The effect of thermal annealing on the layered structure of smectic liquid crystalline organic semiconductor on polyimide gate insulator and its OFET performance

Heterocycle Effects on the Liquid Crystallinity of Terthiophene Analogues

“…For example, Th-Thd-Th(8) forms a SmC phase over a 34 °C range (95–129 °C), whereas the SmC phase of Th 3 (8) is stable over only a 5 °C range (85–90 °C). As film processing from well-oriented but fluid states (e.g., SmA/C) is advantageous for obtaining uniformly aligned samples [37,58,59] and thermal annealing at elevated temperatures has been shown to improve film morphology [31,48,81], the increased SmC phase stabilities of the thiadiazole derivatives make them attractive candidates for device fabrication.…”

Highly Oriented Liquid Crystal Semiconductor for Organic Field-Effect Transistors

“…For a study of the origin of the increased performance after thermal annealing, out-of-plane XRD was carried out (Figure S8c, Supporting Information). The [002] peak intensity at q z = 0.355 Å –1 increases by 5 times after the annealing process, which means that thermal annealing generates the higher molecular ordering and consequently the higher charge-carrier mobility. − To evaluate the reliability and reproducibility of the FET performance of our platform, we measured the transfer characteristics for different rubbing conditions and temperatures with 10 bottom-gate and bottom-contact transistors on five substrates. As shown in Figure S8, the FET mobility and on/off ratio exhibit minimal variations because of the uniformity of the LC OSC films (Table S1, Supporting Information).…”

High-Performance, Transparent Solution-Processed Organic Field-Effect Transistor with Low-k Elastomeric Gate Dielectric and Liquid Crystalline Semiconductor: Promises and Challenges

“…A comparatively high intensity peak (001), which corresponds to a d-spacing of 5.24 nm, is observed for the samples that are un-annealed, annealed at 120 and 180 0 C. This peak represents the typical bilayer structure of the SmE phase of Ph-BTBT-10. 11,50 Whereas, for the sample annealed at 218 0 C (temperature corresponding to the SmA phase), only a single peak corresponding to the (002) plane is present. This peak corresponds to a d-spacing of 2.61nm, which is the length of one Ph-BTBT-10 molecule, and so the material has a monolayer structure.…”

“…[6][7][8] Gate dielectric plays a crucial role in determining the characteristics of an OFET as the channel is just a few monolayers above the dielectric. 7,[9][10][11][12] In most of the high-performance OFETs reported so far, the conventional inorganic materials such as silicon dioxide (SiO2), aluminum oxide (Al2O3) and so on are used as gate dielectrics along with solution-processed OSCs. [13][14][15][16][17][18][19][20] Though, allsolution-processed OFETs are essential for the realization of low-cost, flexible electronic devices, the development of such OFETs in which both the gate dielectric and the semiconductor are organic materials is difficult to achieve.…”

“…10 Later, Kim et al studied the effect of semiconductor annealing temperatures on the performance of OFETs fabricated with polyimide (PI)/ alumina (Al2O3) gate dielectric. They obtained a maximum mobility of 2.27 cm 2 V -1 s -1 with Ph-BTBT-10 layer annealed at 140 0 C (temperature corresponds to the SmE phase) but the devices operated at a high Vth of ~ -12 V. 11 In all these reports, either a conventional gate dielectric (SiO2) or a bilayer of organic and conventional gate dielectric (PS/ SiO2 and PI/ Al2O3) are used. Implementation of elastomeric gate dielectrics in LC-OFETs is less reported in the literature and since each dielectric-semiconductor interface has its unique features, it would be interesting to investigate how an elastomeric gate dielectric such as PDMS influences the performance of LC-OFETs.…”