Cesium Copper Iodide Tailored Nanoplates and Nanorods for Blue, Yellow, and White Emission

Inorganic metal halide perovskite nanocrystals (NCs) are promising materials for emission-based applications; however, the inclusion of toxic lead may limit their commercial viability. This paper describes two cesium cupriferous iodides as nontoxic alternatives to lead containing perovskites. These nanocrystals were synthesized with tailored composition and morphology by a hot-injection colloidal route to produce hexagonal nanoplates (NPs) of blue-emitting Cs3Cu2I5 and nanorods (NRs) of yellow-emitting CsCu2I3. Phase purity was confirmed by Rietveld refinement of X-ray powder diffraction patterns and solid state 133Cs MAS NMR with both compounds exhibiting high thermal stability suitable for optoelectronic technologies. Phase mixing allows linear tuning of Commission Internationale de l’Eclairage (CIE) coordinates from (0.145, 0.055) to (0.418, 0.541) such that a 1:8 molar ratio of Cs3Cu2I5 NPs and CsCu2I3 NRs yields white emission, while the 133Cs MAS NMR demonstrates that these photophysical effects are not attributed to any changes in the Cu oxidation state.