An improved conventional Se–CdO photovoltaic cell

Studies previously carried out to improve the Se–CdO photovoltaic cell have emphasized optimization of the deposition of the CdO by direct current (DC) reactive sputtering. Attention has now been turned towards improving the deposition, doping, and heat treatment of the polycrystalline selenium base. It has been found that heat treatment of the selenium film on its substrate of aluminum and bismuth in air or oxygen prior to CdO deposition results in an increase in the illuminated open-circuit voltage (Voc) of the cell. The effect increased with increase of annealing temperature from 150 to 195 °C and in going from dry to wet oxygen. No increase in Voc was found by heating in nitrogen. The effect could be due to the formation of higher stoichiometric and hence higher resistivity CdO at the Se–CdO junction, arising from the presence of extra oxygen on the selenium surface.