Thiourea Suppressing Iodide Oxidation and Passivating Perovskite Surface to Achieve High‐Efficiency Stable Solar Cells

Abstract Metal halide perovskite solar cells (PSCs) have witnessed their power conversion efficiency (PCE) record continuously refreshed over the last two decades. The device long‐term stability however remains as the critical consideration for their industrialization. In particular, the redox‐sensitive ions and precursors can easily initiate reaction, leading to perovskite lattice segregation and defect formation and thus instability of PSCs. In this work, a versatile perovskite film stabilizing method is reported here using 1‐(3‐(trifluoromethyl)phenyl) thiourea (TPT) as a redox modifier to achieve high‐efficiency and stable PSCs. Featuring large dipole moments, TPT performs excellent antioxidation for iodides and constructs multiple interactions with FA + and Pb 2+ cations to dramatically reduce defect state density as well as modulate surface potential in perovskite film. The TPT‐modified perovskite films readily endow the inverted PSCs with a highest PCE of 24.71% in 0.12 cm 2 device area and a superior fill factor of 84.59%, together with an excellent device stability against moisture and oxygen. Over 88% retention of initial PCE has been achieved after 2000 h aging in ambient air with 30%–40% relative humidity. This thiourea stabilizing perovskite strategy is expected to benefit large‐area fabrication of PSCs for simultaneously achieving high performance in both power output and long‐term stability.