Stepwise Structural Evolution of a DTS-F2BT Oligomer and Influence of Structural Disorder on Organic Field Effect Transistors and Organic Photovoltaic Performance

Abstract

An A-D-A oligomer, DTS(F2BT)(2), was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F2BT)(2) is stepwise and kinetically slow. Both rapid drying and the presence of PC71BM trapped DTS(F2BT)(2) in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F2BT)(2) thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F2BT)(2). In OPV devices, DIO additive drove the DTS(F2BT)(2) domains in the DTS(F2BT)(2):PC71BM 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.