Studies of surface voltage and current transients in solar cells for accurate evaluation of minority carrier lifetime

Abstract

Surface voltage and current transient are free from depletion region effect of p-n junction solar cell and give more accurate lifetime of minority carriers compared to the other methods. Hence, considering the distributed parameters, an analysis of these transients has been made for forward current-induced case under low-level injection condition. The study is based on switching off the current abruptly to obtain transients after achieving the steady-state condition. The results predicted that the surface voltage and current decay exponentially with time. The calculated time constant of surface voltage transient is equivalent to the lifetime of minority carriers. However, this is valid only when the surface recombination at the back surface is insignificant and also the thickness of the emitter and base regions are not comparable to the diffusion length of the minority carriers. In case of surface current decay, the time constant also depends upon the injected current and separation of contacts at which the current decay is observed. © 1989.