Dissociating excitons photogenerated in semiconducting carbon nanotubes at polymeric photovoltaic heterojunction interfaces.

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have strong near-infrared and visible absorptivity and exceptional charge transport characteristics, rendering them highly attractive semiconductor absorbers for photovoltaic and photodetector technologies. However, these applications are limited by a poor understanding of how photogenerated charges, which are bound as excitons in s-SWCNTs, can be dissociated in large-area solid-state devices. Here, we measure the dissociation of excitons in s-SWCNT thin films that form planar heterojunction interfaces with polymeric photovoltaic materials using an exciton dissociation-sensitive photocapacitor measurement technique that is advantageously insensitive to optically induced thermal photoconductive effects. We find that fullerene and polythiophene derivatives induce exciton dissociation, resulting in electron and hole transfer, respectively, away from optically excited s-SWCNTs. Significantly weaker or no charge transfer is observed using wider gap polymers due to insufficient energy offsets. These results are expected to critically guide the development of thin film s-SWCNT-based photosensitive devices.