Supramolecular cocrystals built through redox-triggered ion intercalation in π-conjugated polymers

Molecular doping of pi-conjugated semiconducting polymers can increase charge carrier density. Here, guest dopants are found to locate in the restricted void space in the lamellae, revealing an intercalated compound composed of layered polymer and guest intercalant. Self-organization in pi-conjugated polymers gives rise to a highly ordered lamellar structure, in which inter-chain stacking spontaneously forms two-dimensional conjugated sheets. This multi-layer stacked nature of semicrystalline polymers allows the inclusion of various functional molecules. In particular, redox-triggered ion-intercalation is an ideal system for molecular doping, for which extremely high charge carrier density has been achieved. Here, we conducted a detailed structural analysis and electron density simulation to pinpoint exactly where the guest dopants are located periodically in the void space in a polymer's lamellae. Our findings are indicative of an intercalation compound of layered polymers and a guest intercalant. We show that a homogeneous cocrystal structure can be realized throughout the host polymer medium, which is proved by the observation of coherent carrier transport. The intercalation cocrystal nature gives the best achievable doping level in semicrystalline polymers and excellent environmental stability. These findings should open up possibilities for tuning the collective dynamics of functional molecules through intercalation phenomena.

Automated summary

Molecular doping of pi-conjugated semiconducting polymers can increase charge carrier density by forming intercalated compounds composed of layered polymers and guest intercalants. The multi-layer stacked nature of semicrystalline polymers allows the inclusion of various functional molecules. Intercalation cocrystal nature gives the best achievable doping level in semicrystalline polymers and excellent environmental stability.