Under CopyrightSchweizer, S.S.SchweizerHenke, B.B.HenkeAhrens, B.B.AhrensPaßlick, C.C.PaßlickMiclea, P.T.P.T.MicleaWenzel, J.J.WenzelReisacher, E.E.ReisacherPfeiffer, W.W.PfeifferJohnson, J.A.J.A.Johnson2022-03-1116.10.20122010https://publica.fraunhofer.de/handle/publica/36923510.1117/12.85394310.24406/publica-r-3692352-s2.0-77953753825Transparent glasses as up- or down-converters are attractive systems to increase the efficiency of solar cells. Er-doped fluorozirconate (FZ) glasses show an intense up-conversion upon excitation at 1540 nm. Transmission spectra show that the absorbance at 1540 nm grows linearly with the Er-doping level. In Eu-doped FZ glasses, which were additionally doped with chlorine ions, the growth of BaCl2 nanocrystals can be observed upon thermal annealing. For high annealing temperatures a phase change from hexagonal to orthorhombic phase BaCl2 can be seen. Upon excitation in the ultraviolet (UV) spectral range these glass ceramics emit an intense blue emission. A combination of a silicon solar cell and an Eu-doped FZ glass ceramic as a down-converting top layer shows an increase in the short circuit current in the UV spectral range compared to a solar cell without a down-converting top layer.en621620697conference paper