Synthesis of homogeneous and bright deep blue CsPbBr 3 perovskite nanoplatelets with solidified surface for optoelectronic material

Halide perovskite nanocrystals have easily tunable emissions throughout the visible spectrum, making them an extremely promising material for light‐emitting applications. Whereas high quantum yield and long‐term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind with low quantum yields and insufficient colloidal stability. In this study, we present a facile synthetic and postsynthetic approach for obtaining two‐dimensional CsPbBr 3 nanoplatelets (NPLs) with homogeneous‐thickness control of their solidified surface, resulting in sharp photoluminescence and electroluminescence peaks with a deep‐blue emission at 465‐nm wavelength owing to quantum confinement. The subsequent addition of a solidifying ligand solution seals the surface defects likely stemming from vacancies within a subensemble of weakly emissive NPLs. The overall photoluminescence quantum yield of the blue‐emissive colloidal dispersions is consequently enhanced by 65% ± 2%.