Efficient Near-Infrared Quantum Cutting in Tm3+/Yb3+ Codoped LiYF4 Single Crystals for Solar Photovoltaic

Abstract

Downconversion (DC) with emission of two near-infrared photons about 1000 nm for each blue photon absorbed was obtained in thulium (Tm3+) and ytterbium (Yb3+) codoped yttrium lithium fluoride (LiYF4) single crystals grown by an improved Bridgman method. The luminescent properties of the crystals were measured through photoluminescence excitation, emission spectra and decay curves. Luminescence between 960 and 1050 nm from Yb3+: 2F5/2→2F7/2 transition, which was originated from the DC from Tm3+ ions to Yb3+ ions, was observed under the excitation of blue photon at 465 nm. Moreover, the energy transfer processes were studied based on the Inokuti-Hirayama model, and the results indicated that the energy transfer from Tm3+ to Yb3+ was an electric dipole-dipole interaction. The maximum quantum cutting efficiency approached up to 167.5% in LiYF4 single crystal codoped with 0.49mol% Tm3+ and 5.99mol% Yb3+. Application of this crystal has prospects for increasing the energy efficiency of crystalline Si solar cells by photon doubling of the high energy part of the solar spectrum.