Measurement of diffusion length in solar cells

Abstract

New procedures are described for analyzing diffusion length measurements obtained by using several methods which, in the past, have shown inconsistent results. These procedures consist of a microwave photoconductive decay method and three techniques in which carriers, generated by γ rays, 1‐MeV electrons, or ir light, are collected by a p‐n junction. Special attention is given to measurements of solar cells in which the sample thickness may be comparable to the diffusion length. A theoretical analysis of each method is presented, as well as the results of a study in which a set of solar cells with a wide range of diffusion lengths was measured. It is shown that results from all methods are consistent over the entire range. A discussion of the advantages and disadvantages of the various methods is also included.