Effects of branching position of alkyl side chains on ordering structure and charge transport property in thienothiophenedione- and quinacridone-based semiconducting polymers

Abstract

To investigate the effect of the branching position of the alkyl groups on the side chain of semiconducting polymers, we synthesized two series of semiconducting polymers based on thienothiophene-2,5-dione (PTTD4Ts) and quinacridone (PQA2Ts). 2-Decyltetradecyl, 3-decylpentadecyl, 4-decylhexadecyl, and 5-decylheptadecyl groups were used, and the branching position was systematically varied from the second carbon from the backbone to the fifth carbon. These branched side chains are introduced into the thiophene ring for PTTD4Ts and the quinacridone unit for PQA2Ts. The polymer thin films exhibited small but clear differences in their optical absorption spectra, suggesting that the intermolecular interaction in the solid state varied based on the branching position. The grazing incident X-ray diffraction study revealed that the π-π stacking d-spacing of both polymers decreased when the branching position was moved away from the backbones, indicating that the intermolecular interaction was enhanced. Therefore, regardless of the core where the alkyl groups were introduced, the branching position effectively improved the ordering structure of the polymers, which was most likely due to suppressed steric hindrance. Although PTTD4Ts did not exhibit a clear correlation between the branching position and charge carrier mobility, the mobility of PQA2Ts gradually increased as the branching position moved away from the backbone.

A Quinacridone-Diphenylquinoxaline-Based Copolymer for Organic Field-Effect Transistors

“…A comparison of the crystalline structures of PQCQT and PQCTQx in film state revealed that the crystalline structure of PQCTQx was not as good as that of PQCQT for charge transport in OFET devices [17,18]. Because the diphenylquinoxaline unit in PQCTQx is in bulky groups and generates steric hindrance, edge-on arrangement may become difficult [19,20]. Increasing the annealing temperature by an additional 50 °C yielded decreased intensities of the observed peaks along both (100) and (010) directions.…”

The Effect of α‐Branched Side Chains on the Structural and Opto‐Electronic Properties of Poly(Diketopyrrolopyrrole‐alt‐Terthiophene)

“…However, this is not always coupled to an increased charge carrier mobility as measured in organic field‐effect transistors. The alkyl chain can also influence the preferred orientation (edge‐on versus face‐on) of the π‐conjugated main chain with respect to the substrate after depositing the polymers from solution [6, 7, 9] …”

Linear-type carbazoledioxazine-based organic semiconductors: the effect of backbone planarity on the molecular orientation and charge transport properties

“…With their interesting optical and electrical properties, organic semiconductors are increasingly prominent in various electronic devices such as organic photovoltaics (OPVs) [1][2][3][4][5][6][7][8][9] and organic thin lm transistors (TFTs). [10][11][12][13][14][15][16][17][18] In particular, due to their solution processability and mechanical exibility, organic semiconductors would become fundamental components for novel mobile electronic devices, such as exible displays, biocompatible sensors, and radio frequency identication (RFID) tags. [19][20][21] In order to realize such next-generation devices, signicant efforts have been devoted to the development of new organic semiconducting materials, some of which already demonstrated charge carrier mobilities beyond the benchmark of industry standard inorganic materials, such as amorphous silicon (0.1-1 cm 2 V À1 s À1 ).…”