Abstract
Metal halide perovskites show great potential for indoor photovoltaics, but their application is limited by significant nonradiative recombination under low‐intensity indoor light due to defects. In this work, alkali iodides are used as an effective passivator to simultaneously mitigate defects at the buried interface, bulk lattice, and surface of the perovskite film. The alkali iodide promotes uniform morphology with large grains and phase stability. Specifically, the diffusion of rubidium iodide (RbI) into perovskite suppresses defects at both the interfaces and the bulk of the perovskite film. Consequently, the optimum use of RbI improves power conversion efficiencies of perovskite solar cells (PSCs) from 20.08% to 21.53% under 1 SUN, and from 31.41% to 37.09% under 1000 lux light‐emitting diode (LED) illumination. Furthermore, the RbI‐treated devices maintain 90% of their initial efficiency after 1000 h under 1000 lux LED illumination without encapsulation, demonstrating excellent operational stability. Furthermore, self‐powered internet of things (IoT) sensors driven by RbI‐treated PSCs under indoor lighting are demonstrated, validating the practical viability of this approach. This work provides a comprehensive understanding of the role of alkali iodides in perovskite, and offers a viable pathway for developing highly efficient and stable indoor PSCs, paving the way for their integration into self‐powered IoT applications.