Dual‐Additive Doping Enables the Efficiency of Underwater Perovskite Laser Power Converters Exceed 50%

While laser wireless power transfer (LWPT) technology possesses transformative potential for powering autonomous underwater vehicles, laser power converters (LPCs) based on conventional III–V materials experience significant efficiency losses in aquatic environments. As a superior alternative candidate, wide‐bandgap formamidinium lead bromide (FAPbBr 3 ) perovskite demonstrates considerable potential for achieving highly efficient LPCs. However, FAPbBr 3 is often susceptible to various bulk and interfacial defects due to its rapid and uncontrollable crystallization process, rendering the formation of uniform and dense α ‐phase perovskite films challenging. In this study, a dual‐additive strategy is introduced, wherein rubidium iodide (RbI) cooperates with methylammonium chloride (MACl) to facilitate the attainment of high‐quality FAPbBr 3 crystals. As a result, the RbI‐treated LPC achieves a champion power conversion efficiency of 54.03% under 70 mW cm −2 @ 532 nm laser irradiation. Moreover, the device exhibits significantly enhanced long‐term storage ( T 92 @ 25°C 1800 h) and thermal stability ( T 90 @ 80°C 500 h). This work provides valuable insights and foundational knowledge for the development of perovskite LPCs and their application in underwater LWPT systems.