High‐Performance Single Crystal Organic Field‐Effect Transistors Based on Two Dithiophene‐Tetrathiafulvalene (DT‐TTF) Polymorphs

Abstract

Solution prepared single crystal organic field-effect transistors (OFETs) combine low-cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution-prepared single crystal OFETs based on two different polymorphs of dithiophene-tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X-ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the -phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules.

Restraints in low dimensional organic semiconductor devices at high current densities

“…Mat.). As expected and in agreement with previous results [7], the field-effect mobility of SC1 is about two orders of magnitude higher compared to TF1, which is related to its higher degree of crystallinity and the absence of grain boundaries. Differences in device performance in all the devices fabricated were not significant.…”

“…Dithiophene-tetrathiafulvalene (DT-TTF) [5] was chosen as active material to prepare both thin-film and single-crystal OFETs [6,7]. OFETs were prepared on highly doped silicon wafers with 200 nm of thermally grown Si/SiO 2 using both bottom-gate top-contact and bottomgate bottom-contact architectures.…”

“…Fifty nm thick DT-TTF films were thermally evaporated on top of a octadecyltrichlorosilane modified SiO 2 surface at a deposition rate of 1-2Å/s. Single-crystals of DT-TTF were grown from a chlorobenzene solution (c = 1 mg/ml) as described previously [7]. Kelvin probe microscopy (KPM) measurements were performed using commercial conductive diamond coated Si tips (Nanosensors) with a Veeco microscope operated under ambient conditions connecting a Keithley 2636 SourceMeter for OFET characterization [8].…”

Tuning crystal polymorphs of a π-extended tetrathiafulvalene-based cruciform molecule towards high-performance organic field-effect transistors

“…However, using toluene as the solvent promoted the platelet/block-shaped β-phase, and IF-TTF single crystals were formed generally with length of tens micrometers and width of several micrometers (Fig. 2b), indicating the strong solvent effect on molecular aggregation [23] and further assembly for IF-TTF, which is very popular for TTF-derived molecules [31][32][33] and other organic systems [34][35][36]. Fortunately, by carefully controlling the slow solvent evaporation from their corresponding saturated chloroform or toluene solution for crystal growth, enough large ribbon (named as α-phase) and block (named as β-phase) single crystals of IF-TTF were successfully obtained separately for single crystal data analysis.…”

Organic Charge-transfer Salts and the Component Molecules in Organic Transistors

“…30 DT-TTF also shows polymorphs, where the newly found thin-film ¢-phase exhibits lower performance by one order. 31 Similar solution processess have been applied to many TTF derivatives. 32 Although BEDT-TTF (bis(ethylenedithio)TTF) exhibits relatively low mobility (0.005 cm 2 V ¹1 s…”