title: Subnanosecond charge recombination dynamics in P3HT/PC61BM films.
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/PC(61)BM blend films. With reference to the CS(2)-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 (m(h)) and the bimolecular CR rate (γ(bi)) of the SVA films are μ(h) = 8.7 × 10(−4) cm2 × s(−1) × V(−1) and γ(bi) = 4.5 × 10(−10) cm3 × s(−1), whereas at Δt = 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.
authors.affiliation: Center for Condensed Matter Science and Technology, Department of Physics, Harbin Institute of Technology, Harbin 150001, China. zhang_wei_hit@126.com
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Ning-Jiu
authors.initials: NJ
authors.lastname: Zhao
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Huo
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Fu
authors.forename: Xi-Cheng
authors.initials: XC
authors.lastname: Ai
authors.forename: Jian-Ping
authors.initials: JP
authors.lastname: Zhang
mesh_terms: D015502:Absorptiometry, Photon; D037741:Fullerenes / Q000737:chemistry*; D015394:Molecular Structure; D016566:Organoselenium Compounds / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012666:Semiconductors; D012993:Solar Energy; D012997:Solvents / Q000737:chemistry
chemical_list: C551883:1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61; D037741:Fullerenes; D016566:Organoselenium Compounds; D011108:Polymers; D012997:Solvents; C526212:poly(3-hexyl)selenophene