Correlation between Crystal Structure and Mobility in Organic Field-Effect Transistors Based on Single Crystals of Tetrathiafulvalene Derivatives

Abstract

Recently, it was reported that crystals of the organic material dithiophene-tetrathiafulvalene (DT-TTF) have a high field-effect charge carrier mobility of 1.4 cm(2)/(V x s). These crystals were formed by a simple drop-casting method, making this material interesting to investigate for possible applications in low-cost electronics. Here, organic single-crystal field-effect transistors based on materials related to DT-TTF are presented and a clear correlation between the crystal structure and the electrical characteristics is observed. The observed relationship between the mobilities in the different crystal structures is strongly corroborated by calculations of both the molecular reorganization energies and the maximum intermolecular transfer integrals. The most suitable materials described here exhibit mobilities that are among the highest reported for organic field-effect transistors and that are the highest reported for solution-processed materials.

Solution-processed, high-performance n-channel organic microwire transistors

“…To the best of our knowledge, this is the highest mobility for n-channel transistors based on organic single crystal wires prepared by solution processing. It is comparable with the highest mobility of p-channel organic wires prepared by solution processing (20)(21)(22), as well as to the best performance of n-channel single-crystal organic transistors prepared with a free-space gate dielectric (43). Additionally, this mobility is approximately 10 times higher than that of vacuum-evaporated thin-film devices (0.1 cm 2 /Vs) of the same molecules (39).…”

“…These unique materials combine the high-performance of singlecrystalline structures with solution-processability by dispersion (17,18). Several p-channel (hole-transporting) organic wires prepared by solution-processing have exhibited Ͼ 0.1 cm 2 /Vs for singlewire transistors (19)(20)(21)(22), whereas only a few solution-synthesized n-channel organic wires have been reported, typically with low performance ( Ϸ10 Ϫ3 Ϫ 10 Ϫ2 cm 2 /Vs) (23,24).Despite the intrinsic high mobility of single-crystalline wires, precise wire placement and wire-to-wire performance variation, due to the difference in the contact quality at the wire/insulator and wire/electrode interfaces, substantially hinder successful device integration (10, 25). Therefore, the technology to achieve network films of organic MWs deposited from a dispersion with controlled alignment and density is acutely desired.…”

“…These unique materials combine the high-performance of singlecrystalline structures with solution-processability by dispersion (17,18). Several p-channel (hole-transporting) organic wires prepared by solution-processing have exhibited Ͼ 0.1 cm 2 /Vs for singlewire transistors (19)(20)(21)(22), whereas only a few solution-synthesized n-channel organic wires have been reported, typically with low performance ( Ϸ10 Ϫ3 Ϫ 10 Ϫ2 cm 2 /Vs) (23,24).…”

Organic field-effect transistors using single crystals

“…It was pointed out that the higher solubility of these materials should be advantageous for their use in low-cost solution processing [57]. In fact, SC-OFETs were fabricated by solution processing for some kinds of TTF analogues [64][65][66][67].…”

Theoretical study of the effects of different substituents of tetrathiafulvalene derivatives on charge transport

“…These derivatives exhibit excellent charge transfer properties, the highest charge mobility of which was reported to be 3.6 cm 2 /(V s) [16]. Mas-Torrent et al [17,18] studied dithiophene-tetrathiafulvalene (DT-TTF) and dibenzo-tetrathiafulvalene (DB-TTF), which contain similar molecules but present different crystal packing types, and found that different intermolecular interactions significantly influence the electronic transport properties of the compounds. Naraso et al [19] found that OFET devices based on halogeno-substituted quinoxaline rings fused with TTF show excellent n-type performance and high carrier mobility.…”