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Field-effect transistors(FETs) of three diketopyrrolopyrroles(DPP)-based small molecules, 3,6-bis(5-phenylthiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolopyrrole-1,4-dione(PDPPP), 3,6-bis(5-(4-fluorophenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo pyrrole-1,4-dione(FPDPPPF) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo pyrrole-1,4-dione(Bu PDPPPBu), have been studied in this work. Well aligned crystals of the three molecules were grown from para-xylene by droplet-pinned crystallization method. FETs based on these aligned crystals exhibit a hole mobility up to0.19 cm~2 V 1s 1and electron mobility up to 0.008 cm~2 V 1s 1. The achieved hole mobility is of the same order of magnitude as reported highest hole mobility for DPP-based small molecules, but it is much lower than that of the high-performance DPP-based polymers. The relative low mobility is mainly attributed to the rough crystal surfaces with steps and, thus, non-smooth charge transport channels at the interfaces between the crystals and the dielectrics. This work has implications for understanding the low charge mobility of DPP-based small molecules.
Field-effect transistors (FETs) of three diketopyrrolopyrroles (DPP) -based small molecules, 3,6-bis (2-ethylhexyl) pyrrolopyrrole-1,4-dione (PDPPP), 3,6-bis (5- (4-fluorophenyl) thiophene-2-yl) -2,5-bis (2-ethylhexyl) pyrrolo pyrrole- bis (5- (4-n-butylphenyl) thiophene-2-yl) -2,5-bis (2-ethylhexyl) pyrrolo pyrrole- 1,4-dione (Bu PDPPPBu), have been studied in this work. crystals of the three molecules were grown from para-xylene by a droplet-pinned crystallization method. FETs based on these bent crystals exhibit a hole mobility up to 0.19 cm-2 V 1s 1 and electron mobility up to 0.008 cm-2 V 1s 1. The achieved hole mobility is the same order of magnitude as reported for high hole mobility for DPP-based small molecules, but it is much lower than that of the high-performance DPP-based polymers. The relative low mobility is mainly attributed to the rough crystal surfaces with steps and, thus, non-smooth charge transport channels at the interfaces between the crystals and the dielectrics. This work has implications for understanding the low charge mobility of DPP-based small molecules.