Water-Soluble V₂O_5-x Enables Efficient Inverted Perovskite Solar Cells With High Operational and Reverse Bias Stability

Perovskite solar cells (PSCs) face challenges in long-term stability, especially under reverse bias. Here, a water-soluble vanadium pentoxide (V₂O_5-x) hole-collecting layer (HCL) is introduced into inverted PSCs to improve the photovoltaic performance and multiple-scenario stability under operational, thermal recycle, and reverse bias. V₂O_5-x annealed at 50–250°C are characterized for multiple physical properties, revealing that 150°C annealing optimizes oxygen vacancy to reduce trap density and improve interface carrier collection. The champion device based on (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.95Br_0.05)₃ absorber achieves power conversion efficiency (PCE) of 23.3% with negligible hysteresis (HI = 0.64%) and good stability (retains ∼88% of initial PCE after 1000 h of storage). Further, with Cs_0.05MA_0.1FA_0.85PbI₃ as absorber, the PCE of the device can be further improved to be 25.88% with an HI of 3.26%, superior to the device without V₂O_5-x (PCE = 24.94%, HI = 5.47%). Moreover, the operational and thermal cycling stability of the device has been obviously improved. Crucially, V₂O_5-x enhances the reverse breakdown voltage from about |−2| to |−6| V, endowing the device with higher reverse bias stability and tolerance to the shadow effect. These results demonstrate that V₂O_5-x can simultaneously boost PCE and stability of PSCs, offering a promising route toward efficient and durable PSCs.