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
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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.
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(12):13923-13936.
Zhang, Wei; Zhao, Ning-Jiu; Huo, Ming-Ming; Fu, Li-Min; Ai, Xi-Cheng; Zhang, Jian-Ping. 2012. "Subnanosecond Charge Recombination Dynamics in P3HT/PC61BM Films." Molecules 17, no. 12: 13923-13936.