The Impact of Measurement Conditions on Solar Cell Efficiency

Precise solar cell measurements become more and more challenging due to the increasing complexity of metallization patterns and the sensitivity to rear side illumination for bifacial cell concepts. In this context, the measurement conditions under which conversion efficiencies are determined need to be closely examined: Different efficiency values can occur for the same solar cell because of different measurement conditions. To provide more transparency, a notation has recently been published, which unambiguously characterizes the measurement conditions used and which is included in the calibration documents of the calibration laboratories ISFH CalTeC and Fraunhofer ISE CalLab PV Cells. As this notation is held rather technical and no quantitative assessment is given so far, herein, the effects associated with different measurement conditions are analyzed and quantified in detail for typical industrial-type solar cells. It is shown that varying the measurement conditions as well as the busbar concept can lead to significant differences in measured efficiency of 0.5%abs. The power gains coming from different cell measurement configurations do not occur in the same manner on the module level though and can lead to considerable variations in cell-to-module power factors. Several hints to increase the significance of solar cell measurements are given.