A new class of additive materials bis(pentafluorophenyl) diesters (BFEs) where the two pentafluorophenyl (CF) moieties are attached at the both ends of a linear aliphatic chain with tunable tether lengths (BF5, BF7, and BF13) were designed and synthesized. In the presence of BF7 to restrict the migration of fullerene by hand-grabbing-like supramolecular interactions induced between the CF groups and the surface of fullerene, the P3HT:PCBM:BF7 device showed stable device characteristics after thermal heating at 150 °C for 25 h. The morphologies of the active layers were systematically investigated by optical microscopy, grazing-incidence small-angle X-ray scattering (GISAXS), and atomic force microscopy. The tether length between the two CF groups plays a pivotal role in controlling the intermolecular attractions. BF13 with a long and flexible tether might form a BF13-fullerene sandwich complex that fails to prevent fullerene's movement and aggregation, while BF5 with too short tether length decreases the possibility of interactions between the CF groups and the fullerenes. BF7 with the optimal tether length has the best ability to stabilize the morphology. In sharp contrast, the nonfluorinated BP7 analogue without CF-C physical interactions does not have the capability of morphological stabilization, unambiguously revealing the necessity of the CF group. Most importantly, the function of BF7 can be also applied to the high-performance PffBT4BT-2OD:PCBM system, which exhibited an original PCE of 8.80%. After thermal heating at 85 °C for 200 h, the efficiency of the PffBT4BT-2OD:PCBM:BF7 device only decreased slightly to 7.73%, maintaining 88% of its original efficiency. To the best of our knowledge, this is the first time that the thermal-driven morphological evolution of the high-performance PffBT4BT-2OD polymer has been investigated, and its morphological stability in the inverted device can be successfully preserved by the incorporation of BF7. This research also demonstrates that BF7 is not only effective with PCBM but also to PCBM.

Two-dimensional alkylated αβ-TTN and βα-TTN were designed and synthesized. The cross-shaped αβ-TTN and βα-TTN moieties were polymerized to afford two isomeric polymers, Pαβ-TTNFBT 40 and Pβα-TTNFBT 40 . Pαβ-TTNFBT 40 using an α-aNDT unit in the main chain exhibited more red-shifted absorption and a smaller HOMO/LUMO band gap than Pβα-TTNFBT 40 using β-aNDT in the main chain. Compared to Pβα-TTNFBT 40 showing a curved backbone, density functional theory (DFT) calculations revealed that Pαβ-TTNFBT 40 exhibited a quasi-linear polymeric backbone that induces stronger intermolecular interactions and higher molecular ordering in the solid state. Pαβ-TTNFBT 40 exhibited an organic field-effect transistor (OFET) hole mobility of 1.12 × 10 −2 cm 2 V −1 s −1 , which outperformed Pβα-TTNFBT 40 by 1 order of magnitude (1.60 × 10 −3 cm 2 V −1 s −1 ). Through side-chain engineering and optimization, Pαβ-TTNFBT 24 using a shorter 2-butyloctyl side chain further strengthened the intermolecular interactions. From grazing incidence wide-angle X-ray scattering (GIWAXS), Pαβ-TTNFBT 24 adopted an edge-on π−π stacking orientation in a thin film, leading to an improved mobility of 1.75 × 10 −1 cm 2 V −1 s −1 , which has exceeded the mobility of the one-dimensional α-aNDT-based PaNDTDTFBT (4.70 × 10 −2 cm 2 V −1 s −1 ). This research demonstrated that the twodimensional structure is an effective strategy to achieve higher OFET mobility, and the geometry of the main chain played a more significant role than that of the side chain in determining the physical and packing properties of polymers.