Stabilizing the Chemistry of NiOx in Perovskite Solar Cells to Pass the Damp Heat Test

NiOx is widely used as a hole transport material in perovskite solar cells (PSCs). This wide band gap p-type material is conveniently deposited via high throughput RF-sputtering, making it suitable for the industrialization of PSCs. Nonetheless, for the cells to pass accelerated degradation tests such as the IEC 61215 damp heat (DH) test, the chemistry of the NiOx film should remain constant at elevated temperaturs to preserve its optoelectronic properties. This study emphasizes that structural defects resulting from Ni vacancies in NiOx lead to significant degradation of the PSCs after just a few hours of exposure to elevated temperatures (85 °C). We introduce here an approach to fine-tune the chemistry of the NiOx film by adjusting the gas flow during sputtering deposition and by incorporating Cs. Through this control on the chemistry of the layer, the optimized NiOx-based PSCs exhibit remarkable stability, with devices passing 5 times the IEC 61215 norm (