Down-Shifting in the YAM: Ce³⁺ + Yb³⁺ System for Solar Cells

In this work, we investigate Ce³⁺ to Yb³⁺ energy transfer in Y₄Al₂O₉ (YAM) for potential application in solar spectrum down-converting layers for photovoltaic devices. Photoluminescence properties set, of 10 samples, of the YAM host activated with Ce³⁺ and Yb³⁺ with varying concentrations are presented, and the Ce³⁺ to Yb³⁺ energy transfer is proven. Measurement of highly non-exponential luminescence decays of Ce³⁺ 5d band allowed for the calculation of maximal theoretical quantum efficiency, of the expected down-conversion process, equal to 123%. Measurements of Yb³⁺ emission intensity, in the function of excitation power, confirmed the predominantly single-photon downshifting character of Ce³⁺ to Yb³⁺ energy transfer. Favorable location of the Ce³⁺ 5d bands in YAM makes this system a great candidate for down-converting, and down-shifting, luminescent layers for photovoltaics.