Room Temperature Polariton Condensation from Whispering Gallery Modes in CsPbBr3 Microplatelets

Abstract Room temperature (RT) polariton condensate holds exceptional promise for revolutionizing various fields of science and technology, encompassing optoelectronics devices to quantum information processing. Using perovskite materials, like all‐inorganic cesium lead bromide (CsPbBr 3 ) single crystal, provides additional advantages, such as ease of synthesis, cost‐effectiveness, and compatibility with existing semiconductor technologies. In this work, the formation of whispering gallery modes (WGM) in CsPbBr 3 single crystals with controlled geometry is shown, synthesized using a low‐cost and efficient capillary bridge method. Through the implementation of microplatelets geometry, enhanced optical properties and performance are achieved due to the presence of sharp edges and a uniform surface, effectively avoiding non‐radiative scattering losses caused by defects. This allows not only to observe strong light matter coupling and formation of whispering gallery polaritons, but also to demonstrate the onset of polariton condensation at RT. This investigation not only contributes to the advancement of the knowledge concerning the exceptional optical properties of perovskite‐based polariton systems, but also unveils prospects for the exploration of WGM polariton condensation within the framework of a 3D perovskite‐based platform, working at RT. The unique characteristics of polariton condensate, including low excitation thresholds and ultrafast dynamics, open up unique opportunities for advancements in photonics and optoelectronics devices.