Regioregular narrow-bandgap-conjugated polymers for plastic electronics

C onjugated polymers are characterized by an electronically delocalized p-conjugated backbone. This broad class of materials has attracted considerable attention from both industrial and academic research communities due to their potential to manufacture large-area and flexible organic electronic devices via low-cost solution processing techniques1–4. Remarkable progress has been achieved towards their integration into organic light-emitting diodes5–8, organic solar cells9–12, organic field-effect transistors (OFETs)13–16 and chemical or biological sensors17,18. A key consideration in the design of their overall molecular structure concerns how to optimize both the p-conjugated framework, relevant for optoelectronic function, and the side groups, which are needed for solubility, but which may also decrease morphological order in the solid state and thereby impact charge carrier transport. A delicate balance of the two structural components is required to achieve properties desirable for device function and a sufficiently high solubility for enabling straightforward processing options19,20. Higher levels of morphological order in the solid state are more easily achieved when there is translational symmetry between repeat units, or substructures that comprise a number of repeat units, along the backbone vector21–23. When the repeat units in the backbone are asymmetric, which may be a result of the intrinsic geometry of the fragments that contribute to electronic delocalization or from the substitution pattern of the solubilizing groups, a fine control over their organization in the chain is needed, see Box 1. Indeed, the level of organization at the single chain level impacts the electronic coupling, secondary structure of the chain, solid-state microstructure and transport of the charge carriers in the solid state24. DOI: 10.1038/ncomms14047 OPEN