Diode (characteristics in state-of-the-art ZnO/CdS/Cu(In1-xGax)Se2 solar cells

We report a new state of the art in thin-film polyctystalline Cu(In, Ga)Se-2-based solar cells with the attainment of energy conversion efficiencies of 19.5 %. An analysis of the performance of Cu(InGa)Se-2 solar cells in terms of some absorber properties and other derived diode parameters is presented. The analysis reveals that the highest-performance cells can be associated with absorber bandgap values of similar to 144eV, resulting in devices with the lowest values of diode saturation current density (similar to 3 x 10(-8) mA/cm(2)) and diode quality factors in the range 1-30 < A < 1.35. The data presented also support arguments of a reduced space charge region recombination as the reason for the improvement in the performance of such devices. In addition, a discussion is presented regarding the dependence of performance on energy bandgap, with an emphasis on wide-bandgap Cu(In,Ga)Se-2 materials and views toward improving efficiency to > 20 % in thin-film polycrystalline Cu(InGa)Se-2 solar cells. Published in 2005 by John Wiley W Sons, Ltd.