Simultaneous optical losses and current measurements in photovoltaic devices at variable angle of the incident light

In this work, the apparatus and the method for a simultaneous measurement of the optical losses and short-circuit current in a solar cell, at variable incidence angle of the light, is presented. The method has been applied to an n+/p c-Si cell with a polished surface. The investigation has been performed over an angular range from 8° to 80°, using a linearly polarized laser beam, either normally or parallelly polarized with respect to the incidence plane. The experimental curves of reflectance seem to be in a good agreement with the theoretical ones derived from the Fresnel equations. Since the measurements are performed inside an integrating sphere, a procedure has been developed to derive, from the total current Itot, the calculated direct one, IdirCal excluding contributions from the incoming light back-diffused to the cell under investigation; the results are compared with real direct-current measurement. Since with the proposed method both reflectance and current are measured for the same surface region and under identical illumination conditions, the results have been combined to get the internal spectral response of the n+/p c-Si polished surface solar cell.