Room-temperature Sputtered NiOx for hysteresis-free and stable inverted Cs-FA mixed-cation perovskite solar cells

In this research, a room-temperature sputtering technology for fabricating high performance NiOx film was developed, which was applicable for inverted cesium (Cs)-formamidinium (FA) mixed-cation perovskite solar cells (PSCs). The Ni3+/Ni2+ ratio in sputtered NiOx film was effectively adjusted by controlling Ar pressure while sputtering. NiOx films with appropriate Ni3+/Ni2+ ratio exhibit uniform surface morphology, high transmittance, and better energy level match with the perovskite layer. By using this sputtered NiOx film as hole transporting layer, short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF) and power conversion efficiency (PCE) of a champion inverted PSC were 19.25 mA/cm2, 1.05 V, 0.80 and 16.23%, respectively. Also, these devices remained 90.6% of their initial PCE after light soaking at a surrounding temperature of 50 °C for more than 600 h.