Tailoring UV-blue sensitization effect in enhancing near infrared emission in X, Yb 3+ : CaGa 2 O 4 (X = 0, Eu 3+ , Bi 3+ , Cr 3+ ) phosphor for solar energy conversion

Abstract This work presents a strategy to modify the UV–vis part of solar spectrum into near infrared (NIR) region- an operational region for silicon solar cells. CaGa2O4, a wide band gap material, has been doped with Yb3+ ion and different sensitizers (Bi3+, Eu3+ and Cr3+) in order to probe the NIR emitting properties through downconversion (DC) process. Of these, Cr3+ ion serves the purpose of maximum conversion efficiency in a best way owing to its wide excitation spectrum spanning over the entire UV-blue region. The mechanisms involved in obtained results are supported by the decay curve measurement and energy transfer studies. Further, germainum ion is also doped to get long afterglow Yb3+ ion emission. This doping develops deep-traps that can store excitation energy and transfer it cooperatively via DC to Yb3+ for a longer time. Thus, the material is a promising spectral converter for c-Si solar cells and other photochemical processes.