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

We report two banana-shaped organic semi-conducting 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 X 10(-2) cm(2) V-1 s(-1) however furan flanked small molecule performs poorly in thin film transistor devices (mu(h) approximate to 5 x 10(-6) cm(2) 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.