Photoconductivity anisotropy study in uniaxially aligned polymer based planar photodiodes

Dhritiman Gupta, Thomas J.K. Brenner, Sebastian Albert-Seifried, Mi Jung Lee, Martin Heeney, Iain Mcculloch, Henning Sirringhaus*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


A study of photoconductivity in a planar photodiode based on the uniaxially aligned, semicrystalline polymer, poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3, 2-b]thiophene) (PBTTT) is presented. The charge carrier photogeneration yield in bulk conjugated polymers is usually low but it could possibly be enhanced by applying a sufficiently large electric field, particularly along the direction of the polymer backbone. PBTTT is, in principle, an ideal system to study any anisotropy in carrier photogeneration because directional alignment of fully extended polymer chains can be achieved over macroscopic length scales. However, we have found that electron trapping in this polymer results in high photoconductive gain obscuring measurements of intrinsic photogeneration. We study the mechanism of photoconductive gain using steady-state and transient photocurrent measurement. Constant background illumination and the deposition of a surface layer of an electron acceptor material have been found to be effective in reducing the gain effects.

Original languageEnglish (US)
Pages (from-to)36-42
Number of pages7
JournalOrganic Electronics
Issue number1
StatePublished - Jan 1 2012


  • Donor/acceptor bilayer
  • Photoconductive gain
  • Photoconductivity anisotropy
  • Transient response
  • Uniaxial polymer alignment

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering


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