Abstract
Operational instability of perovskite solar cells is often attributed to ion migration, but the isolated impact of the electric field separate from light and heat remains poorly understood. Here, we screen perovskite absorbers and transport layers to identify compositions that withstand pure electric field stress. Using PL microscopy, IR s-SNOM, SEM/EDX, and ToF- SIMS, we systematically compare a range of compositions and unravel the dominant aging pathways under a bias field of 1 V/μm, comparable to fields experienced at the maximum power point. Among single-cation perovskites, MAPbI₃ degrades rapidly via cathodic reduction of methylammonium and anodic oxidation of iodide. FAPbI₃ also shows poor stability, with void formation and massive formamidinium loss. In contrast, the double-cation formulation Cs0.15FA0.85PbI₃ exhibits the highest stability, retaining most organic cations and preserving PL intensity. Replacing MA with FA cations clearly improves stability in the cathodic region, making iodide oxidation the primary degradation pathway. Interestingly, mixing three cations in Cs0.1MA0.15FA0.75PbI3 significantly stabilizes both MA and FA cations compared to their single-cation counterparts . However, these multication films still undergo field-induced phase segregation into MA-rich and FA-rich domains, though both polyiodide formation and phase segregation appear partially reversible . For hole transport layers, we find that PTAA-based systems (bare PTAA and binary NiOx/PTAA) outperform bare NiOx . The superior stability of PTAA arises from its chemical inertness toward the perovskite. In contrast, bare NiOx triggers severe degradation via interfacial chemical interactions, leading to almost complete depletion of organic cations from the active layer and their accumulation in the PC61BM electron transport layer, as revealed by ToF-SIMS. Finally, we show that for fullerene-based ETLs, the degradation rate directly correlates with film uniformity. PC₆₁BM ETLs deposited from chloroform exhibit high stability even after 1000 h under 1.2 V bias. In contrast, chlorobenzene-deposited films degrade severely. IR s-SNOM reveals PC61BM aggregation in chlorobenzene-cast films, which we identify as the primary cause of poor uniformity and defects formation . Overall, our results establish the critical role of both perovskite composition and transport layer selection in determining device stability under pure electric field stress, providing a clear roadmap for more robust perovskite solar cells.