Quantitative analysis and extraction of cell parameters from interconnected thin-film solar modules through LBIC-voltage sweeps

Light or LASER beam induced current (LBIC) mapping is a useful technique for imaging of spatial non-uniformities within photovoltaic devices. Imaging integrated modules, measured photocurrents can vary widely from one cell to the next depending upon the voltage bias applied to the primary anode and cathode. Such variation with bias suggests the possibility of characterizing individual interconnected cells using LBIC. We have analyzed the voltage bias sensitivity of I_LBIC to obtain specific quantitative values of shunt resistance (R_sh) and unique signatures of high and low diode saturation current (J_o). This allows LBIC to be applied to failure analysis, quality control, and accelerated life testing of completed modules where electrical access to individual cells is not possible. The application of this method of analysis can be used for all integrated module photovoltaic technologies, not just thin films.