Phase Control and Singlet Energy Transfer Enabled by Trimethylamine Modified Boron Dipyrromethene for Stable CsPbBr3 Quantum Wells

Abstract The phase distribution and organic spacer cations play pivotal roles in determining the emission performance and stability of perovskite quantum wells (QWs). Here, we propose a universal molecular regulation strategy to tailor phase distribution and enhance the stability of CsPbBr 3 QWs. The capability of sterically hindered ligands with formidable surface binding groups is underscored in directing CsPbBr 3 growth and refining phase distribution. With trimethylamine modified boron dipyrromethene (BDP‐TMA) ligand as a representative, the BDP‐TMA driven can precisely control phase distribution and passivate defects of CsPbBr 3 . Notably, BDP‐TMA acts as a co‐spacer organic entity in obtained BDP‐TMA‐CsPbBr 3 , facilitating efficient singlet energy transfer and tailoring the luminescence to produce a distinctive bluish‐white emission. The BDP‐TMA‐CsPbBr 3 demonstrates significant phase stability under water exposure, light irradiation, and moderate temperature. Interestingly, BDP‐TMA‐CsPbBr 3 exhibits the thermally‐induced dynamic fluorescence control at elevated temperatures, which can be achieved feasible for advanced information encryption. This discovery paves the way for the exploration of perovskite QWs in applications like temperature sensing, anti‐counterfeiting, and other advanced optical smart technologies.