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Molecules 2012, 17(12), 13923-13936; doi:10.3390/molecules171213923
Article

Subnanosecond Charge Recombination Dynamics in P3HT/PC61BM Films

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1 Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001, China 2 Department of Chemistry, Renmin University of China, Beijing 100872, China
* Author to whom correspondence should be addressed.
Received: 25 October 2012 / Revised: 9 November 2012 / Accepted: 16 November 2012 / Published: 23 November 2012
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Abstract

Ultrafast near-infrared absorption spectroscopy was used to investigate the influence of film morphology and excitation photon energy on the charge recombination (CR) dynamics in the initial nanosecond timescale in the P3HT/PC61BM blend films. With reference to the CS2-cast films, the solvent vapor annealed (SVA) ones show 2–3-fold improvement in hole mobility and more than 5-fold reduction in the polymer-localized trap states of holes. At Dt = 70 ps, the hole mobility (mh) and the bimolecular CR rate (gbi) of the SVA films are mh = 8.7 × 10−4 cm2×s−1×V−1 and gbi = 4.5 × 10−10 cm3×s−1, whereas at Dt = 1 ns they drop to 8.7 × 10−5 cm2×s−1×V−1 and 4.6 × 10−11 cm3×s−1, respectively. In addition, upon increasing the hole concentration, the hole mobility increases substantially faster under the above-gap photoexcitation than it does under the band-gap photoexcitation, irrespective of the film morphologies. The results point to the importance of utilizing the photogenerated free charges in the early timescales.
Keywords: [6,6]-phenyl-C61-butyric acid methyl ester (PCBM); poly(3-hexylthiophene) (P3HT); solvent vapor annealing (SVA); time-resolved spectroscopy; bimolecular charge recombination; trap states [6,6]-phenyl-C61-butyric acid methyl ester (PCBM); poly(3-hexylthiophene) (P3HT); solvent vapor annealing (SVA); time-resolved spectroscopy; bimolecular charge recombination; trap states
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Zhang, W.; Zhao, N.-J.; Huo, M.-M.; Fu, L.-M.; Ai, X.-C.; Zhang, J.-P. Subnanosecond Charge Recombination Dynamics in P3HT/PC61BM Films. Molecules 2012, 17, 13923-13936.

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