Reverse-bias challenges facing perovskite-silicon tandem solar cells under field conditions

Accessible overviewPerovskite-based solar cell technologies have realized outstanding power conversion efficiencies. However, their commercial deployment is hindered by stability issues that include performance degradation caused by oxygen, moisture, ultraviolet light, elevated temperatures, and reverse bias. Cells in a module can become reverse biased, e.g., in a partially shaded cell string, potentially causing irreversible damage. Conventional solutions applied in silicon modules are not suitable for perovskite modules. Perovskite-silicon tandem cells were believed to be reverse-bias resilient. However, these tandems may break down at much lower reverse-bias voltages under fielded conditions, such as in late, sunny afternoons when the solar spectrum is red rich. As the momentum for commercialization continues to grow, such fielded stability issues are destined to become ever more important to resolve. This perspective identifies the additional challenges to reverse-bias resilience under field conditions, showing how cell breakdown can become more likely with varying spectra and temperature, and discusses preventive measures in the context of maximal power output, including comprehensive considerations of string and cell specifications as well as combined methods to give more options.SummaryPerovskite-based solar cells have demonstrated outstanding energy conversion efficiencies but have stability issues, in particular the potential for catastrophic failure under reverse bias. In addition to delivering efficiencies beyond the Shockley-Queisser limit for single-junction cells, monolithic perovskite-silicon tandem cells were recently shown to be resilient to reverse bias under test conditions. However, reverse-bias stability under field conditions—where devices often perform differently than in test conditions, especially when connected to form modules and operating at maximum power output—needs to be addressed for these tandems to become commercially viable. This perspective identifies the additional challenges to reverse-bias resilience under field conditions, showing how cell breakdown can become more likely with varying spectra and temperature, and discusses solutions for addressing these issues in the context of maximal power output from prospective modules, including comprehensive considerations of string and cell specifications, where cell bifaciality, triple junctions, and the booster effect of luminescent coupling are also discussed. These analyses provide clear guidance on how to develop efficient perovskite-silicon tandem cells and, eventually, modules that can operate stably outdoors.