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Cr,Yb-codoped Ca2LaHf2Al3O12 garnet phosphor: electronic structure, broadband NIR emission and energy transfer properties.

Dayu HuangQiuyun OuyangHui XiaoBo WangHongzhou LianQingguang ZengJun Lin
Published in: Dalton transactions (Cambridge, England : 2003) (2020)
The combination of a broadband near-infrared (NIR) phosphor and phosphor-converted light-emitting diodes (pc-LEDs) has proven to be an ideal choice for a high-efficiency NIR light source. Here, a garnet-type NIR Ca2LaHf2Al3O12:Cr3+ phosphor is obtained and its emission covered most of the NIR spectral range. Excited by 460 nm blue light, the maximum peak was located at 780 nm with a full width at half maximum (FWHM) of ∼141 nm and an internal quantum efficiency (IQE) of 33%. Moreover, the NIR spectra can be broadened by doping Yb3+ into the Ca2LaHf2Al3O12:Cr3+ garnet phosphor. A super broad FWHM of 300 nm and reduced thermal quenching were acquired, originating from the energy transfer of Cr3+→ Yb3+. The energy transfer process of Cr3+ and Yb3+ is described by means of an energy level diagram and time-resolved spectrum. Finally, a NIR pc-LED is fabricated by combining the Ca2LaHf2Al3O12:Cr3+,Yb3+ phosphor with blue chips, which has a photoelectric conversion efficiency of 10%. These results demonstrate the great potential of Ca2LaHf2Al3O12:Cr3+,Yb3+ in super broadband NIR pc-LED applications.
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