Cesium Lead Iodide (CsPbI ₃ ): Progress, Challenges, and Prospects for Multifunctional Energy Conversion

ABSTRACT Cesium lead iodide (CsPbI 3 ), an all‐inorganic perovskite, has shown great promise for next‐generation energy conversion technologies because of its excellent optoelectronic characteristics, thermal stability, and adjustable band structure. With a direct bandgap of around 1.73 eV in its cubic α‐phase, CsPbI 3 is well‐suited for effective perovskite solar conversions (PSC's) with power conversion efficiencies higher than 20% when paired with surface passivation and proper film engineering. Applications in single‐junction and tandem photovoltaic (PV) designs have been made easier by the addition of perovskite quantum dots (QDs), which have better photostability, charge transport, and quantum confinement effects, owing to its low thermal conductivity and adjustable electrical characteristics, CsPbI 3 has shown promise in thermoelectric (TE) applications in addition to PVs, providing a route for hybrid energy harvesting. However, CsPbI 3 ’s phase instability, specifically, the spontaneous conversion of the black cubic α‐phase to the yellow non‐perovskite δ‐phase at ambient conditions, remains a barrier to commercialization. Its structural and environmental stability has been greatly enhanced by recent techniques, such as strain modulation, ligand engineering, doping, and nanostructuring. This review examines the most recent achievements in CsPbI 3 research, spanning its performance in PVs, QD‐based systems, TEs, and attempts to improve its long‐term stability. The report outlines future research routes to address current problems and maximize the potential of CsPbI 3 in multifunctional energy systems.