Theory of open-circuit photovoltage decay in a finite base solar cell with drift field

Abstract

A theory of open-circuit photovoltage decay has been developed in a pn junction solar cell by using the Sturm-Liouville R-transform technique. The theory accounts for finite thickness of the base, drift field in the base and a finite surface recombination velocity at the back surface. The theory is applied to analyse some experimental results on photovoltage decay in a solar cell induced by monochromatic light. A good fit is obtained between the theoretical and the experimental results which gives an estimate of excess carrier lifetime, diffusion length and drift field in the base as well as the base thickness. It is shown that the excess carrier lifetime, as determined by the slope of the voltage decay curve, will be an effective lifetime which depends upon the sign and the magnitude of the drift field as well as the thickness of the base.