An intense charge transfer broadband sensitized near-infrared emitting CaLaGa3S6O:Yb3+ phosphor suitable for solar spectral convertor

A near-infrared (NIR) phosphor, CaLaGa3S6O:Yb3+, is developed as a promising solar spectral convertor for Si solar cells. The structure, photoluminescence excitation and emission spectra, concentration effect are investigated. The results show that CaLaGa3S6O: Yb3+ has an efficient broad absorption band dominating around the 345 nm ascribing to the charge transfer state (CTS) of Yb3+-S2- and exhibits an intense NIR emission of Yb3+ between 920 and 1150 nm, perfectly matching the maximum spectral response of Si solar cells. The NIR emission intensity of CaLaGa3S6O: Yb3+ is 12 times as intense as that of a NIR quantum cutting phosphor Ca2BO3Cl:Ce3+, Tb3+, Yb3+ (CBC) upon 4f-5d excitation of Ce3+. These results demonstrate that the allowed CTS of Yb3+-S2- with high absorption cross-section can be an efficient and direct sensitizer harvesting UV-blue photons and greatly enhancing the NIR emission of Yb3+ ion. (C) 2011 Optical Society of America