Silica Surface Coating of Blue Light-Emitting CsPbBr₃ Nanoplatelets for Improved Stability in Polar Solvents and Long-Term Storage

Colloidal quantum-confined perovskite CsPbBr 3 nanoplatelets (NPLs) exhibit blue emission, making them promising for blue LEDs. It is known that the thickness of CsPbBr 3 NPLs is not stable especially in polar solvents and during long-term storage, causing their absorption and emission to red-shift due to the transformation to a larger structure. To cope with this limitation, we developed a surface coating method to protect the NPLs. In particular, we designed a system to stabilize the thickness of NPLs during the silica coating process. We also explored the impact of functional groups of the capping ligands and reaction time on the spectroscopic performance of the NPLs to gain some insights into the surface passivation mechanism, which will benefit future shell growth methods using other materials, not only limited to silica. Under the optimal reaction conditions, a photoluminescence quantum yield of 81% was achieved for the silica coated CsPbBr 3 NPLs. These NPLs exhibited good stability in water and other polar solvents and after long-term storage. Density functional theory calculations show that the binding affinity of water on the NPL is decreased by silica coating. Based on the findings in this study, we proposed a mechanism of how a coating formed on the NPL surface to improve the stability and enhance the performance of CsPbBr 3 NPLs.