Self-Healing Significantly Improves Performances of NiO Sputtered n-i-p Perovskite Solar Cells

Using radio frequency magnetron sputter deposition to apply metal oxide thin film as a hole transporting layer (HTL) onto a halide perovskite layer significantly compromises the device photovoltaic performance. Therefore, despite its economic advantages and scalability potential, this method is generally not favored. Herein, we identify the primary cause of this limitation as the loss of the organic moiety from the near-interface region during the sputter deposition of NiO onto the halide perovskite and the consequent generation of interfacial defects. Furthermore, we show that a self-healing process, without any external intervention, is able to significantly compensate for the adverse effects of the sputtering process, resulting in the device efficiency to 180–220% of its initial value and leading to the highest-ever power conversion efficiency (PCE) reported for an n-i-p device with a sputtered NiO HTL. Employing optical and impedance spectroscopies, we investigate the mechanism of this self-healing process, establishing the dynamics of the process to be thermally controlled and independent of the storage ambient, indicating the diffusion of the ionic species from the bulk to the interface as the driving force for the recovery.