The Polymer Physics of Multiscale Charge Transport in Conjugated Systems

Abstract

Conjugated polymers are promising candidates for next‐generation low‐cost flexible electronics. Field‐effect transistors comprising conjugated polymers have witnessed significant improvements in device performance, notably the field‐effect mobility, in the last three decades. However, to truly make these materials commercially competitive, a better understanding of charge‐transport mechanisms in these structurally heterogeneous systems is needed for providing systematic guides for further improvements. This review assesses the key microstructural features of conjugated polymers across multiple length scales that can influence charge transport, with special attention given to the underlying polymer physics. The mechanistic understanding from collective experimental and theoretical studies point to the importance of interconnected ordered domains given the macromolecular nature of the polymeric semiconductors. Based on the criterion, optimization to improve charge transport can be broadly characterized by efforts to (a) promote intrachain transport, (b) establish intercrystallite connectivity, and (c) enhance interchain coupling. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1559–1571

The Role of Tie Chains on the Mechano‐Electrical Properties of Semiconducting Polymer Films

“…This observation further highlights the importance of intercrystallite connectivity, without which isolated crystallites would less likely contribute to in-plane macroscopic charge transport. [14,18,41] Supporting this position are our results with P3HT_5, which does not possess sufficient tie chains to support percolation, and its neighboring crystallites in essence isolated from one another. In the absence of intercrystallite connectivity, straining P3HT_5 does not induce any significant reorientation of the crystallites.…”

Processable High Electron Mobility π‐Copolymers via Mesoscale Backbone Conformational Ordering

“…[ 10 ] Second, the longer persistence‐lengths of chains emanating from rigid polymer aggregates are correlated with increased alignment of the tie chains spanning aggregates and fewer disordered chain entanglement interactions in intraaggregate regions. [ 52 ] Furthermore, the expansive self‐aligned mesoscale order of P4 and “edge‐on” packing mode with π–π order of ≈17 π‐stacked units are properties associated with ideal chain planarity and extension. Recall the UV–vis vibronic structure and π–π d‐spacings (Figure 4, Table 3) indicate that P4 backbones assume virtually ideal backbone planarity in contrast to P3.…”

Impact of sterilization on a conjugated polymer based bioelectronic patch

“…Chain scission and crosslinking will cause the conjugation length of the polymer to be reduced, hindering intra-and interchain transport and thus accounting for the drop in electrical properties. 49 Decrease in electric properties in response to γ-irradiation at doses ranging from 5 to 10 3 kGy have been reported for drop-casted polyaniline on a polyester substrate 48 and spin coated polyaniline films. 50 Of note, the electric properties were shown to deteriorate if γ-irradiation occurs in air due to oxidation of the film surface 48 .…”