Luminescent properties and energy transfer of novel NIR K(Ga/Al)11O17:Cr3+,Yb3+ phosphors for solar cells

Novel Cr3+–Yb3+ codoped KGa11O17 and KAl11O17 phosphors (referred to as KGO:Cr3+,Yb3+ and KAO:Cr3+,Yb3+) were prepared via a traditional solid-state method. X-ray diffraction, scanning electron microscope equipped with an energy-dispersive spectrometer, and photoluminescence spectra were used to characterize the phase purity, chemical composition, and luminescence properties of the phosphors. The obtained KGO:Cr3+ and KAO:Cr3+ phosphors have high efficiency and broad absorption in the ultraviolet and visible (UV–vis) region. Under 300/420 nm excitation, KGO:Cr3+ and KAO:Cr3+ phosphors show deep red emission at about 712 nm. When Cr3+–Yb3+ are codoped into the KGO:Cr3+/KAO:Cr3+ matrix, the effective energy transfer from the Cr3+ to Yb3+ ions occurs, thus achieving intense near-infrared (NIR) emission. As a consequence, the high-energy UV–vis light can be efficiently converted into low-energy NIR light in KGO:Cr3+,Yb3+/KAO:Cr3+,Yb3+ phosphors based on the energy transfer process of the Cr3+→Yb3+ ions, which matches well with the high spectral response region of crystalline silicon (c-Si) solar cells. The experimental results reveal that KGO:Cr3+,Yb3+and KAO:Cr3+,Yb3+ phosphors are promising solar spectral conversion materials for c-Si solar cells.