Ting L. Chu

Thin film II–VI photovoltaics

With the exception of HgSe and HgTe, II–VI compounds are direct gap semiconductors with sharp optical absorption edge and large absorption coefficients at above bandgap wavelengths. Device quality polycrystalline films of II–VI compounds can be prepared from inexpensive raw materials by a number of low-cost methods. They are well-suited for thin film solar cells and provide an economically viable approach to the terrestrial utilization of solar energy. Thin film II–VI solar cells are usually of the heterojunction type consisting of a high bandgap window (or collector) and a lower bandgap absorber. The grain boundary effects in polycrystalline II–VI films are considerably less pronounced than those in III–V films and can be passivated, at least partially, by chemical treatment. The use of CdS, ZnO, ZnSe and Cd1 − xZnxS as the window and the use of CdTe and Cd1 − xZnxTe as the absorber are reviewed in this paper. The fabrication and characteristics of a number of the thin film solar cell structures are discussed with emphasis on the thin film CdSCdTe solar cell.