Co-operative downconversion luminescence in Tm3+/Yb3+ : SiO2-Al2O3-LiF-GdF3 glasses

Oxyfluoride aluminosilicate glasses in the composition of 50SiO(2)-20Al(2)O(3)-20LiF-10GdF(3)-0.5TmF(3)-xYbF(3) (x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25 and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis measurements, glass transition temperatures and onset crystallization temperatures have been evaluated and from them glass stability factors were calculated. Glass stabilities decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for all these glasses. In these glasses, an efficient near infrared quantum cutting with optimal quantum efficiency approaching 187% has been demonstrated, by exploring the co-operative downconversion mechanism from Tm3+ to Yb3+, with 467 nm (Tm3+ : H-3(6) -> (1)G(4)) excitation wavelength. These glasses are promising materials to achieve high efficiency silicon based solar cells by means of downconversion in the visible part of the solar spectrum.