Problems of efficiency of photoelectric conversion in thin-film CdS/CdTe solar cells

The available data are generalized and new results of investigation of losses of photoelectric energy conversion in CdS/CdTe thin-film solar cells are reported. The requirements concerning the electrical characteristics of the material, for minimizing the electric losses and providing effective radiation absorption in the active region of the diode structure, are discussed and refined. It is shown to what extent the incomplete collection of photogenerated charge carriers is determined by recombination both at the CdS/CdTe interface (based on the continuity equation taking into account the surface recombination) and in the space-charge region (based on the Hecht equation). The comparison of the calculated and experimental results shows that, in general, both types of recombination losses are important but can be virtually eliminated by the choice of parameters of both the barrier structure and the material used. The limiting values of the short-circuit current density and efficiency of the CdS/CdTe solar cell are discussed.