Organic electronic materials have the potential to impact almost every aspect of modern life including how we access information, light our homes, and power personal electronics. Nevertheless, weak intermolecular interactions and disorder at junctions of different organic materials limit the performance and stability of organic interfaces and hence the applicability of organic semiconductors to electronic devices. Here, we demonstrate control of donor-acceptor heterojunctions through microphase-separated conjugated block copolymers. When utilized as the active layer of photovoltaic cells, block copolymer-based devices demonstrate efficient photoconversion well beyond devices composed of homopolymer blends. The 3% block copolymer device efficiencies are achieved without the use of a fullerene acceptor. X-ray scattering results reveal that the remarkable performance of block copolymer solar cells is due to self-assembly into mesoscale lamellar morphologies with primarily face-on crystallite orientations. Conjugated block copolymers thus provide a pathway to enhance performance in excitonic solar cells through control of donor-acceptor interfaces.

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Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.

Conjugated block copolymers have the potential to improve solution processed optoelectronic devices such as organic photovoltaics (OPVs), but significant synthetic challenges exist and systematic studies investigating structure− property relationships are lacking. We demonstrate a new route to conjugated block copolymers via copper-catalyzed click coupling and apply this method to synthesize a series of poly(3-hexylthiophene)-block-poly(9,9-dioctylfluorene) (P3HT-b-PF) conjugated block copolymers with varying block weight fractions. The resulting block copolymers are comprised of two conjugated polymers joined by a flexible, nonconjugated linker. The series of conjugated block copolymers prepared enables an investigation into the role of polymer block lengths and composition on crystallization and self-assembly behavior. Grazing incidence wide-angle X-ray scattering measurements indicate the formation of highly oriented P3HT and/or PF crystallites in thermally annealed block copolymer films. Crystallization of either P3HT or PF blocks is predominant in all block copolymers studied, but at intermediate ratios crystallization of both blocks is observed.