Ultra-High 1.27 V <i>V</i><sub>OC</sub> of\nPure CsPbI<sub>3</sub> Perovskite Solar Cells with an Efficiency of\n21.8%

There\nare a large number of Pb-related defects in CsPbI<sub>3</sub> perovskite\ndue to the easy migration of halogen ions, which cause\nsevere non-radiative recombination, leading to huge open circuit voltage\n(<i>V</i><sub>OC</sub>) loss and power conversion efficiency\n(PCE) loss for CsPbI<sub>3</sub> perovskite solar cells (PSCs). Herein,\nefficient and stable CsPbI<sub>3</sub> PSCs are obtained by introducing\na chlorosilane molecule (1,2-bis(chlorodimethylsilyl)ethane, CSE)\ninto a perovskite precursor. CSE can effectively passivate the Pb-related\ndefects, inhibit the non-radiative recombination, and adjust the energy\nlevel arrangement of PSCs to reduce the <i>V</i><sub>OC</sub> loss. The champion CsPbI<sub>3</sub> PSC achieves a high PCE of\n21.8% and an amazing <i>V</i><sub>OC</sub> of 1.27 V. In\naddition, the hydrolytic polymerization of CSE molecules builds a\nmoisture barrier, which increases the stability of CsPbI<sub>3</sub> PSCs. The unencapsulated CsPbI<sub>3</sub> PSCs retain 90% of the\ninitial PCE after storage in air for 1500 h; the encapsulated device\nretains 97% of the initial PCE after operation under continuous illumination\nfor 440 h.