Ultra-stable, Solution-Processable CsPbBr₃-SiO₂ Nanospheres for Highly Efficient Color Conversion in Micro Light-Emitting Diodes

Micro light-emitting diodes (μ-LEDs) coupled to color conversion phosphors are among the most promising technologies for future display and artificial light sources. However, current emitters suffer from excessively large particle sizes, preventing micron-scale processability, and/or low stability that hampers the device lifetime. Here, we demonstrate down-conversion μ-LED phosphors based on CsPbBr3 perovskite nanocrystals directly grown inside perfectly sealed mesoporous silica nanospheres (NSs). Key for this advancement is a high-throughput calcination procedure in the presence of K2CO3 as selective pore sealing agent, which simultaneously produces the CsPbBr3 nanocrystals, boosts their emission efficiency to >87%, and perfectly isolates them from the outer environment without causing inter-particle cross-linking or aggregation. This results in size-homogeneous, finely solution-dispersible, ultra-stable, and highly emissive CsPbBr3-SiO2 NSs that fit the technological requirements of photolithographic inks for highly uniform μ-LED color conversion patterns with pixels smaller than 20 μm.