Computer model of amorphous silicon solar cell

Abstract

A computer model to simulate a n+ip+ amorphous silicon solar cell was developed. This model is based on the computer simulations of solar cells by T. Chappell and the Read diode by Scharfetter and Gummel. The model is used to generate field plots, band diagrams, quantum efficiency curves, I-V characteristics, carrier density distribution plots, carrier generation, and carrier recombination plots. The simulated values of short circuit current density, open circuit voltage, fill factor, efficiency, junction quality factor, quantum efficiency, junction quality factor, quantum efficiency, slope of I-V curves at V = 0 and V = Voc are in good agreement with the measured cell values. Computer simulation shows that a major loss mechanism is the back diffusion of holes into the n+ layer which is diminished by a strong electric field provided by a high concentration of ionized donors in the n+ layer. Projection of cell performance based on the production of n+ and p+ contact layers with ionized donor and ionized acceptor concentrations in the 2×1020 cm−3 range indicates cell efficiencies greater than 10%.