Efficient near-infrared down-conversion with potential applications in silicon solar cells and energy transfer mechanism from Eu2+ to Yb3+ in Ba5Si2O6Cl6

An efficient near-infrared down-conversion material, Eu 2+ -Yb 3+ co-doped Ba 5 Si 2 O 6 Cl 6 , was synthesized using a conventional high-temperature solid-state method. It can convert photons of 210–500 nm, which have a low spectral response of silicon solar cells , into visible and near-infrared light that can be efficiently utilized. Under 355 nm excitation, Ba 5 Si 2 O 6 Cl 6 :0.1Eu 2+ ,0.4Yb 3+ with optimal doping concentration shows strong near-infrared emission, and the main peak at 974 nm matches well with the spectral response of silicon solar cells . The existence of energy transfer (ET) from Eu 2+ to Yb 3+ was demonstrated using fluorescence spectra and fluorescence decay curves, and the energy transfer efficiency (ETE) was 64.58 % when the doping amount of Yb 3+ was 10 mol%. In addition, the quantum yield (QY) of Ba 5 Si 2 O 6 Cl 6 :Eu 2+ at the optimum excitation wavelength was as high as 88.52 %, and the temperature-dependent emission spectra indicated its outstanding thermal stability. Finally, the ET mechanism between Eu 2+ and Yb 3+ was systematically analyzed. The results indicate that the ET from Eu 2+ to Yb 3+ is a single-photon emission process with a single-step ET rather than a two-photon process. The above results show that the materials are down-conversion phosphors with broadband absorption efficient near-infrared emission, which are expected to be employed as spectral conversion materials for enhancing the efficiency of silicon solar cells.