Spinel-Type Structured Phosphor Near-Infrared-II Emission: Intervalence Charge Transfer and Hetero-Valent Chromium Pairs

Near-infrared (NIR) emitting phosphors draw much attention because they show great applicability and development prospects in many fields. Herein, a series of inverse spinel-type structured LiGa5O8 phosphors with a high concentration of Cr3+ activators is reported with a dual emission band covering NIR-I and II regions. Except for strong ionic exchange interactions such as Cr3+−Cr3+ and Cr3+ clusters, an intervalence charge transfer (IVCT) process between aggregated Cr ion pairs is proposed as the mechanism for the ~1210 nm NIR-II emission. Comprehensive luminescence characterization points to IVCT between two Cr3+ being induced by structural distortion and further enhanced by irradiation. Therefore, this work provides insight into the emission mechanism within the high Cr3+ concentration system, revealing a new design strategy for NIR-II emitting phosphors to promote its response.
That dataset provides the raw data of room-temperature excitation and emission spectra and decay profiles, temperature-dependent photoluminescence and decay profiles, and high-pressure-dependent photoluminescence of LiGa5−xO8: xCr3+ (x=0.04–0.30).