Effectively realizing broadband spectral conversion of UV/visible to near-infrared emission in (Na,K)Mg(La,Gd)TeO:Mn,Nd,Yb materials for c-Si solar cells: Via efficient energy transfer

In this work, a series of (Na,K)Mg(La,Gd)TeO:Mn,Nd,Yb materials were prepared via a high-temperature solid-state reaction method. As reported before, certain Mn singly doped samples present good red luminescence properties, showing emission bands at around 700 nm upon excitation with UV/n-UV/blue light. When Mn and Nd were co-doped into the same host, effective energy transfer from Mn to Nd ions was inferred from the spectral overlap of the Mn emission and Nd excitation bands. The variation of the emission bands upon 365 nm UV excitation with fixed Mn concentration and varying Nd concentration in phosphors can validate this energy transfer process from Mn to Nd ions. In addition, comparison of the excitation spectra monitored at the Nd emission peaks to those monitored at the Mn emission bands and the decrease of the Mn decay times supplied more evidence for the energy transfer phenomenon from Mn to Nd ions in these Mn,Nd co-doped samples. Since the energy transfer from Nd to Yb ions has been well reported before, we co-doped Yb in our Mn,Nd co-doped samples to show that Nd can be a bridging ion to regulate the energy transfer from Mn to Yb ions for the first time, which was confirmed from the analysis of the excitation spectra and decay times. This can be considered as a novel method to enhance the energy transfer from Mn to Yb ions. Based on the energy transfer from Mn to Nd and then to Yb, UV/visible luminescence can be effectively converted into near-infrared emission, allowing a better spectral response for c-Si solar cells, which suggests a possible enhancement of the conversion efficiency of such c-Si solar cells.