Facile NH₄Br pre-deposition enables effective buried interface passivation yielding 25.46 % efficiency in perovskite solar cells

The two-step method facilitates perovskite crystallization by pre-generating PbI 2 crystal nuclei and exhibits superior repeatability. Nevertheless, the two-step fabrication process results in a perovskite layer with many grain boundaries and interfacial defects, which act as non-radiative recombination sites, significantly limiting the V OC . At the same time, the quality of the resulting film strongly relies on how effectively organic salts diffuse within the PbI₂ layer. Herein, through a pre-deposition strategy, A pre-deposited NH 4 Br layer at the SnO 2 /perovskite interface effectively modulated the growth behavior of perovskite crystals. This led to the formation of a vertically grown perovskite film, featuring an average grain size of 1.37 μm. The pre-deposited NH 4 Br not only effectively suppressed interface recombination by reducing defect densities and enhanced carrier extraction, but also effectively improved perovskite film crystallinity and reduced PbI 2 content. Furthermore, the pre-deposition strategy extended the average carrier lifetime to 2.3 μs. Finally, perovskite devices based on pre-deposited NH 4 Br layer achieved a power conversion efficiency of 25.46 % and exhibited negligible hysteresis and good stability. In a word, the early incorporation of NH 4 Br at the SnO 2 /perovskite interface provides an effective approach to improving interfacial contact and reducing recombination, thereby enhancing device efficiency and long-term operational stability.