An A−D−A oligomer, DTS(F 2 BT) 2 , was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F 2 BT) 2 is stepwise and kinetically slow. Both rapid drying and the presence of PC 71 BM trapped DTS(F 2 BT) 2 in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F 2 BT) 2 thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F 2 BT) 2 . In OPV devices, DIO additive drove the DTS(F 2 BT) 2 domains in the DTS(F 2 BT) 2 :PC 71 BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A−D−A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.

Structural analysis of PTh4FBT suggested that the highly crystalline nature of PTh4FBT is related to its zero c-shift co-facial packing.