LAUSR

Abstract The application of nanophotonic structures for organic solar cells (OSCs) is quite popular and successful, and has led to increased optical absorption, better spectral overlap with solar irradiances, and improved charge collection. Significant improvements in the power conversion efficiency (PCE) have also been reported, exceeding 11%. Nonetheless, with the given material properties of OSCs with low optical absorption, narrow spectrum, short transport length of carriers, and nonuniform photocarrier generations resulting from the nanophotonic structure, the PCE of single‐junction OSCs has been stagnant over the past few years, at a barrier of 12%. Here, an ultrathin inverted OSC structure with the highest efficiency of ≈13.0%, while being made from widely used organic materials, is demonstrated. By introducing a smooth spatial corrugation to the vertical plasmonic cavity enclosing the active layer, in‐plane propagation modes and hybridized Fabry–Perot cavity modes inside the corrugated cavity are derived to achieve an ultralow Q, uniform coverage of optical absorption, in addition to uniform photocarrier generation and transport. As the first demonstration of ultra‐broadband absorption with the introduction of spatial corrugation to the ultrathin metal film electrode–cathode Fabry–Perot cavity, future applications of the same concept in other light‐harvesting devices utilizing different materials and structures are expected.