Single‐Photon Emission from Single Microplate MAPbI₃ Nanocrystals with Ultranarrow Photoluminescence Linewidths and Exciton Fine Structures

Abstract Stimulated by the superior performance of organic–inorganic MAPbI₃ perovskite films in photovoltaic devices, a lot of research interest is now being devoted to their low‐dimensional nanocrystals (NCs) to extend the optoelectronic functionalities as well as to promote the potential applications in quantum information technologies. Compared to other organic–inorganic and all‐inorganic counterparts that have been intensively studied, the MAPbI₃ NCs suffer from the optical and chemical instabilities so that their single‐particle photophysical properties have been largely unexplored up to now. Here, the authors have synthesized single MAPbI₃ microplates from a two‐step method and characterize their optical properties mainly at the cryogenic temperature, showing that localized optical emitters are universally present with the quantum feature of single‐photon emission. Photoluminescence (PL) linewidth measured for such a single quantum emitter can be as narrow as ≈200 μeV, as a direct consequence of its embedment inside the microplate with the spectral diffusion effect being greatly suppressed. This has allowed them to resolve the exciton fine structures from some of the studied single quantum emitters, each of which is manifested as a PL doublet with the energy separation of ≈600 μeV and the orthogonally linear polarizations.