Subpicosecond Photon-Energy-Dependent Hole Transfer from PbS Quantum Dots to Conjugated Polymers

作者：Colbert Adam E; Jedlicka Erin; Wu Wenbi; Ginger David S^*

来源：Journal of Physical Chemistry Letters, 2016, 7(24): 5150-5155.

DOI：10.1021/acs.jpclett.6b02490

We use transient absorption (TA) spectroscopy to study the origin of photon energy dependent hole transfer yields in blends of PbS quantum dots with the conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). We selectively excite only the quantum dots at two different wavelengths and measure the polymer ground state bleach resulting from the transfer of photoexcited holes. The higher photon-energy pump shows a greater prompt yield of hole transfer compared to the lower photon-energy excitation, on time scales sufficient to out-compete hot carrier cooling in lead chalcogenide quantum dots. We interpret the results as evidence that the excess energy of nonthermalized, or "hot," excitons resulting from higher photon-energy excitation allows more efficient charge transfer to the polymer in these systems. The data also demonstrate slow charge transfer rates, up to similar to 1 ns, of the relaxed excitations on the PbS dots. These findings help to clarify the role of excess photon energy and carrier relaxation dynamics on free carrier generation in donor/acceptor solar cells.

• 出版日期2016-12-15