Minority carrier lifetime degradation in Si concentrator

A simple variation of the open-circuit voltage decay method of lifetime measurement was used to measure the dependence of minority carrier lifetimes in silicon concentrator cells upon the intensity of incident light. Effective lifetimes at intensity levels of up to 500 suns obtained by concentrating natural sunlight were measured. These measurements were performed on cells of different resistivities and base widths. It is found that the effective lifetime drops monotonically with increasing background illumination, particularly in high-resistivity cells. The degradation in effective lifetime is attributed to increased emitter recombination at high injection levels. A simple theoretical model that adequately accounts for this lifetime degradation was developed.