Breakthrough in Perovskite Solar Modules Achieves Record Efficiency with Nanocrystal-Tailored Recombination

The commercialization of advanced all-perovskite tandem solar modules has long been hampered by a critical bottleneck: the reliance on conventional gold-based tunnel recombination junctions (TRJs). These traditional junctions introduce significant near-infrared parasitic absorption, which directly limits the amount of photocurrent generated. Furthermore, they suffer from inherent interfacial instability, compromising the long-term operational durability and overall performance of the solar cells. Addressing these fundamental challenges has been paramount for unlocking the full potential of perovskite technology. In a significant stride forward, researchers have developed a novel solution-processed interconnecting layer designed to overcome these limitations. This innovative layer is based on surface-engineered indium oxide (In2O3) nanocrystals, meticulously crafted to offer exceptional optical transparency. The precise control over the nanocrystal morphology and tailored ligand chemistry enables the formation of incredibly smooth interfacial contacts, ensuring optimal energy level alignment crucial for efficient charge transfer within the module. A key element of this breakthrough involves the strategic introduction of a phosphonic acid additive into the lead–tin (Pb–Sn) perovskite precursor solution. This additive plays a synergistic role, dramatically improving the electronic contact with the In2O3 recombination layer and, consequently, enhancing the extraction of holes – a vital process for maximizing current. Beyond its role in carrier extraction, the phosphonic acid additive also meticulously regulates perovskite crystallization, effectively mitigating residual strain that typically arises during film formation, thereby guaranteeing the production of high-quality, uniform large-area deposits. This coordinated engineering strategy, which simultaneously addresses both interfacial contact and crystallization processes, yields multifaceted benefits. It significantly enhances carrier recombination efficiency at the interconnection layer, streamlines carrier extraction, and crucially promotes large-area film uniformity across all-perovskite tandem structures. These improvements collectively contribute to a more robust, efficient, and scalable solar module design, paving the way for broader adoption. The efficacy of this new approach has been rigorously demonstrated through impressive performance metrics. A 65-cm² all-perovskite tandem solar module, utilizing this advanced technology, achieved a certified power conversion efficiency of 26.2%. This remarkable figure was independently verified by the Japan Electrical Safety and Environment Technology Laboratories (JET). The module also exhibited an open-circuit voltage of 2.182 V, a fill factor of 77.4%, and a short-circuit current density of 15.6 mA cm⁻², based on averaged subcell performance. These results mark a significant and promising advance toward the realization of scalable and commercially viable perovskite tandem photovoltaics.