Methods for Measuring Solar Cell Efficiency Independent of Reference Cell or Light Source

Accurate measurement of the photovoltaic conversion efficiency under standard test conditions is essential for meaningful comparisons of the device performance of different types of solar cells. A methodology is presented for calibrating reference cells and calculating spectral mismatch factors, and then using these to obtain the corrected short-circuit current with respect to standard test conditions. Using this technique, the current, and hence efficiency, of a given photovoltaic device can be measured with an accuracy of better than 2%, independent of the spectral response of the reference cell or the spectral irradiance of the light source. A second method does not use a reference cell, but depends on an absolute spectral irradiance measurement, and has an accuracy of approximately 5%.