Ultrasound-Induced Ordering in Poly(3-hexylthiophene): Role of Molecular and Process Parameters on Morphology and Charge Transport

Abstract

Facile methods for controlling the microstructure of polymeric semiconductors are critical to the success of large area flexible electronics. Here we explore ultrasonic irradiation of solutions of poly(3-hexylthiophene) (P3HT) as a simple route to creating ordered molecular aggregates that result in a one to two order of magnitude improvement in field effect mobility. A detailed investigation of the ultrasound induced phenomenon, including the role of solvent, polymer regioregularity (RR) and film deposition method, is conducted. Absorption spectroscopy reveals that the development of low energy vibronic features is dependent on both the regioregularity as well as the solvent, with the latter especially influential on the intensity and shape of the band. Use of either higher regioregular polymer or ultrasonic irradiation of lower regioregular polymer solutions results in high field effect mobilities that are nearly independent of the dynamics of the film formation process. Surprisingly, no distinct correlation between thin-film morphology and macroscopic charge transport could be ascertained. The relationships between molecular and process parameters are very subtle: modulation of one effects changes in the others, which in turn impact charge transport on the macroscale. Our results provide insight into the degree of control that is required for the development of reproducible, robust materials and processes for advanced flexible electronics based on polymeric materials.

Influence of Molecular Conformations and Microstructure on the Optoelectronic Properties of Conjugated Polymers

“…Such a picture would be consistent with more recent work where, also, ultrasonication was exploited to process P3HT. In this study, it was shown that the μ FET of P3HT increased by one order of magnitude for material of higher molecular weight (from 1.16 × 10 −3 cm 2 V −1 s −1 to 2.73 × 10 −2 cm 2 V −1 s −1 for a molecular weight of 47.7 kDa), although no clear correlation between thin-film microstructure and macroscopic charge transport could be established [38]. …”

Photoinduced Anisotropic Assembly of Conjugated Polymers in Insulating Polymer Blends

“…7,12,[16][17] However, as polymer regioregularity (RR) and/or MW increases, it becomes difficult to completely dissolve the semiconductor in a marginal solvent even at higher temperatures; [18][19][20][21][22] and it is these high RR and MW polymers that are more desirable for opto-electronic applications because of their improved electrical properties. 20,[22][23][24] The approach using good/poor solvent mixtures requires substantial optimization to determine the appropriate mixed solvent composition for a given polymer semiconductor (i.e., different RR or MW) in order to maximize performance. In addition, the above approaches do not provide sufficient time for favorable 4 polymer chain self-assembly; solvent characteristics can quickly change fast from "good" to "poor" due to decreased temperature or changes in the ratio between solvents in a mixed solvent approach due to rapid film solidification during processing.…”

Nanostructured Donor–Acceptor Self Assembly with Improved Photoconductivity

“…[1][2][3][4][5][6][7][8] Well-defined and reproducible nanoscale assemblies of donor-acceptor semiconducting materials are crucial for several devices in the optoelectronic applications. [1][2][3][4] From the perspective of device applications, it is highly desirable to translate the self-assembly of small molecules to processable polymers, which is a non-trivial task.…”