Sm³⁺-doped alkaline earth borate glasses as UV→visible photon conversion layer for solar cells

Intense multi-peak red fluorescence emissions of Sm³⁺ are exhibited in alkaline-earth borate (LKZBSB) glasses under UV radiation. The spontaneous emission probabilities A_rad corresponding to the ⁴G_5/2→⁶H_J (J=5/2, 7/2, 9/2 and 11/2) transitions are derived to be 24.74, 129.72, 117.03 and 32.23 s^-1, respectively, and the relevant stimulated emission cross-sections σ_em are 0.77×10^-22, 4.46×10^-22, 5.05×10^-22 and 1.38×10^-22 cm², confirming the effectiveness of red luminescence in Sm³⁺-doped LKZBSB glasses. Quantitative characterization through the evaluation of absolute spectral parameters reveals that the quantum yield of Sm³⁺-doped LKZBSB glasses is as high as 13.29%. Furthermore, with the introduction of Ce³⁺, the effective excitation wavelength range and the emission intensity of Sm³⁺ in LKZBSB glasses are remarkably expanded and improved by a maximum sensitization factor of 9.02 in the UVB region. These results demonstrate that the present glass system has promising potential as an efficient UV→visible photon conversion layer for the enhancement of solar cell efficiency, including appealing applications in outer space.