π-Spacer-Linked Bisthienopyrroles with Tunable Optical Properties

Enhancement in Charge Carrier Mobility by Using Furan as Spacer in Thieno[3,2-b]Pyrrole and Alkylated-Diketopyrrolopyrrole Based Conjugated Copolymers

The structural alteration of semiconducting polymer backbones can improve the optoelectronic properties of organic semiconductors and enhance field-effect mobilities. In our efforts towards improving the performance of organic field-effect transistors (OFETs), we are reporting a donor–acceptor polymer containing thieno[3,2-b]pyrrole (TP) donor and a furan-flanked diketopyrrolopyrrole (DPP) electron acceptor, which yielded an asymmetric poly(methylthienopyrrolo)furanyl)diketopyrrolopyrrol) P(FDPP-TP) organic semiconducting polymer. The introduction of a furan spacer improved thermally induced crystallinity and molecular packing, as confirmed by grazing incidence X-ray diffraction (XRD) and tapping-mode atomic force microscopy (TMAFM). The tested OFET devices gave maximum hole mobility of 0.42 cm2 V−1 s−1 with threshold voltages around 0 V for bottom-gate bottom-contact device configuration.

Pyrrole-Containing Semiconducting Materials: Synthesis and Applications in Organic Photovoltaics and Organic Field-Effect Transistors

Organic semiconducting materials derived from π-electron-rich pyrroles have garnered attention in recent years for the development of organic semiconductors. Although pyrrole is the most electron-rich five-membered heteroaromatic ring, it has found few applications in organic photovoltaics and organic field-effect transistors due to synthetic challenges and instability. However, computational modeling assisted screening processes have indicated that relatively stable materials containing pyrrolic units can be synthesized without compromising their inherent electron-donating properties. In this work, we provide a complete, up-to-date review of pyrrole-containing semiconducting materials used for organic photovoltaics and organic field-effect transistors and highlight recent advances in the synthesis of these materials.

Thieno[3,2-b]pyrrole and Benzo[c][1,2,5]thiadiazole Donor-Acceptor Semiconductors for Organic Field-Effect Transistors

Two p-type donor-acceptor (D-A) semiconducting small molecules were synthesized to investigate the effect of the backbone curvature on the organic field-effect transistor performance. The backbone curvature of the donor-acceptor small molecules was modified by changing the spacer group from bithiophene to thienothiophene. Bithiophene to thienothiophene spacer groups were placed between 4H-thieno[3,2-b]pyrrole (donor) and benzo[c][1,2,5]thiadiazole (acceptor) to generate TP-BT4T-TP and TP-BT2TT-TP donor-acceptor molecules. A good charge carrier mobility of 2.59 × 10-2 cm2 V-1 s-1 was measured for the curved molecule (TP-BT4T-TP), while the linear molecule analog (TP-BT2TT-TP) only gave a low mobility of 5.41 × 10-5 cm2 V-1 s-1 after annealing at 120 °C in bottom-contact bottom-gate devices. Out-of-plane grazing-incidence X-ray diffraction analysis revealed more drastic thermally induced crystallinity for TP-BT4T-TP as compared to TP-BT2TT-TP, explaining the difference observed in the performance of devices fabricated from each molecule.