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Title: Determination of active layer morphology in all-polymer photovoltaic cells

This paper investigates the structure of films spin-coated from blends of the semiconducting polymers poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly{2,6-[4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene]-alt-4,7(2,1,3-benzo­thiadiazole)} (PCPDTBT). Such blends are of potential use in all-polymer solar cells in which both the acceptor and the donor material generate excitons to contribute to the photocurrent. Prompted by threefold performance gains seen in polymer/fullerene and polymer blend solar cells upon addition of pristine graphene, devices are prepared from P3HT/PCPDTBT blends both with and without graphene. This report focuses on the morphology of the active layer since this is of critical importance in determining performance. Small-angle neutron scattering (SANS) is utilized to study this polymer blend with deuterated P3HT to provide contrast and permit the investigation of buried structure in neat and graphene-doped films. SANS reveals the presence of P3HT crystallites dispersed in an amorphous blend matrix of P3HT and PCPDTBT. The crystallites are approximately disc shaped and do not show any evidence of higher-order structure or aggregation. While the structure of the films does not change with the addition of graphene, there is a perceptible effect on the electronic properties and energy conversion efficiency in solar cells made from such films. Finally, determination of the active layer morphology yields crucial insightmore » into structure–property relationships in organic photovoltaic devices.« less
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  1. Univ. of Cincinnati, OH (United States). Biomedical, Chemical and Environmental Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Material Sciences
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biology and Soft Matter Division
  5. Univ. of Dayton Research Inst., Dayton, OH (United States). Nonstructural Materials Division
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Applied Crystallography (Online)
Additional Journal Information:
Journal Name: Journal of Applied Crystallography (Online); Journal Volume: 50; Journal Issue: 5; Journal ID: ISSN 1600-5767
International Union of Crystallography
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Cincinnati, OH (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; 14 SOLAR ENERGY; organic photovoltaics; small-angle scattering; graphene; morphology
OSTI Identifier: