Single‐Crystal Polythiophene Microwires Grown by Self‐Assembly

Abstract

Obtaining control over the supramolecular organization of electronically active p-conjugated polymers [1] would make it possible to fine-tune and optimize their electrical properties for applications in organic field-effect transistors (OFETs) [2][3][4][5] and sensors. [6,7] Typically, it is far more challenging to obtain high-quality single crystals of conjugated polymers by facile solution processing than oligomers [8] and small molecules, [9] which are prepared by vacuum processes. However, 1D, highquality, single-crystal semiconductors comparable to inorganic single crystals, such as silicon nanowires, have not hitherto been observed for conjugated polymers. Self-organized poly(3-hexylthiophene) (P3HT), [10][11][12][13][14][15][16][17][18] with its supramolecular 2D structure, is of special interest because the 1D electronic properties of the p-conjugated polymer chains are modified by the increased interchain stacking that results from p-p interactions. Therefore, the possibility of achieving good electrical performance as a result of 2D transport (i.e., band-like transport) in self-organized single-crystal P3HT has spurred its use in enhanced polymer electronic devices (PEDs). By better control of structural anisotropy, and by developing P3HT structures with strongly p-p interacting building blocks coinciding with the direction of current flow in PEDs, optimized electrical performance and, possibly, a truly delocalized transport regime may be attained. We report here the preparation and properties of high-quality, 1D single-crystal P3HT microwires grown by a facile self-assembly process in dilute solution. Figure 1 outlines the fabrication steps for the preparation of low-voltage, gate-modulated PEDs based on well-faceted, 1D single-crystal P3HT microwires. Dense octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs) (structure shown in Fig. 1A) possessing sufficient robustness are used as the molecular dielectrics to reduce the operating voltage of COMMUNICATIONS

Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

“…Due to the difficulty of unfolding chains to a totally extended conformation, there are few examples of preparing conjugated polymer single crystals under strict conditions like concise temperatures, extremely slow evaporation and/or specific substrates, etc. [73][74][75][76][77][78]. Thirdly, according to Einstein-Stokes Equation, D = K B T/6πηa, the diffusion coefficient (D) is inverse to the sizes of moving unit (a) in solutions.…”

“…The nucleation stage plays a determining role in the final morphology according to the order, shape and density of nucleates [77,152,155,159]. An effective strategy to promote the fully crystallization of conjugated polymer chains based on nucleation is self-seeding [53,75,77,152,159]. Self-seeding means the homogeneous formation of nucleates in the supersaturated solution at a relatively higher temperature (T ss ) preventing excessive aggregation followed by a further ordered growth of nucleates into crystals with a larger size at a constant lower temperature (T c ).…”

Fine fibrillar and rectangular/hexagonal ordered grains of poly(3-hexyl thiophene) and poly(ethylene glycol) developed by seeding technique

“…Scanning force microscopy (SFM) images of the surfaces of PEO crystals revealed oriented fibril-like growth with increasing annealing temperature [15]. Recently, polymer single crystals and highly ordered structures have been employed in distinct potential applications including programmable assembly of nanoparticles [16], mimicking the natural bone nanostructures [17], magnetically recyclable catalyst support [18][19][20][21][22], templates to synthesize nanoparticle clusters [23,24], substrates for anisotropic deposition of Au nanoparticles [25], utilizable in semiconductor microelectronics and solid-state [26,27], ultrathin film systems [28], delivery systems for human papilloma virus-associated tumors [29][30][31], nano/micromotors [32,33], and photovoltaic devices [34].…”

Linear optical properties and electronic structures of poly(3-hexylthiophene) and poly(3-hexylselenophene) crystals from first principles

“…[18][19][20] Structural determinations for the Forms I of rr-P3HT (n=6) have been performed on the basis of X-ray/electron diffraction measurements. [21][22][23][24][25][26] Most papers published in the 1990's, only show schematic models and lattice constants of crystal rr-P3AT; none are about internal coordinates and space groups. [18,21,22,27,28] In recent years, a monoclinic structure of rr-P3HT with a P 2 1 /c space group was proposed by small angle electron diffraction measurements.…”