Highly efficient In(I) doped Cs3Cu2I5 single crystals for light-emitting diodes and gamma spectroscopy applications

High-quality Cs3Cu2I5:In single crystals with a 7 mm diameter were grown by using the vertical Bridgman method. These crystals have a high optical transmittance (>75 %) and emit a bright red-orange light under both UV and X-ray irradiation. The Cs3Cu2I5:In crystals can exhibit a high photoluminescence quantum efficiency (PLQY) of 79.5 %, thus we explored the potential applications for light-emitting diodes (LED). The fabricated LED demonstrated CIE color coordinates of (0.553, 0.431) with a color rendering index (Ra) of 77, making it suitable for supplementary light in plant growth. Moreover, we evaluated their gamma-ray spectroscopy capability by using an avalanche photodiode (APD) detector. Under 137Cs gamma-ray irradiation, the gamma scintillation yield and energy resolution gradually degraded as the In concentration increased, which can be attributed to an enhanced afterglow after In doping.