INCREASING THE EFFICIENCY OF IDEAL SOLAR-CELLS BY PHOTON-INDUCED TRANSITIONS AT INTERMEDIATE LEVELS

Recent attempts have been made to increase the efficiency of solar cel ls by introducing an impurity level in the semiconductor band gap. We present an analysis of such a structure under ideal conditions. We pro ve that its efficiency ran exceed not only the Shockley and Queisser e fficiency for ideal solar cells but also that Tor ideal two-terminal t andem cells which use two semiconductors, as well as that predicted fo r ideal cells with quantum efficiency above one but less than two.