Broadband ultraviolet to near infrared conversion in Eu2+,Nd3+ co-doped SrAl2O4

Abstract

In this study, we investigated the quantum cutting (QC) mechanism in Eu²⁺–Nd³-co-doped SrAl₂O₄ microcrystals by fluorescence spectroscopy and decay lifetime analysis. In this material, the near-infrared (NIR) emissions of Nd³⁺ in the range of 800–1200 nm were enhanced under the excitation of the Eu²⁺:4f⁷ → 4f⁶5d¹ transition radiation. The lifetime of the 5d¹ level of Eu²⁺ decreased with the increase in the Nd³⁺ concentration. These results verified the occurrence of cooperative energy transfer (CET) from the Eu²⁺:5d¹ excited state to the Nd³⁺:⁴F_3/2 level, by which one absorbed ultraviolet-visible photon was converted to two NIR photons with an optimal quantum efficiency (QE) of approximately 177.1%. Therefore, this broadband QC material paves the way for a further increase in the conversion efficiency of c-Si solar cells.