Evidence for generalized Kirchhoff's law from angle-resolved electroluminescence of high efficiency silicon solar cells

The angular distribution of infrared radiation, emitted by high efficiency single-crystalline silicon solar cells, was analyzed. Measurements were performed on cells with planar and inverted-pyramids surfaces, both showing integral emissions that approach the cosine function in the 0degrees-90degrees interval. Textured cell maintains the cosine distribution at the different wavelengths; planar device shows a distribution, which deviates from the cosine function at increasing wavelength. Correspondence between emission and absorption properties was demonstrated valid as a function of emission/absorption angle. From the angular distribution of electroluminescence light, the devices absorption properties for incident light with directions different from the surface normal were estimated. (C) American Institute of Physics.