The physics of solar cells

The photovoltaic mechanism is analyzed with special attention to the boundary conditions between emitter and junction. In frontwall cells, these boundary conditions are rather simple and permit a transparent analysis. They connect the current, determined by the emitter/junction boundary, with the potential drop in the junction, determined by the same condition, and yield the current-voltage characteristic without invoking the superposition principle. The chemistry of the interlayer between the emitter and the junction may modify this characteristic when causing major interface recombination, resulting in a potential deformation. Such behavior is analyzed in more detail for the example of CdS/Cu2S and CdzZn1−zS/Cu2S solar cells. Substantially improved agreement between the results of this theory and experiment is reached.