Effects of Drift Fields and Field Gradients on the Quantum Efficiency of Photocells

Abstract

A theoretical investigation of the effects of electrostatic drift fields and their gradients in the diffused and base layers of photocells has been carried out. Expressions for the quantum efficiencies of the cell have been derived using a single-region model for the diffused layer and a two-region model for the base layer. Numerical computations for silicon photocells have been performed using impurity profiles of the Gaussian and error-function types. It has been found that there is an improvement in the quantum efficiency of the diffused layer as compared to a field-free layer. The improvement depends upon the diffused impurity profile. It has been deduced that improvement of the base-layer quantum efficiency may be obtained by suitably grading the base-layer impurity concentration. The mathematical analysis in this paper is quite general and may be applied to any photocell by using appropriate values of the parameters of the material of the cell.