Electrical characterization of single-walled carbon nanotubes in organic solar cells by Kelvin probe force microscopy

The electrical role (donor or acceptor) of single-walled carbon nanotubes (SWCNTs) in organic solar cells remains controversial in the literature. Using Kelvin probe force microscopy (KPFM) to investigate SWCNTs on regioregular poly 3-hexylthiophene (P3HT) film as well as on P3HT and methanofullerene blended film, we have observed that photoinduced holes transport from active layer to SWCNTs, which indicates that SWCNTs work as donor materials. Moreover, KPFM study of SWCNTs on P3HT film reveals that the relatively low power conversion efficiency of P3HT/SWCNTs solar cells is attributed to deficient photoexcited carrier transport between P3HT and SWCNTs because of inefficient exciton dissociation.