Comparison of Double-Side and Equivalent Single-Side Illumination Methods for Measuring the I–V Characteristics of Bifacial Photovoltaic Devices

The equivalent single-side illumination method was proposed as the possible way to measure the bifacial photovoltaic devices. To verify the equivalent single-side illumination method, we compared the current-voltage (I-V) characteristic measurement of bifacial single-cell laminates under double-side and equivalent single-side illumination conditions. The results showed that the short-circuit current (Isc) and the open-circuit voltage (Voc) of each method were almost consistent, whereas the maximum power (Pmax) of the double-side illumination method was higher than that of the single-side method under a range of different combinations of front and rear irradiation. To analyze the reason for this difference, we applied the penalty-based differential evolution method to further extract the one-diode model parameters of bifacial single-cell laminates. Among all the parameters, it was found that the series resistance (Rs) measured with both methods was obviously different. As a result, an Rs-correction model was accordingly proposed to correct the Pmaxmeasured with the equivalent single-side illumination method.