Spray-Drying Polymer Encapsulation of CsPbBr₃ Perovskite Nanocrystals with Enhanced Photostability for LED Downconverters

Lead halide perovskite nanocrystals (LHP NCs) exhibit remarkable optical and optoelectronic properties but greatly suffer from poor stability in standard ambient and in-use conditions. These stability issues hinder their utilization in many technological applications and their integration within industrial processes. Herein, we report a polymeric nanoencapsulation method of these NCs based on a spray-drying process, with the aim of using them as light downconverting materials in LED devices. CsPbBr3 NCs were encapsulated in acrylate-based polymers to form NC/polymer nanocomposite beads, with an average diameter lower than 500 nm. Structural and optical characterizations demonstrated good preservation of the NC properties after spray drying despite quite harsh process conditions. Specific acrylate-based polymers were selected in order to match native surface ligands from our NCs. This was necessary to obtain an effective encapsulation within the beads. To evaluate the photostability of encapsulated NCs under in-use conditions, bare NCs and encapsulated NCs were deposited on the chip of a blue LED downconverter to compare their luminescence stability. We observed that under continuous blue photon excitation, the NC/polymer nanocomposite beads exhibit much better resistance to photobleaching compared to bare NCs.