Influence of Branched Alkyl Ester-Labeled Side Chains on Specific Chain Arrangement and Charge-Transport Properties of Diketopyrrolopyrrole-Based Conjugated Polymers

Abstract

A series of diketopyrrolopyrrole (DPP)-based copolymers, with DPP and bithiophene (BT) as the electron-acceptor and donor backbone units, respectively, are synthesized with branched alkyl side chains that are either directly coupled to the N-positions of DPP or separated by an alkyl ester group. The ester moieties in the side chains induce specific cohesive molecular interactions between these side chains, as compared to the alkyl-only side chains with weak van der Waals interactions. Structure analysis of the DPPBT-based copolymers demonstrated that the introduction of a proper alkyl ester spacer to the branched alkyl chains can shorten the π–π stacking distance between the DPPBT backbones down to 3.61 Å and promote the development of two-dimensionally extended domains. DPPBT-based copolymers, including different branched alkyl ester-labeled side chains, are spun-cast on polymer-treated SiO2 dielectrics from dilute chloroform solutions for organic thin-film transistors. A DPPBT-based copolymer with properly engineered side chains (i.e., 2-decyltetradecyl ester-labeled side chains) shows the highest hole mobility of 2.30 cm2 V–1 s–1 and an on/off current ratio of above 106.

Spontaneous Phase Separation of Poly(3‐hexylthiophene)s with Different Regioregularity for a Stretchable Semiconducting Film

“…Values of µ and threshold voltage ( V th ) were calculated using the following equation: I D = µ C i ( W /2 L ) ( V G − V th ) 2 , where I D is the drain current, and V G and C i are the gate voltage and capacitance of the dielectrics, respectively. The C i value of the polymer‐treated SiO 2 dielectrics was ≈10.8 nF cm −2 …”

Incorporation of hydrogen‐bonding units into polymeric semiconductors toward boosting charge mobility, intrinsic stretchability, and self‐healing ability

“…Kim et al 58 reported a series of DPP based conjugated polymers with side chains containing ester groups (Figure 3). They found that H‐bond between the O atom of ester carbonyl and the H atom of alkyl could not only promote the π‐π stacking of polymer backbone but also expand the domain size in thin films.…”

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

“…The most commonly investigated branched side chains, have a branching point at the β‐carbon relative to the π‐conjugated backbone, or at a carbon atom further away. For several polymers, a shift of the branching point position away from the polymer backbone resulted in tighter π–π stacking [3, 5–8] . However, this is not always coupled to an increased charge carrier mobility as measured in organic field‐effect transistors.…”

“…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] …”