Highly Oriented and Nanotextured Films of Regioregular Poly(3-hexylthiophene) Grown by Epitaxy on the Nanostructured Surface of an Aromatic Substrate

Abstract

A simple method for the nanotexturing and orientation of regioregular poly(3-hexylthiophene) (P3HT) thin films has been developed. Epitaxial growth of P3HT on the surface of an aromatic salt (potassium 4-bromobenzoate) (K-BrBz) leads to highly oriented and nanotextured P3HT films which consist of a regular network of interconnected semicrystalline domains oriented along two preferential in-plane directions. The overall crystallinity and the level of in-plane orientation of the P3HT films are controlled by the temperature of isothermal crystallization (T iso ). Well-defined electron diffraction patterns with sharp reflections obtained for T iso =180 °C indicate that the crystalline domains grow with a unique (1 0 0) P3HT contact plane on the K-BrBz substrate with the P3HT chains oriented along the [0 (2 1] K-BrBz directions of the substrate. During the annealing of the polymer film, the surface of the aromatic salt undergoes a topographic reconstruction resulting in a regular nanostructured "hill and valley" topography that templates and orients the growth of P3HT. Preferred orientation of P3HT crystalline domains occurs at step edges of the substrate and is favored by the matching between the layer period of P3HT and the terrace height of the K-BrBz substrate.

Structure and morphology control in thin films of regioregular poly(3‐hexylthiophene)

“…89 These substrates offer the possibility to melt and anneal the thin films at high temperatures (up to 280 C). This is particularly relevant as the melting temperature of conjugated polymers is usually quite high ($240 C for P3HT).…”

“…14). 89 The overall crystallinity and the level of in-plane orientation of the P3HT films are controlled by the temperature of isothermal crystallization (T iso ). Well-defined ED patterns with sharp reflections obtained for…”

Toward a comprehensive understanding of molecular doping organic semiconductors (review)

“…In the same study, the authors further M a n u s c r i p t 19 investigated the impact of F 4 TCNQ doping on the structural properties of P3HT films. Regioregular P3HT is known to grow in crystalline films exhibiting a lamellar structure with π-stacked polymer chains (stacking distances of 0.39 nm [118] to 0.43 nm [119] depending on the specific polymorph), which are separated by regions filled by the alkyl side-chains [120][121][122][123]. In contrast to the majority of COMs, the full structural details of P3HT are still incomplete, as growing large single-crystals from CPs and applying single-crystal diffraction methods is challenging due to their low structural quality [119].…”

Optical probes of chain packing structure and exciton dynamics in polythiophene films, composites, and nanostructures

“…In crystalline poly(3-hexylthiophene) (P3HT) NFs, the polymer chains are aligned perpendicular to the NF growth axis, with thiophene rings oriented cofacially in adjacent stacks. 24,59,60 P3HT nanofibers are readily made by crystallization in solution by marginalizing the chloroform-solvated polymer with a ''bad'' solvent such as dichloromethane. These species are generated from assembly of individual polymer chains into lamellar sheets (via side-chain interactions) and a secondary packing of the lamellar sheets to form the long nanofiber axis, which can grow to several microns in length.…”