Self-Healing Significantly Improves Performances of\nNiO Sputtered <i>n‑i‑p</i> Perovskite Solar\nCells

Using\nradio frequency magnetron sputter deposition to apply metal\noxide thin film as a hole transporting layer (HTL) onto a halide perovskite\nlayer significantly compromises the device photovoltaic performance.\nTherefore, despite its economic advantages and scalability potential,\nthis method is generally not favored. Herein, we identify the primary\ncause of this limitation as the loss of the organic moiety from the\nnear-interface region during the sputter deposition of NiO onto the\nhalide perovskite and the consequent generation of interfacial defects.\nFurthermore, we show that a self-healing process, without any external\nintervention, is able to significantly compensate for the adverse\neffects of the sputtering process, resulting in the device efficiency\nto 180–220% of its initial value and leading to the highest-ever\npower conversion efficiency (PCE) reported for an <i>n-i-p</i> device with a sputtered NiO HTL. Employing optical and impedance\nspectroscopies, we investigate the mechanism of this self-healing\nprocess, establishing the dynamics of the process to be thermally\ncontrolled and independent of the storage ambient, indicating the\ndiffusion of the ionic species from the bulk to the interface as the\ndriving force for the recovery.