Dependences of the open-circuit voltage, short-circuit current, fill factor. and efficiency of a CdS/CdTe solar cell on the resistivity and thickness of the p-CdTe absorber layer. the noncompensated acceptor concentration N(a)-N(d), and carrier lifetime tau in CdTe, are investigated, and optimization of these parameters in order to improve the solar cell efficiency is performed. It has been shown that the observed low efficiency of CdS/CdTe solar cells is caused by the too short electron lifetime in the range of 10(-10)-10(-9) s and too thin (3-5 mu m) CdTe layer currently used for fabrication of CdTe/CdS solar cells. To achieve an efficiency of 28-30%, the resistivity and thickness of the CdTe absorber layer, the noncompensated acceptor concentration, and carrier lifetime should be similar to 0.1 Omega.cm, >= 20-30 mu m, >= 10(16) cm(-3), and >= 10(-6) s, respectively. (C) 2008 Elsevier B.V. All rights reserved.