Subnanosecond charge recombination dynamics in P3HT/PC61BM films

Molecules. 2012 Nov 23;17(12):13923-36. doi: 10.3390/molecules171213923.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Absorptiometry, Photon
  • Fullerenes / chemistry*
  • Molecular Structure
  • Organoselenium Compounds / chemistry*
  • Polymers / chemistry
  • Semiconductors
  • Solar Energy
  • Solvents / chemistry

Substances

  • 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61
  • Fullerenes
  • Organoselenium Compounds
  • Polymers
  • Solvents
  • poly(3-hexyl)selenophene