Tracing the Energy Losses in All‐Perovskite Tandem Solar Cells From Opto‐Electro‐Thermal Perspectives

Abstract Tandem solar cells (TSCs) can break the thermodynamic limits of single‐junction SCs, yet their actual performance remains far below expectations. Uncovering the pathways and intrinsic physics behind these energy losses is critical to figuring out effective manipulation strategies for further improving device performance. Here, a tightly coupled opto‐electro‐thermal study on all‐perovskite TSCs is reported which allows for readily tracing the detailed processes of the solar energy conversion from photon absorption to charge‐carrier dynamics and heat generation/dissipation. These findings reveal that while TSCs significantly reduce thermalization heat, they simultaneously increase Joule, Peltier, and recombination heats, leading to greater heat generation and elevated operating temperatures. By identifying the primary heat generation sources and mechanisms, heat dissipation is further explored in TSCs through spatial heat distribution and temperature gradient analysis. The results indicate that the wide‐bandgap and narrow‐bandgap perovskite layers, along with the wide‐bandgap perovskite‐related interfaces, act as primary heat sources, highlighting the need to improve perovskite thermal conductivity. Moreover, heat management strategies are validated through conventional structural and material optimizations. From the optical, electrical, and thermal perspectives, a targeted roadmap is outlined to improve the efficiency of all‐perovskite TSCs to ≈35%, offering valuable insights for the advancement of high‐performance TSCs.