Oligothiophene Organic Thin Film Transistors and Circuits

Abstract

We have investigated a series of α,α'-oligothiophenes with chromophore length ranging from four to six units, and with side chains comprised of ten, six, two, and zero alkyl units. We have fabricated top-contact and bottom-contact organic TFTs with thermally evaporated active layers and found that the TFT performance depends critically on the length of the side chains and on the contact configuration (with mobilities ranging from 0.07 to 1.1 cm2 / V-s), but is relatively insensitive to the chromophore length. We have also fabricated ring oscillators with didecylsexithiophene and measured a signal propagation delay of 30 μsec per stage. In addition, we have fabricated oligothiophene-TFTs with ultra-thin self-assembled monolayer (SAM) gate dielectrics, with the intent to evaluate if long alkyl side chains contribute usefully to the effective thickness of a SAM gate dielectric. We have measured carrier mobilities as large as 0.05 cm2 / V-s and subthreshold swing as low as 200 mV / decade.

Better bottom contact properties in organic field-effect transistors with ultrathin layers

“…7 Carrier mobility values of up to 0.23 cm 2 / V s are reported in the literature for vacuumdeposited films. DH4T has been proven to be well suited as an active material in organic transistors.…”

Rubrene thin-film transistors with crystalline and amorphous channels

“…[1][2][3][4][5][6][7] Since vacuumdeposited thin-film rubrene usually consists of amorphous phase or is hardly crystalline, any reported field mobility of the OTFT with rubrene thin-film channel is still very inferior to those of other OTFTs with previous promising organic channels such as pentacene, tetracene, and alpha-6T. [8][9][10][11] Very recently, polycrystalline rubrene channel was reported to have a high mobility of 0.7 cm 2 / V s as prepared by a special solution treatment. 12 However, studies on rubrene thin films and devices are still lacking.…”

Synthesis and Properties of Molecular Rods. 2. Zig-Zag Rods

“…Halik et al synthesized a series of α,α-N-alkyl-substituted oligothiophenes [ n ] 63 (Chart ) with 4−6 thiophene units and with alkyl side chains ranging from decyl to no alkyl units on each terminus, using Kumada cross-coupling and oxidative coupling conditions. Bäuerle and his group developed a strategy to protect one reactive α position of a 3-dodecylthiophene by employing a terminal benzyl ester group …”