Inverted All-Inorganic CsPbI₂Br Perovskite Solar Cells with Promoted Efficiency and Stability by Nickel Incorporation

All-inorganic CsPbI₂Br perovskite solar cell with an inverted architecture of indium-tin oxide/poly[3-(4-carboxylbutyl)thiophene]/ CsPbI₂Br/(6,6)-phenyl-C₆₁-butyric acid methyl ester/C60/bathocuproine/ Ag was fabricated. Together with the incorporation of nickel iodide, perovskite crystallinity and film morphology were promoted. Also, suppressed trap-state density in perovskite film was accomplished due to the passivation effect. Consequently, enhanced champion efficiency of 13.88% with V_OC of 1.141 V, J_SC of 16.02 mA/cm², and fill factor of 75.96% was delivered by the doped optimal device, compared with the efficiency of 11.97% of the reference device. Superior device stability was demonstrated for the optimal device both in ambient atmosphere and N₂-filled glovebox, without encapsulation. Moreover, improved light stability was also confirmed for optimal device by prolonged operation time, under continuous illumination of simulated solar spectrum. In addition, high-temperature annealing or sintering of interlayer was eliminated by utilizing solution-processed poly[3-(4-carboxylbutyl)thiophene]-CH₃NH₂ (P3CT-CH₃NH₂) as the hole-transport layer. This work provides an alternative inverted architecture and an effective ion-doping strategy for efficient and stable all-inorganic perovskite solar cells (PSCs), which would help promote the development of PSC technology.