Finite-Size Effects on Cs₃Cu₂I₅ 0D Electronic Nanostructures for Ultraviolet-Emitting Applications

The potential to produce ultraviolet (UV) light-emitting devices has attracted significant interest in interdisciplinary fields, particularly in the use of 0D halide nanostructures due to their straightforward synthesis methods and exceptional efficiency in optoelectronics. Here, we present a systematic study involving nanostructure synthesis and significant changes in the electronic structure caused by finite-size effects. We have focused on the investigation of size effects on the UV-light emitting properties of all-inorganic Cs 3 Cu 2 I 5 halide. We observe that bulk particles present a pronounced bright-blue emission at 440 nm with a high quantum yield of 80%. Very small quantum dots nanostructures (6–10 nm) reveal a significant shift of the photoluminescence peak down to ∼395 nm, close to the UV-A region, but with a quantum yield reduction of 10%. Surface engineering to obtain very small nanoparticles free from defects at the nanocrystal surface is crucial for maintaining a high quantum efficiency, allowing their use in UV-emitting devices.