Detailed analysis and contact properties of low-voltage organic thin-film transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) and its didecyl and diphenyl derivatives

Low-voltage organic thin-film transistors (TFTs) based on four different small-molecule semiconductors (pentacene, DNTT (dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene), C-10-DNTT and DPh-DNTT) were fabricated, and a detailed comparison of the semiconductor thin-film morphology, of the current-voltage characteristics of transistors with channel lengths ranging from 100 to 1 mu m, and of the contact resistances is provided. The three thienoacene derivatives DNTT, C-10-DNTT and DPh-DNTT all have significantly larger charge-carrier mobilities and smaller contact resistances than pentacene. In terms of the intrinsic channel mobility (determined using the transmission line method), C-10-DNTT and DPh-DNTT perform quite similarly and notably better than DNTT, suggesting that the decyl substituents in C-10-DNTT and the phenyl substituents in DPh-DNTT provide a similar level of enhancement of the charge-transport characteristics over DNTT. However, the DPh-DNTT TFTs have a substantially smaller contact resistance than both the DNTT and the C-10-DNTT TFTs, resulting in notably larger effective mobilities, especially in transistors with very small channel lengths. For DPh-DNTT TFTs with a channel length of 1 mu m, an effective mobility of 0.68 cm(2)/V was determined, together with an on/off ratio of 108 and a subthreshold swing of 100 mV/decade. (C) 2016 Elsevier B.V. All rights reserved.