Lumped series resistance of solar cells as a result of distributed sheet resistance

Abstract

An analysis of solar cell distributed sheet resistance is performed by solving the nonlinear Poisson equation for the surface potential. Two different approaches to lumped series resistance are discussed: equivalent series resistance R Seq obtained from the cell's equivalent circuit that satisfies the actual current of the cell (all other parameters in the equivalent circuit except the series resistance are kept constant) and Joule series resistance R SJ obtained from the Joule losses in the emitter of the cell. It is observed that the I( U) characteristic obtained from the equivalent circuit that includes R SJ generally disagrees with the actual I( U) characteristic of the solar cell. An additional series resistance R Sadd should be introduced in series with R SJ. Series resistances R SJ, Sadd and R Seq are analyzed numerically in one and two dimensions for different conditions of terminal voltage, illumination and weighted sheet resistance R sh b 2, where b is related to the geometry of the analyzed cell. Following the derivations and the results of the numerical analysis it can be concluded that wherever R SJ varies as a function of terminal voltage, R Sadd should be taken into consideration.