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.