Tuning Perovskite Nanocrystal Synthesis via Amphiphilic Block Copolymer Templates and Solvent Interactions

High Resolution Image Download MS PowerPoint Slide Amphiphilic block copolymer (a-BCP) micelles offer morphological diversity and dimensional tunability, making them suitable for the fabrication of perovskite nanocrystals. However, precise control over the nucleation and growth of perovskite nanocrystals using a-BCP colloidal templates remains underexplored. This study investigates the effects of toluene, methanol, and polystyrene- block -poly(2-vinylpyridine) (PS- b -P2VP) on the formation of cesium lead bromide (CsPbBr 3 ) nanocrystals. The process involves four stages: (i) PS- b -P2VP micellization, (ii) PbBr 2 complexation, (iii) coordination interaction with P2VP, and (iv) burst nucleation of CsPbBr 3 nanocrystals. Toluene, a good solvent for PS but a nonsolvent for P2VP, PbBr 2, and CsBr, facilitates the formation of PS- b -P2VP spherical micelles. Adding PbBr 2 to these micelles in toluene results in multiple emulsion, dispersing PbBr 2 microstructures (microemulsion) and forming PbBr 3 − complexes encapsulated by the micelles (nanoemulsion). Prolonged stirring enhances this nanoemulsion. CsBr, insoluble in toluene, must be dissolved in methanol before being mixed with micelle-encapsulated complexes, promoting quick crystal nucleation. However, excess methanol weakens micellization, leading to the formation of fused micelles and irregular nanocrystals. At a high methanol content, PbBr 4 2– complexes also form, driving CsPbBr 3 to CsPb 2 Br 5 transformation via Ostwald ripening, resulting in large CsPb 2 Br 5 microcrystals that precipitate due to gravitational forces overcoming Brownian motion, destabilizing their dispersion in the solution.