Measurement of minority carrier lifetime of solar cells using surface voltage and current transients

Abstract

The voltage decay transients along the emitter surface of the p- n junction solar cell under forward current-induced and nonuniform illuminated cases have been studied experimentally. The open-circuit voltage decay transients in these cases have also been recorded. It is found that the surface voltage decays exponentially with time and is independent of depletion-region effects. The open-circuit voltage decay behaviour, under such situations, shows that the V oc initially increases with time, and after attaining a maximum value, decays usually. The initial increase, in both current- and photo-induced cases, is attributed to the surface voltage. The lifetime measured by surface voltage decay method is more accurate than that measured by open-circuit voltage decay. The open-circuit voltage decay method gives a better estimation of the minority carrier lifetime provided the variations in diode quality factor are considered while analysing the cell using distributed parameters. The lifetime, measured by the surface voltage decay, has been compared with the reverse recovery method and is approximately the same in both cases. However, it is concluded that for the evaluation of minority carrier lifetime, the surface voltage decay in the current-induced case is more convenient and accurate compared to any other methods reported earlier.