Thin Film Deposition and Optical Properties of Cs-Cu-I System Via Mist Deposition with Various Precursor Compositions

Cu-based metal halides, such as Cs3Cu2I5 and CsCu2I3, are promising materials for light-emitting diodes, photodetectors, and scintillators because of their excellent optical properties, non toxicity, and high air stability. In this study, we deposited thin films of the Cs-Cu-I system using Mist deposition varying the precursor composition of CsI and CuI and investigated their optical properties. X-ray diffraction 2θ-ω revealed that the Cs-Cu-I system thin films deposited by Mist deposition showed peaks corresponding to Cs3Cu2I5 and CsCu2I3 phases, with both phases existing in the composition of the concentration of Cu higher than Cs. Energy Dispersive X-ray Spectroscopy measurements presented the decreasing of Cs concentration in thin films compared to the precursor solution. The Cs-Cu-I system thin films exhibited blue and yellow emissions under UV radiation, originating from Cs3Cu2I5 and CsCu2I3, respectively. Especially, by adjusting the composition properly, Cs3Cu2I5 thin films achieved a photoluminescence quantum yield of 92.4% in thin films. This study paves the way for the thin film deposition and the application of Cu-based metal halide. ©2024 The Society of Materials Science, Japan.