Spontaneous Radiation Amplification in a Microsphere‐Coupled CsPbBr₃ Perovskite Vertical Structure

Abstract Microsphere (MS) cavities hold great potential in nanophotonics due to their extraordinary optical properties. All‐inorganic trihalide perovskites with high environmental stability and easy‐for‐preparation have shown great promise for the next‐generation optoelectronic nanodevices. Unfortunately, the nonradiative recombination of exciton is inevitably aggravating the photoluminescence quantum yields (PLQYs). Here, a microsphere‐coupled CsPbBr₃ perovskite vertical structure is proposed for amplification of spontaneous radiation (SR) up to 190‐fold. The mechanisms of SR amplification by an MS cavity are completely revealed, for the first time, including Mie focusing (MF) for energy harvesting, directional antenna (DA) for emission convergence, and whispering‐gallery modes (WGMs) for regulation of exciton dynamics. The temperature‐dependent photoluminescence (PL) spectra clarify the contributions of WGMs for the boosting of SR decay and suppression of exciton–phonon interactions for giant PL enhancement. Furthermore, a straightforward approach is presented for a selective MS array capped on a perovskite microcrystal (PeMC) film as a vertical structure for patterned PL enhancement. The excitation‐power‐ and excitation‐observation‐angle‐dependent luminescence contrast inspire a novel anticounterfeiting strategy. The vertical architecture not only advances the understanding of microcavity‐based SR amplification from PeMCs, but also offers opportunities to facilitate the synergistic manipulation of optical fields and exciton–phonon interactions for developing high‐efficient optoelectronic devices.