Visible to near-infrared downconversion in Tm3+/Yb3+ co-doped chalcohalide glasses for solar spectra converter

Near-infrared downconversion which can be used to improve the utilization of solar spectral has drawn much attention. In this work, chalcohalide glasses with compositions of 50GeS2-25Ga2S3-25CsCl (in mol.%): 0.1 wt.% Tm2 S3 - x wt.% Yb2S3 (x = 0, 0.1, 0.2, 0.3) were synthesized by vacuumed melt-quenching method. Absorption spectra, emission spectra, excitation spectra, and decay measurements were performed to prove the occurrence of cooperative energy transfer from the 1G4 level of Tm3+ ions to two Yb3+ ions. Quantum efficiency depends on Yb3+ concentration is calculated, and the highest is 114.1%. The photon energy of Yb3+ emission around 1 µm well matched with the operation band gap of the crystalline Si, so the glasses could potentially be applied in Si-based solar cell.