We report the direct and unambiguous determination of electron transfer rates and efficiencies from PbSe quantum dots (QDs) to mesoporous SnO2 films. We monitor the time-dependent electron density within the oxide with picosecond time resolution using Terahertz spectroscopy, following optical excitation of the QDs using a femtosecond laser pulse. QD-oxide electron transfer occurs with efficiencies of ∼2% in our samples under 800 nm pumping with a marked dependence on QD size, ranging from ∼100 ps injection times for the smallest, ∼2 nm diameter QDs, to ∼1 ns time scale for ∼7 nm QDs. The size-dependent electron transfer rates are modeled within the framework of Marcus theory and the implications of the results for device design are discussed.

Additional Metadata
Persistent URL dx.doi.org/10.1021/nl202550v
Journal Nano Lett.
Citation
Cánovas, E, Moll, P, Jensen, S.A, Gao, Y, Houtepen, A.J, Siebbeles, L.D.A, … Bonn, M. (2011). Size-dependent electron transfer from PbSe quantum dots to SnO2 monitored by picosecond Terahertz Spectroscopy. Nano Lett., 11(12), 5234–5239. doi:10.1021/nl202550v