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Thieno[3,2-b]pyrrole-benzothiadiazole Banana-Shaped Small Molecules for Organic Field-Effect Transistors

Bulumulla, Chandima, Gunawardhana, Ruwan, Kularatne, Ruvanthi N., Hill, Madison E., McCandless, Gregory T., Biewer, Michael C., Stefan, Mihaela C.
ACS applied materials & interfaces 2018 v.10 no.14 pp. 11818-11825
X-ray diffraction, atomic force microscopy, crystal structure, electrochemistry, materials science, pyrroles, thiophene, transistors
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.