Spectral response of solar-cell structures

Abstract

The purpose of this study was to measure the spectral response of silicon solar-cell structures, and to observe how the response varied with the depth of the p-n junction. Spectral response was defined as the relative short-circuit current as a function of the wavelength of incident light for equal energy incident upon the cell at all wavelengths. Cells were made with the junction depths varying from 0·6 to 5·0 μ, and having both smooth (etched) surfaces and rough (lapped) surfaces. Response curves from these cells are presented. These curves indicate that in order to increase the relative short-wavelength response (λ<0·75 μ) the junction should be made closer to the surface, while in order to increase the relative long-wavelength response (λ>0·75 μ) the junction must be made comparatively far below the surface. The effect of having a lapped surface on the cell is to reduce the lifetime near the surface, thus reducing the response to short wavelengths of incident light. A simple theoretical model is presented which appears adequately to describe the mechanism involved in determining the shape of the response curves.