Angular confining cavities for photovoltaics

Using anidolic or nonimaging optics principles, we present a study of the role of light confinement, with special application to photovoltaics. In particular, we study how and to what extent the reflectance of an absorbing surface can be reduced. Also, we study how and to what extent the absorption of light in a volume can be increased. In both cases the use of light confining cavities is the key for these improvements. Cavities different from the Helmholtz sphere, but rather based in an angular-spatial limitation of the escaping beam, are presented as a key tool for practical designs.