Platinum‐Complex Acceptor Modulating Dielectric Constant and Exciton‐Vibration Coupling for High‐Efficiency Organic Solar Cells with Suppressed Energy Loss

Abstract Excessive energy loss ( E loss ) remains a primary bottleneck limiting further efficiency improvements in organic solar cells (OSCs). Mitigating energy losses is therefore a key prerequisite for advancing organic photovoltaic technologies. Rational acceptor molecular design that modulates the dielectric constant and exciton‐vibration coupling of the active layer has emerged as a particularly promising route to achieving this goal. Herein, a platinum‐complex‐based non‐fullerene acceptor (PtHD) is designed and synthesized. The molecule features high planarity and backbone rigidity, which effectively suppresses exciton‐vibration coupling. Integrating the Pt coordination unit amplifies the molecular dipole moment and polarizability, consequently enhancing the dielectric constant of the active layer. A binary device based on D18/PtHD achieves a high open‐circuit voltage of 0.938 V with a reduced E loss of 0.525 eV. Building on this achievement, by introducing PtHD as a guest component into the D18/L8‐BO system and employing a layer‐by‐layer deposition strategy to control the vertical distribution, the ternary device demonstrates an minimized E loss and superior exciton separation, culminating in a remarkably high power conversion efficiency (PCE) of 20.52%. This work highlights the crucial role of metal‐complex acceptors in managing energy loss and charge dynamics, thus providing a molecular design paradigm to develop highly efficient organic photovoltaics.