Researchers from Saudi Arabia's King Abdullah University of Science and Technology (KAUST) have conducted a series of tests to see if the temperature coefficient of the short circuit current in perovskite-silicon tandem solar cells could be a proper standard of measurement to analyze their behavior and performance. The team has come to the conclusion that it may not be considered a proper metric to assess these devices’ performance and behavior.
The scientists explained that the idea of their recent paper was to show that the temperature coefficient of the short circuit current, measured under standard illumination conditions, might not well describe the actual operation of tandem solar cells. Depending on the local spectrum and the temperature range, the current at maximum power (Impp) can increase, decrease or have a mixed behavior. This intriguing effect can help the community to better understand their outdoor data as outdoor tandem operation should become more and more common in the next years.
The research group reported the results of a series of tests conducted on a 29.0%-efficient tandem perovskite-silicon device at temperatures ranging from 25 C to 65 C. Their work also opens the discussion on how to best describe the temperature coefficient in perovskite-silicon or perovskite-CIGS tandems, as it is a key metric given in any module datasheet, the team mentioned.
The scientists also reported that they were not able to predict changes in the current of the tandem cells under real outdoor operation as accurately as for single-junction devices. In particular, they found that factors such as the external quantum efficiency (EQE) of the perovskite subcells, the bandgap of the perovskite, the local solar spectrum, and the operating temperature range are the factors making the assessment of the temperature coefficients critical.
