Photon Tunneling Cascade to Enhance Solar Energy Concentrator in a Sheath/Core Polymer Sheet

ABSTRACT Luminescent solar concentrators (LSCs) enable large‐area solar energy harvesting for photovoltaic applications, yet their performance is fundamentally limited by inefficient photon injection and waveguiding losses. Here, we report a photon tunneling cascade strategy that establishes a synergistic multilayer photon‐management architecture within a sheath/core polymer LSC. In this system, Eu 3 + ‐induced polystyrene‐block‐polyacrylic acid nanoaggregates (EIPAs) are embedded in polyethylene terephthalate (PET) as the photon‐guiding core, while the EIPAs‐doped epoxy sheath provides a luminescent source adjacent to PET and facilitates interfacial coupling. A possible localized evanescent contribution may occur near the EES/PET interface, followed by lightguiding and total internal reflection, with the low‐index outer layer enhancing confinement. A second low‐refractive‐index fluoropolymer sheath (LRS) suppresses surface reflection and photon escape, enabling efficient in‐plane photon transport. The combination of large Stokes shift and high photoluminescence quantum yield (72%) minimizes reabsorption losses and ensures spectral matching with edge‐mounted solar cells. As a result, the optimized E@P‐EL device achieves an optical efficiency (η opt ) of 19.15%, together with a power conversion efficiency of 5.06% at an active area of 11 cm 2 and an average visible transmittance of 67.15%. This work establishes a robust and scalable pathway for high‐performance LSCs through cascade photon tunneling and hierarchical structural design.