Exitons in P3HT/SWNT/PCBM Heterojunctions

Semiconducting single walled carbon nanotubes (s-SWNT) are known for their high charge carrier transport. Thus, they are promising electron transporting materials for photovoltaic (PV) active layers of organic solar cells (OSCs). An increase in efficiency is found by adding s-SWNTs next to a donor (D) and acceptor (A) heterojunction such as P3HT and PCBM. Pump probe spectroscopy is used to follow the exciton dynamics through these active layers. However, such multi-component spectra are difficult to interpret. To disentangle the various processes, we use the triplet state of the system to model the evolution of the lowest energy s-SWNT excited state (E11). Specifically, using the electron (spin majority channel) and hole (spin minority channel) density distributions for the triplet state, we find where electrons and holes are transferred within the active layer. Further, applying a non-equilibrium Green's function (NEGF) approach, we obtain the rate of D to A charge transport