Recombination losses in thin-film CdS/CdTe photovoltaic devices

The losses accompanying the photoelectric energy conversion in thin-film CdS/CdTe devices faricated on the SnO2/glass substrates are analyzed. The extent to which the incomplete collection of the photogenerated carriers is determined by recombination at the CdS/CdTe interface and in the depletion layer is shown. The former is investigated based on the continuity equation with account made for surface recombination and the latter — from the Hecht equation. A comparison of the computed results and the experimental data shows that, in general, both types of recombination losses are essential but can be practically eliminated with a choice of appropriate barrier structure and material parameters, primarily of the carrier lifetime and the concentration of uncompensated impurities.