Photoinduced Energy and Charge Transfer in P3HT:SWNT Composites

Using steady-state photoluminescence and transient microwave conductivity (TRMC) spectroscopies, photoinduced energy and charge transfer from poly(3-hexylthiophene) (P3HT) to single-walled carbon nanotubes (SWNTs) are reported. Long-lived charge carriers are observed for excitons generated in the polymer due to interfacial electron transfer, while excitation of the SWNTs results in short-lived carriers confined to the nanotubes. The TRMC-measured mobility of electrons injected into the SWNTs exhibits a surprisingly small lower limit of 0.057 cm²/(V s), which we attribute to carrier scattering within the nanotube that inhibits resonance of the microwave electric field with the confined carriers. The observation of charge transfer and the lifetime of the separated carriers suggest that the primary photoinduced carrier generation process does not limit the performance of organic photovoltaic (OPV) devices based on P3HT:SWNT composites. With optimization, blends of P3HT with semiconducting SWNTs (s-SWNTs) may exhibit promise as an OPV active layer and could provide good solar photoconversion power efficiencies.