Stabilizing γ-CsPbI₃ Perovskite via Phenylethylammonium for Efficient Solar Cells with Open-Circuit Voltage over...

Cesium lead iodide (CsPbI₃ ) perovskite has gained great attention due to its potential thermal stability and appropriate bandgap (≈1.73 eV) for tandem cells. However, the moisture-induced thermodynamically unstable phase and large open-circuit voltage (V_OC ) deficit and also the low efficiency seriously limit its further development. Herein, long chain phenylethylammonium (PEA) is utilized into CsPbI₃ perovskite to stabilize the orthorhombic black perovskite phase (γ-CsPbI₃ ) under ambient condition. Furthermore, the moderate lead acetate (Pb(OAc)₂ ) is controlled to combine with phenylethylammonium iodide to form the 2D perovskite, which can dramatically suppress the charge recombination in CsPbI₃ . Unprecedentedly, the resulted CsPbI₃ solar cells achieve a 17% power conversion efficiency with a record V_OC of 1.33 V, the V_OC deficit is only 0.38 V, which is close to those in organic-inorganic perovskite solar cells (PSCs). Meanwhile, the PEA modified device maintains 94% of its initial efficiency after exceeding 2000 h of storage in the low-humidity controlled environment without encapsulation.