Contactless measurement of current-voltage characteristics for silicon solar cells

The measurement of the current-voltage (IV) characteristics is the most important step for quality control and optimization of the fabrication process in research and industrial production of crystalline silicon solar cells. We propose a methodology to determine the IV characteristics of silicon solar cells in a contactless way. We summarize the theory behind the method, describe the experimental setup and prove the validity of the concept by comparing contactless with conventionally measured IV results. We demonstrate that the differences in open-circuit voltage, short-circuit current, fill factor, and efficiency are smaller than 2.5 %rel for a test set consisting of four passivated emitter and rear cells (PERC cells), two tunnel oxide passivated contact (TOPCon) cells and a silicon heterojunction (SHJ) cell. The methodology eliminates mechanical stress on the solar cells and the time required for contacting the cells, does not require broad busbars for contacting and, hence, enables to reduce the silver consumption, simplifies the measurements of shingle cells and potentially shortens the required time, avoids shading by the contact units and consumable costs for the probes, and yields additional information (reflectance spectrum, quantum efficiency) on the cells compared to conventional IV testing. The methodology might facilitate further applications in the future, e.g., contactless outdoor testing of modules, individual diagnosis of failed cells within a module, and on-the-fly IV measurements of cells.