A Role of Side-Chain Regiochemistry of Thienylene–Vinylene–Thienylene (TVT) in the Transistor Performance of Isomeric Polymers

Abstract

The π-extended (E)-2-(2-(thiophen-2-yl)-vinyl)­thiophene (TVT)-based polymers are an interesting class of semiconducting polymers because of their excellent mobilities and unique film microstructures. Despite these properties, the effect of the side-chain regiochemistry of TVT skeletons on the intrinsic properties of these polymers remains unclear. To investigate this, in this study, hexyl-substituted TVT subunits with a “tail in (TI)” or “tail out (TO)” regiosymmetrical arrangement were first introduced into diketo­pyrrolopyrrole (DPP)-based copolymer main chains to afford “isomeric” polymers PI and PO, respectively. By combining optical spectroscopy, atomic force microscopy (AFM), and grazing incidence X-ray diffraction (GIXD) data, we quantitatively characterized the aggregation, crystallization, and backbone orientation of both polymer films, which were then correlated to the charge-carrier mobilities. The PI film exhibited a bimodal packing motif comprising a mixture of edge-on and face-on orientations, which was beneficial for three-dimensional (3D) charge transport and resulted in a hole mobility 2-fold larger than that in the PO film (μh = 1.69 cm2 V–1 s–1). This comparative study substantiates the important role of the regiochemistry of TVT in developing high-performance semiconducting polymers.

A Simple Phenyl Group Introduced at the Tail of Alkyl Side Chains of Small Molecular Acceptors: New Strategy to Balance the Crystallinity of Acceptors and Miscibility of Bulk Heterojunction Enabling Highly Efficient Organic Solar Cells

“…However, as pointed out above, the research of side chains of SMAs is monotonous and heavily dragged behind. Despite there have been tremendous and effective reports about the side chain modification of donor semiconductors, these results could be invalid even false in SMAs for their inherent distinction of molecular construction. For most of the donor materials, the main backbones were built by π–σ–π type with the electron‐rich, π‐spacers and electron‐deficient moieties connected by rotatable single bands.…”

The Effects of Side Chains on the Charge Mobilities and Functionalities of Semiconducting Conjugated Polymers beyond Solubilities

“…For certain conjugated polymers, the substitution positions of alkyl chains also influence the backbone coplanarity, electronic structure, interchain packing and thin film morphology, and accordingly the charge transporting performances are varied . Li and co‐workers investigated two conjugated polymers, i. e., P10 and P11 , in which the two alkyl chains attached to the bithiophene moiety are positioned differently ( Scheme ) .…”

“…In fact, P17 shows excellent performance in field‐effect transistors with hole mobilities up to 4.6 cm 2 V −1 s −1 (Figure a and Table ). The conjugated polymers P20 and P21 described by Yang and co‐workers also contain TVT moieties . They found that the positioning of two n ‐hexyl chains attached to the TVT moiety has a significant effect on the interchain packing and charge transporting behavior.…”

“…a) Reproduced with permission . Copyright 2014, American Chemical Society; b) Reproduced with permission . Copyright 2017, American Chemical Society.…”

Printing Semiconductor–Insulator Polymer Bilayers for High‐Performance Coplanar Field‐Effect Transistors

“…To further verify this vertical phase separation, we etched the film from the opposite direction of the film and obtained a similar result (Figure S3, Supporting Information). We subsequently used grazing incidence X‐ray diffraction (GIXRD) (Figure S4, Supporting Information), which is widely used for investigating molecular packing in organic thin films, to characterize the molecular self‐assembly of P3HT/PS film. It shows that π‐π packing direction of P3HT is along thin film plane, which is beneficial for the in‐plane charge transport.…”