Nanocrystal-tailored recombination for all-perovskite tandem solar modules

The commercialization of all-perovskite tandem solar modules is hindered by the reliance on the conventional gold-based tunnel recombination junction^1,2. Specifically, this tunnel recombination junction introduces substantial near-infrared parasitic absorption³ and suffers from interfacial instability⁴, limiting both photocurrent generation and operational durability. Here, we develop a solution-processed interconnecting layer based on surface-engineered indium oxide nanocrystals featuring high optical transparency, in which controlled nanocrystal morphology and tailored ligand chemistry enable smooth interfacial contact and favourable energy-level alignment. We introduce a phosphonic acid additive into the lead-tin perovskite precursor, which synergistically improves the electronic contact with the indium oxide recombination layer, thereby enhancing hole extraction. Moreover, the additive regulates perovskite crystallization to mitigate residual strain during film formation, ensuring high-quality large-area deposits. This coordinated interfacial and crystallization engineering strategy simultaneously enhances carrier recombination efficiency at the interconnection layer, improves carrier extraction and promotes large-area film uniformity in all-perovskite tandems. As a result, a 65-cm² all-perovskite tandem solar module achieves a certified power conversion efficiency of 26.2% (ref. ⁵), with 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 in terms of averaged subcell performance, measured by the Japan Electrical Safety and Environment Technology Laboratories. This marks a notable advance towards scalable perovskite tandem photovoltaics.