Pb-related defects in CsPbI 3 perovskite due to the easy migration of halogen ions, which cause severe non-radiative recombination, leading to huge open circuit voltage ( V OC ) loss and power conversion efficiency (PCE) loss for CsPbI 3 perovskite solar cells (PSCs). Herein, efficient and stable CsPbI 3 PSCs are obtained by introducing a chlorosilane molecule (1,2-bis(chlorodimethylsilyl)ethane, CSE) into a perovskite precursor. CSE can effectively passivate the Pb-related defects, inhibit the non-radiative recombination, and adjust the energy level arrangement of PSCs to reduce the V OC loss. The champion CsPbI 3 PSC achieves a high PCE of 21.8% and an amazing V OC of 1.27 V. In addition, the hydrolytic polymerization of CSE molecules builds a moisture barrier, which increases the stability of CsPbI 3 PSCs. The unencapsulated CsPbI 3 PSCs retain 90% of the initial PCE after storage in air for 1500 h; the encapsulated device retains 97% of the initial PCE after operation under continuous illumination for 440 h.