A dual-mode solar spectral converter CaLaGa3S6O:Ce3+,Pr3+: UV-Vis-NIR luminescence properties and solar spectral converting mechanism

Abstract

A promising dual-mode solar spectral converter CaLaGa₃S₆O:Ce³⁺,Pr³⁺ for Si solar cells has been successfully developed. The structure, photoluminescence excitation and emission spectra in the UV-Vis-NIR region, and the decay curves have been systematically investigated. The results show that CaLaGa₃S₆O:Ce³⁺,Pr³⁺ exhibits two distinct solar spectral converting behaviors, quantum cutting (QC) (³P_J = 0,1,2 → ¹G₄ → ³H₄) and downshift (DS) processes (¹D₂ → ³F_J = 3,4), depending on different excited levels of Pr³⁺ and Ce³⁺. It can almost harvest UV-blue-red (250–625 nm) photons, greatly enhancing the utilization of solar spectrum especially in UV-Vis spectrum region, and convert into an intense broad NIR emission (930–1060 nm), perfectly matching the maximum spectral response of Si solar cells. We demonstrate that Ce³⁺/Pr³⁺ ions can form an efficient donor–acceptor pair, with high potential as full spectrum solar converter for Si solar cells, and Ce³⁺ ion can be an efficient sensitizer for harvesting UV photon and greatly enhancing the NIR emission of Pr³⁺ ion through efficient energy feeding by allowed 4f–5d absorption of Ce³⁺ ion with high oscillator strength. The NIR integrated emission intensity of CaLaGa₃S₆O:Ce³⁺,Pr³⁺ is 7.78 times as intense as that of a NIR quantum cutting phosphor Ca₂BO₃Cl:Ce³⁺,Tb³⁺,Yb³⁺ (CBC). We believe this new dual-mode solar spectral converter may open a new route to the design of advanced UV-Vis–NIR phosphors for Si based solar cell applications.