Effects of conjugated polymer incorporation on the morphology and energy harvesting of solution-processed, phthalocyanine-based thin films

Gary Z. Cheung, Binxing Yu, Mengdi Liu, Zheng Gong, Jesse Kohl, Christopher E. Petoukhoff, Piotr Piotrowiak, Deirdre M. O'Carroll

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Abstract

Here, we investigate the morphology, spectral absorption bandwidth and energy transfer in solution-processed, phthalocyanine-based thin films blended with conjugated polymer materials with complementary absorption bands. Unary, binary, and ternary solutions of the solution- processable phthalocyanine derivative 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine (Oct-Pc) and the conjugated polymers poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly(3-hexylthiophene) (P3HT) were used to prepare sub-55-nm-thick unary-phase and blended thin films. Spectroscopic analysis shows that absorption band full-width-at-half-maximum (FWHM) values increase from between 60 nm and 160 nm for the individual materials to greater than 450 nm for the composite ternary-blend thin film due to the complementary bandgap energies and spectral absorption bands of the constituent materials. Additionally, photoluminescence and transient absorption measurements show very efficient transfer of excited-state energy in the wider band-gap materials (donors) to the narrower band-gap material (acceptor). Resonant energy or charge transfer occurs with efficiencies between 90% and 100% for the various blends. Atomic-force microscopy and grazing-incidence, wide-angle X-ray scattering data indicate that P3HT and Oct-Pc exhibit the poorest blending. This correlates with the lowest donor photoluminescence quenching efficiency due to the extended separation of the P3HT chains from Oct-Pc molecules. However, addition of a relatively small fraction of PFO disrupts Oct-Pc crystallinity and enables improved mixing and energy transfer between P3HT and Oct-Pc.

Original languageEnglish
Pages (from-to)469-476
Number of pages8
JournalSynthetic Metals
Volume220
DOIs
Publication statusPublished - Oct 1 2016

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Keywords

  • Absorption
  • Morphology
  • Organic semiconductors
  • Photoluminescence
  • Ternary blend

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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