Improved theory of the silicon p-n junction solar cell

The theory of the silicon p-n junction solar cell in its present state is inadequate to explain the observed fall-off in power output and open-circuit voltage with increasing substrate doping. The present work removes this deficiency by incorporating into the theory the generation-recombination dark current in the junction appropriately corrected for the thermal counterpart of the Franz-Keldysh effect. The light generated short-circuit current is calculated from the known solar spectrum and band gap and from estimates of reflection, absorption, obstruction, transmission, and recombination losses. The improved theory permits a detailed quantitative explanation of the experimentally measured current-voltage characteristics of conventional, violet, and nonreflective silicon solar cells for beginning-of-life and end-of-life performance in a space environment and as a function of thickness. It also explains the temperature coefficient of the short-circuit current, of the open-circuit voltage, and of the power output of these three types of cell. Finally, the theory explains the observed fall-off in power output and open-circuit voltage with increasing substrate doping and predicts the maximum efficiency to be expected in state-of-the-art material for optimized cell thickness and doping for both beginning-of-life and end-of-life situations. 34 references.