Solution‐Crystallized Organic Field‐Effect Transistors with Charge‐Acceptor Layers: High‐Mobility and Low‐Threshold‐Voltage Operation in Air

Abstract

High‐mobility solution‐processed organic transistors are developed based on a hybrid of solution‐crystallized air‐stable organic semiconductor 2,7‐dioctyl[1]ben­zo­thieno[3,2‐b][1] benzothiophene (C8‐­ BTBT) and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetra­cy­anoquinodimethane (F4‐TCNQ) top layers. Charge mobility as high as 6 cm2/Vs is achieved, owing to the almost perfectly periodic crystal packing and efficient charge supply from the acceptor.

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method

“…Interestingly, it was also noticed that the preferred growth direction of the OCSC film is along the (010) direction of the C8-BTBT crystal (Supplementary Note 1 and Supplementary Fig. 4), which is different from what previously reported, i.e., (100) or (110) directions being the preferred growth direction 24,25 .…”

“…The higher mobilities we obtained here is unlikely to be only attributed to a larger grain size as compared with previous studies, where single crystals were used in the channels 18,24,25 . Several additional factors may be contributing to the extremely high mobility: the highly aligned crystalline thin film, more continuous formation of C8-BTBT film due to the presence of the PS layer, passivation effect of the PS and possibly the meta-stable packing structure.…”

“…16). The observed isotropic mobility is reasonable because the charge transfer integrals along different directions are roughly balanced 16,24 . However, the high degree of alignment will still be a contributing factor to the high mobility value because such an alignment reduces the grain boundary scattering 30 .…”

Small Molecule/Polymer Blend Organic Transistors with Hole Mobility Exceeding 13 cm2 V−1 s−1

“…[5] [7] [22] As the complementary polymer binder we selected the indacenodithiophene-benzothiadiazole (C16IDT-BT) [ Figure 1(a)] primarily due to its good solubility, high hole mobility (3.6 cm 2 /Vs) [23] [24] [25] and comparable highest occupied molecular orbital (HOMO) energy level to that of the C8-BTBT [ Figure 1(b)]. [26] [27] Using this unique combination of materials we have demonstrated solution-processed OTFTs with hole mobility values in excess of 13 cm 2 /Vs. Key to our success is the incorporation of a [28] [29] which acts as both a p-dopant and an electron scavenger.…”

Crystals in Materials Science

“…44 Patterned growth is achieved by using a pre-patterned, self assembled monolayer as a growth template. Takeya and coworkers have introduced an oriented growth method 3,45 where an inclined substrate and a "liquid-sustaining piece" allow high quality crystals to form on a SiO2 coated substrate. The resulting materials were single crystalline as confirmed by X-ray diffraction and gave mobilities on the order of 2 -6 cm 2 /Vs.…”