Fluorinated-Quinoxaline Based Non-Fused Electron Acceptors Enables Efficient As-Cast Organic Solar Cells.

Non-fused electron acceptors have obtained increasing curiosity in organic solar cells (OSCs) thanks to simple synthetic route and versatile chemical modification capabilities. However, non-fused acceptors with varying quinoxaline core and as-cast device have rarely been explored, and the molecular structure-photovoltaic performance relationship of such acceptors remains unclear. Herein, two non-fused acceptors L19 and L21 with thienyl substituted non-fluorinated/fluorinated quinoxaline core were developed via five-step synthesis. Compared with L19, L21 with F-containing quinoxaline exhibited higher molar extinction coefficient, boosted charge mobility, improved exciton dissociation, more ordered molecular stacking and optimized film morphology. Thereafter, a notable power conversion efficiency (PCE) of 11.45 % could be obtained for the as-cast PBDB-T : L21 -based device, which is significantly better than the device based on PBDB-T : L19 (8.68 %). Furthermore, PM6 : Y6 : L21-based ternary devices were fabricated and exhibited the highest PCE of 17.81 %. This work discloses that the introduction of electron-withdrawing fluorinated quinoxaline core and appropriate side-chain engineering can play an important role in improving the performance of as-cast solar cell devices.