High-Performing Thin-Film Transistors in Large Spherulites of Conjugated Polymer Formed by Epitaxial Growth on Removable Organic Crystalline Templates

Abstract

Diketopyrrolopyrrole (DPP)-based conjugated polymer PDTDPPQT was synthesized and was used to perform epitaxial polymer crystal growth on removable 1,3,5-trichlorobenzene crystallite templates. A thin-film transistor (TFT) was successfully fabricated in well-grown large spherulites of PDTDPPQT. The charge carrier mobility along the radial direction of the spherulites was measured to be 5.46-12.04 cm(2) V(-1) s(-1), which is significantly higher than that in the direction perpendicular to the radial direction. The dynamic response of charge transport was also investigated by applying a pulsed bias to TFTs loaded with a resistor (∼20 MΩ). The charge-transport behaviors along the radial direction and perpendicular to the radial direction were investigated by static and dynamic experiments through a resistor-loaded (RL) inverter. The RL inverter made of PDTDPPQT-based TFT operates well, maintaining a fairly high switching voltage ratio (Vout(ON)/Vout(OFF)) at a relatively high frequency when the source-drain electrodes are aligned parallel to the radial direction.

Molecular Orientation of Conjugated Polymer Chains in Nanostructures and Thin Films: Review of Processes and Application to Optoelectronics

“…The other major advantage of this fabrication process is that it can be applied to virtually any polymer as it does not rely on interactions between TCB and the polymer but rather on the formation of TCB fibers on which the conjugated polymer chains are deposited in a compact arrangement. In fact, as represented in Figure 7, this process can be applied to recently developed conjugated polymers such as PDTDPPQT which should exhibit much higher field-effect mobilities compared to P3HT [42]. In their study on PDTDPPQT, Kim et al fabricated highly crystalline conjugated polymer spherulites which acted as semiconducting layer in PFETs with source and drain electrodes deposited in various position with respect to the center of the spin-coated substrate.…”

Polarized Emission from Conjugated Polymer Chains Aligned by Epitaxial Growth during Off-Center Spin-Coating

“…Epitaxial growth during spincoating using TCB has been previously studied using a diketopyrrolopyrrole-based conjugated polymer to increase the charge transport properties of the polymer used in ptype OFET [9]. The material used displayed strong crystalline peaks without the addition of TCB which, in this case, only induces radial growth and the formation of large spherulites.…”

“…In particular, these materials have the potential to be relatively easily oriented as the polymer chains can be mechanically aligned using a variety of processes [2]. Such processes include the formation of nano-or microfibers by electrospinning [3,4], mechanical rubbing [5,6], unidirectional deposition [7], and epitaxial growth [8,9]. The resulting films often display enhanced optical or charge transport properties and thin films with aligned conjugated polymer chains have consequently been used in a variety of optoelectronic devices such as organic field-effect transistors (OFET) [9], organic solar cell-integrated liquid crystal displays [5], or bipolarized light-emitting diodes [10].…”

“…Such processes include the formation of nano-or microfibers by electrospinning [3,4], mechanical rubbing [5,6], unidirectional deposition [7], and epitaxial growth [8,9]. The resulting films often display enhanced optical or charge transport properties and thin films with aligned conjugated polymer chains have consequently been used in a variety of optoelectronic devices such as organic field-effect transistors (OFET) [9], organic solar cell-integrated liquid crystal displays [5], or bipolarized light-emitting diodes [10]. In particular, epitaxial growth using crystallite templates formed by 1,3,5-trichlorobenzene (TCB) has shown remarkable results when applied to OFET with hole mobilities values 2.75 to 4.66 times higher than those observed in conventionally deposited devices [9].…”

“…The resulting films often display enhanced optical or charge transport properties and thin films with aligned conjugated polymer chains have consequently been used in a variety of optoelectronic devices such as organic field-effect transistors (OFET) [9], organic solar cell-integrated liquid crystal displays [5], or bipolarized light-emitting diodes [10]. In particular, epitaxial growth using crystallite templates formed by 1,3,5-trichlorobenzene (TCB) has shown remarkable results when applied to OFET with hole mobilities values 2.75 to 4.66 times higher than those observed in conventionally deposited devices [9]. However, these values are only obtained from local measurements with interelectrode spacing (channel width) of 80 m. Deposition processes based on TCB can also be applied to the formation of films with polarized light-absorption properties [11], which could, for example, be used in analytical equipment for light-polarization analysis (e.g., cosmic rays).…”