RESUMEN
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.
RESUMEN
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.
RESUMEN
We report two banana-shaped organic semiconducting small molecules containing the relatively unexplored thieno[3,2- b]pyrrole with thiophene and furan flanked benzothiadiazole. Theoretical insights gained by DFT calculations, supported by single crystal structures show that furan flanked benzothiadiazole-thieno[3,2- b]pyrrole small molecule has a higher curvature compared to the thiophene flanked small molecule due to the shorter carbon-oxygen bond in furan. Despite similar optical and electrochemical properties, thiophene flanked small molecule shows average hole mobility up to 8 × 10-2 cm2 V-1 s-1, however furan flanked small molecule performs poorly in thin film transistor devices (µh ≈ 5 × 10-6 cm2 V-1 s-1). The drastic difference in hole mobilities was due to the annealing-induced crystallinity which was demonstrated by the out-of-plane grazing incidence X-ray diffraction and surface morphology studies by tapping mode atomic force microscopy analysis.
RESUMEN
Recent advancements in organic field effect transistors have switched chemists' focus from synthesizing libraries of organic semiconductors to a more targeted approach where chemical alterations are performed on known semiconductors to further improve electronic properties. Among successful semiconducting polymer candidates, copolymers based on diketopyrrolopyrrole-and thieno[3,2-b]thiophene [P(DPP-TT)] have been subjected to modifications on the diketopyrrolopyrrole unit by using flanking groups and side chain engineering. Thieno[3,2-b]thiophene moiety, however, has seen minimal modifications due to the limited number of modifying sites. Isoelectronic thieno[3,2-b]pyrrole could serve as an alternative since it is easily tunable via N-alkylation reactions. Therefore, for the first time, we report the replacement of the thieno[3,2-b]thiophene unit of P(DPP-TT) with thieno[3,2-b]pyrrole unit and its performance in p-channel field effect transistors. The copolymer exhibits linear characteristics to achieve a relatively high average hole mobility of 0.12 cm2 V-1 s-1 in bottom-gate/top-contact field effect transistors with threshold voltages as low as 0 V. These preliminary results highlight the potential of this thieno[3,2-b]pyrrole monomer for utilization in organic field effect transistors.