Efficient NIR quantum cutting of Eu3+/Yb3+ co-doped LiLa(PO3)4 for luminescent solar concentrators

Abstract

An efficient near-infrared (NIR) quantum cutting (QC) process was provided from 5% Eu3+/Yb3+ co-doped LiLa(PO3)4 crystalline phosphor synthesized by solid reaction. The obtained phosphors are identified by X-ray diffraction, IR absorption spectroscopy, Raman scattering spectroscopy and SEM. The energy transfer from Eu3+ to Yb3+ ions in LiLa(PO3)4 was studied based on excitation and emission spectra as well as decay curves of the Eu3+ ion luminescence in mono-doped Eu3+ and co-doped Eu3+/Yb3+ phosphors. The emission intensity of Eu3+ decreases after co-doping with Yb3+. The conversion from the mono-exponential to bi-exponential shape of the decay curves as well as the drop in the lifetime of the Eu3+ emission in LiLa(PO3)4 after co-doping with Yb3+ prove the energy transfer from Eu3+ to Yb3+. The possible energy transfer mechanisms involved in different transitions are discussed and a schematic energy level diagrams was proposed. The quantum efficiency was calculated and estimated to be 168%. The obtained results revealed the importance of the NIR QC investigated in Eu3+/Yb3+ co-doped LiLa(PO3)4 for enhancing the photovoltaic conversion efficiency in c-Si solar cell through spectral modification.