Synthesis of copper halide nanocrystals and their optical properties

Abstract

In the recent years, lead halide nanocrystals have received extensive research attentions as promising materials in optoelectronics applications due to their excellent light emitting properties including high photoluminescence quantum yield (PLQY), narrow full-width- at- half-maximum, and wide color gamut. However, toxicity is still major concern resulting in the pursuit of harmless lead-free structure development. Among the multifarious structures, copper-based halide nanocrystal is one of the most attractive due to high exciton binding energy leading to high PLQY of this family. In this report, we proposed the protocol for obtaining rubidium copper chloride nanocrystal using ligand- assisted reprecipitation (LARP) together with cooling process. The reprecipitation of cations (Rb+ and Cu+) with anion (Cl- ) were occurred in the presence of oleic acid ligand while the solution was cooled down from temperature at 135ºC to room temperature. We gradually observed cloudy solution within 10 min. The precipitation was purified with isopropanol for several times before further characterization. We found spherical nanoparticles under the transmission electron microscope (TEM), with 6.16 ± 1.2 nm in diameter. Although the X-Ray diffraction reveals two major structures including rubidium copper chloride (Rb2CuCl3) and rubidium copper chloride hydrate (Rb2CuCl4·2H2O), this colloidal nanocrystal still exhibits extremely bright photoluminescence emission peak at 392 and 398 nm under 286 nm excitation. Our finding demonstrates the next-generation light emitting material of rubidium copper chloride in term of low toxicity and bright emission