Keeping Chloride in Its Place for Efficient Perovskite Solar Cells

ABSTRACT

The efficiency and stability of perovskite solar cells remain constrained by the redistribution of mobile halide ions during film formation and operation. In the highlighted work, potassium binoxalate releases K ⁺ during annealing to associate with mobile Cl ⁻ and promote stable KCl formation, thereby suppressing interfacial chloride accumulation and producing a homogenized vertical chlorine distribution (HVCD). The resulting spatially uniform absorber exhibits reduced trap densities, improved energy‐level alignment, more efficient charge extraction, a certified steady‐state power conversion efficiency of 27.2%, and substantially improved operational stability. Beyond reporting a record device, the work establishes spatial ion management as a general design principle: additive‐derived ions must be controlled not only by chemical identity and concentration but also by their mobility and final position. This comment discusses the chemical basis, multiscale evidence, device implications, and potential extension of the strategy to bromide‐containing wide‐bandgap and tandem perovskites.