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Title: Quantitative comparison of organic photovoltaic bulk heterojunction photostability under laser illumination

The photostability of bulk heterojunction organic photovoltaic films containing a polymer donor and a fullerene-derivative acceptor was examined using resonance Raman spectroscopy and controlled laser power densities. The polymer donors were poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT), or poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7). Four sample preparation methods were studied: (i) thin or (ii) thick films with fast solvent evaporation under nitrogen, (iii) thick films with slow solvent evaporation under nitrogen, and (iv) thin films dried under nitrogen followed by thermal annealing. Polymer order was assessed by monitoring a Raman peak’s full width at half-maximum and location as a function of illumination time and laser power densities from 2.5 × 103 to 2.5 × 105 W cm–2. Resonance Raman spectroscopy measurements show that before prolonged illumination, PCDTBT and PTB7 have the same initial order for all preparation conditions, while P3HT order improves with slow solvent drying or thermal annealing. All films exhibited changes to bulk heterojunction structure with 2.5 × 105 Wcm–2 laser illumination as measured by resonance Raman spectroscopy, and atomic force microscopy images show evidence of sample heating that affects the polymer over an area greater than the illumination profile. Furthermore, photostability data are important for proper characterization by techniques involving illumination and themore » development of devices suitable for real-world applications.« less
 [1] ;  [1] ;  [2] ;  [3] ;  [2] ;  [1]
  1. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
  2. Iowa State Univ., Ames, IA (United States)
  3. Iowa State Univ., Ames, IA (United States); Mansoura Univ., Mansoura (Egypt)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 1932-7447
Grant/Contract Number:
ECCS1055930; AC02-07CH11358; GM915
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 118; Journal Issue: 51; Journal ID: ISSN 1932-7447
American Chemical Society
Research Org:
Ames Lab. (AMES), Ames, IA (United States)
Sponsoring Org:
Country of Publication:
United States
resonance raman spectroscopy; thin films; P3HT; PCDTBT; PTB7