The Effects of Molecular Packing Behavior of Small-Molecule Acceptors in Ternary Organic Solar Cells

Herein, two diketopyrrolopyrrole (DPP)-based, small-molecule isomers, o- and p-DPP-PhCN, were introduced as acceptors in ternary organic solar cells (OSCs). The isomers have the same molecular backbone but differ positions of cyanide (CN) substituents (ortho para), which greatly affects their packing behavior. Ternary composed poly(3-hexylthiophene) (P3HT):DPP-PhCN:phenyl-C61-butyric acid methyl ester (PCBM) fabricated, effects different behaviors third component on device performance working mechanism investigated. addition o-DPP-PhCN with a relatively high-lying lowest unoccupied orbital energy level resulted an increase open-circuit voltage (VOC) devices, demonstrating alloy-like structure (o-DPP-PhCN PCBM) system. However, p-DPP-PhCN-based exhibited VOC values similar to that P3HT:PCBM binary cell, irrespective indicating cascade energy-level system effective charge transfer from P3HT PCBM. Importantly, by increasing short-circuit current density increased substantially, resulting pronounced shoulder peaks external quantum efficiency responses long-wavelength region, corresponding contribution photocurrent generated light absorption p-DPP-PhCN. Despite sharing backbone, DPP-PhCNs substantially according position CN substituents, also affected devices fabricated using component.