An efficient light converter YAB:Cr3+,Yb3+/Nd3+ with broadband excitation and strong NIR emission for harvesting c-Si-based solar cells

Abstract

Highly efficient Cr³⁺- and Yb³⁺/Nd³⁺-co-activated YAl₃(BO₃)₄ (YAB) phosphors have been developed as spectral convertors for improving silicon solar cell photovoltaic conversion efficiency. In the YAB lattice, Cr³⁺ ions act as broadband spectral sensitizers by absorbing UV-Vis (370–750 nm) photons, which are not absorbed by the silicon solar cell. After energy transfer, the Yb³⁺ acceptors then exhibit strong NIR emission centered at around 1000 nm, which is coupled well with the absorption band of the silicon solar cell. Efficient energy transfer is reflected by a sharp decrease in the excited state lifetime and red photoluminescence (PL) from Cr³⁺ with increasing Yb³⁺ concentration. Further evidence in favor of energy transfer is that PL-excitation spectra of NIR luminescence from Yb³⁺ are identical to those of deep red emission from Cr³⁺. Trivalent ions Gd³⁺, Bi³⁺ and La³⁺ have been introduced into YAl₃(BO₃)₄:Cr³⁺,Yb³⁺ in this study for a stronger NIR PL intensity. Additionally, energy transfer from Cr³⁺ to Nd³⁺ is also observed. Yb³⁺,Nd³⁺-co-activated YAB shows much broader NIR emission. Due to the effective absorption of Cr³⁺ in the visible region in YAB and the efficient energy transfer to Yb³⁺/Nd³⁺, these materials can be developed as spectral convertors to improve silicon solar cell photovoltaic conversion efficiency.