Fig. 1. (a) Powder XRD pattern of Cs3Cu2I5. (b) Crystal structure of NaI and Cs3Cu2I5. (c) XPS survey spectrum of Cs3Cu2I5 SC. (d)–(f) High-resolution XPS spectra of Cu 2p, I 3d, and Cs 3d, respectively.

Fig. 2. Optical properties. (a) Optical absorption spectra and PL spectra of Cs3Cu2I5 single crystal. Inset: photograph of crystal irradiated by 266 nm UV light. (b) Time-resolved PL decay of Cs3Cu2I5 single crystal (310 nm laser excitation). (c) PL spectra excited with various power densities of 266 nm UV light. (d) Normalized temperature-dependent PL spectrum from 77 to 300 K. (e) Integrated PL intensity as a function of excited power density (266 nm). (f) FWHM of PL versus temperature from 85 to 295 K.

Fig. 3. (a) Theoretical calculated absorption spectra of Cs3Cu2I5, CsI, LaBr3, and NaI versus photon energy from 1 keV to 10 MeV. (b) X-ray excited luminescence (XEL) spectra of Cs3Cu2I5 as a function of X-ray dose rate. The excited X-ray uses X-ray tube with Ag target, operated at 45 kV. (c) XEL decay profile of Cs3Cu2I5. (d) Schematic diagram of a band model scintillation mechanism of Cs3Cu2I5. VB, valence band; CB, conduction band; STEB, self-trapped exciton (STE) band.

Fig. 4. (a) Pulse height spectra of 662 keV gamma-ray from C137s radiation source. (b) Relative light yield as a function of gamma-ray energy.

Fig. 5. (a) XEL spectra of Cs3Cu2I5 crystal after irradiation with different doses of gamma rays from C60o. (b) Relative output of bulk Cs3Cu2I5 crystal stored in air at room temperature for 30 days.