Glass ceramics for frequency conversion

This chapter discusses transparent glass ceramics activated by rare earth ions as frequency converters based on energy transfer. These materials, in either bulk or thin-film form, may be useful to improve the efficiency of solar cells, by reducing the spectral mismatch. After a brief presentation of transparent glass ceramics, the basics of frequency conversion mechanisms are summarized, and some specific examples, mainly based on glass ceramics fabricated by sol-gel route, are reported. Finally, the case of Tb3+/Yb3+ silica-hafnia downconverters is discussed in detail.