Near-infrared DC approach by Bi3+–Yb3+ co-doped YAG phosphor

Bi 3+ –Yb 3+ ion pair co-doped YAG phosphors were successfully synthesized using conventional solid state reaction method varying the concentration of Yb 3+ ions from 0.5 to 10 mol%. The optimum phosphors were characterized by powder X-ray diffraction (XRD), and surface morphology was studied with a scanning electronic microscope (SEM). The photoluminescence (PL) properties were studied with a spectrophotometers in near infrared (NIR) and ultraviolet visible (UV-Vis) regions. The synthesized phosphors can convert a photon of UV region (330 nm) into photons of NIR region (979 and 992 nm). The co-operative energy transfer (CET) was studied using a time decay curve and PL spectra. The theoretical value of quantum efficiency (QE) was calculated from steady time decay measurement, and the maximum efficiency approached up to 166.91 %. Hence, this phosphor could be used as a downconversion (DC) luminescent convertor in front of crystalline silicon solar cell (c-Si) panels to reduce heat loss due to spectral mismatch of the solar cells.