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Influence of solvent mixing on the morphology and performance of solar cells based on polyfluorene copolymer/fullerene blends

Zhang, FL ; Jespersen, Kim LU ; Bjorstrom, C ; Svensson, M ; Andersson, MR ; Sundström, Villy LU ; Magnusson, K ; Moons, E ; Yartsev, Arkady LU orcid and Inganas, O (2006) In Advanced Functional Materials 16(5). p.667-674
Abstract
The influence of the solvent on the morphology and performance of polymer solar cells is investigated ill devices based on blends of the polyfluorene copolymer, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-ben zothiadiazole)), and [6,6]-phenyl-C-61-butyric acid methyl ester. The blends are spin-coated from chloroform or from chloroform mixed with small amounts of xylene, toluene, or chlorobenzene. The devices are characterized under monochromatic light and solar illumination AM1.5 (AM: air mass). Ail enhancement of the photocurrent density is observed in diodes made from chloroform mixed with chlorobenzene, and reduced photocurrent density is observed in diodes made from chloroform mixed with xylene or toluene,... (More)
The influence of the solvent on the morphology and performance of polymer solar cells is investigated ill devices based on blends of the polyfluorene copolymer, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-ben zothiadiazole)), and [6,6]-phenyl-C-61-butyric acid methyl ester. The blends are spin-coated from chloroform or from chloroform mixed with small amounts of xylene, toluene, or chlorobenzene. The devices are characterized under monochromatic light and solar illumination AM1.5 (AM: air mass). Ail enhancement of the photocurrent density is observed in diodes made from chloroform mixed with chlorobenzene, and reduced photocurrent density is observed in diodes made from chloroform mixed with xylene or toluene, compared to diodes made from neat chloroform. The open-circuit voltages are almost the same in all diodes. The surfaces of the active layers are imaged using atomic force microscopy. Height images indicate that a finer and more uniform distribution of domains corresponds to the diodes with enhanced photocurrent that are made from chloroform mixed with chlorobenzene, while a structure with larger domains is associated with the lower photocurrents in the diodes made from chloroform mixed with xylene or toluene. The influence of the morphology on the excited-state dynamics and charge generation is investigated using time-resolved spectroscopy. Fast formation of bound charge pairs followed by their conversion into free charge carriers is resolved, and excitation-intensity-dependent non-geminate recombination of free charges is observed. A significant enhancement in free-charge-carrier generation is observed on introducing chlorobenzene into chloroform. Imaging photocurrent generation from the solar cells with a light-pulse technique shows an inhomogeneous photocurrent distribution, which is related to the undulations in the thickness of the active layer. Thicker parts of the diodes yield higher photocurrent values. (Less)
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author
; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Advanced Functional Materials
volume
16
issue
5
pages
667 - 674
publisher
Wiley-VCH Verlag
external identifiers
  • wos:000236555900009
  • scopus:33645327407
ISSN
1616-3028
DOI
10.1002/adfm.200500339
language
English
LU publication?
yes
additional info
The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060)
id
9a4fd70e-b9a6-4f42-873b-fc1fc33cb0da (old id 414678)
date added to LUP
2016-04-01 11:54:11
date last changed
2021-09-15 05:39:58
@article{9a4fd70e-b9a6-4f42-873b-fc1fc33cb0da,
  abstract     = {The influence of the solvent on the morphology and performance of polymer solar cells is investigated ill devices based on blends of the polyfluorene copolymer, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-ben zothiadiazole)), and [6,6]-phenyl-C-61-butyric acid methyl ester. The blends are spin-coated from chloroform or from chloroform mixed with small amounts of xylene, toluene, or chlorobenzene. The devices are characterized under monochromatic light and solar illumination AM1.5 (AM: air mass). Ail enhancement of the photocurrent density is observed in diodes made from chloroform mixed with chlorobenzene, and reduced photocurrent density is observed in diodes made from chloroform mixed with xylene or toluene, compared to diodes made from neat chloroform. The open-circuit voltages are almost the same in all diodes. The surfaces of the active layers are imaged using atomic force microscopy. Height images indicate that a finer and more uniform distribution of domains corresponds to the diodes with enhanced photocurrent that are made from chloroform mixed with chlorobenzene, while a structure with larger domains is associated with the lower photocurrents in the diodes made from chloroform mixed with xylene or toluene. The influence of the morphology on the excited-state dynamics and charge generation is investigated using time-resolved spectroscopy. Fast formation of bound charge pairs followed by their conversion into free charge carriers is resolved, and excitation-intensity-dependent non-geminate recombination of free charges is observed. A significant enhancement in free-charge-carrier generation is observed on introducing chlorobenzene into chloroform. Imaging photocurrent generation from the solar cells with a light-pulse technique shows an inhomogeneous photocurrent distribution, which is related to the undulations in the thickness of the active layer. Thicker parts of the diodes yield higher photocurrent values.},
  author       = {Zhang, FL and Jespersen, Kim and Bjorstrom, C and Svensson, M and Andersson, MR and Sundström, Villy and Magnusson, K and Moons, E and Yartsev, Arkady and Inganas, O},
  issn         = {1616-3028},
  language     = {eng},
  number       = {5},
  pages        = {667--674},
  publisher    = {Wiley-VCH Verlag},
  series       = {Advanced Functional Materials},
  title        = {Influence of solvent mixing on the morphology and performance of solar cells based on polyfluorene copolymer/fullerene blends},
  url          = {http://dx.doi.org/10.1002/adfm.200500339},
  doi          = {10.1002/adfm.200500339},
  volume       = {16},
  year         = {2006},
}