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The Performance-Determining Role of Lewis Bases in Dye-Sensitized Solar Cells Employing Copper-Bisphenanthroline Redox Mediators

Fürer, Sebastian O. ; Milhuisen, Rebecca A. ; Kashif, Muhammad K. ; Raga, Sonia R. ; Acharya, Shravan S. ; Forsyth, Craig ; Liu, Maning LU orcid ; Frazer, Laszlo ; Duffy, Noel W. and Ohlin, C. André , et al. (2020) In Advanced Energy Materials 10(37).
Abstract

Copper redox mediators have enabled open-circuit voltages (VOC) of over 1.0 V in dye-sensitized solar cells (DSCs) and have helped to establish DSCs as the most promising solar cell technology in low-light conditions. The addition of additives such as 4-tert-butylpyridine (tBP) to these electrolytes has helped in achieving high solar cell performances. However, emerging evidence suggests that tBP coordinates to the Cu(II) species and limits the performance of these electrolytes. To date, the implications of this coordination are poorly understood. Here, the importance of Lewis base additives for the successful implementation of copper complexes as redox mediators in DSCs is demonstrated. Two redox couples,... (More)

Copper redox mediators have enabled open-circuit voltages (VOC) of over 1.0 V in dye-sensitized solar cells (DSCs) and have helped to establish DSCs as the most promising solar cell technology in low-light conditions. The addition of additives such as 4-tert-butylpyridine (tBP) to these electrolytes has helped in achieving high solar cell performances. However, emerging evidence suggests that tBP coordinates to the Cu(II) species and limits the performance of these electrolytes. To date, the implications of this coordination are poorly understood. Here, the importance of Lewis base additives for the successful implementation of copper complexes as redox mediators in DSCs is demonstrated. Two redox couples, [Cu(dmp)2]+/2+ and [Cu(dpp)2]+/2+ (with dmp = 2,9-dimethyl-1,10-phenanthroline and dpp = 2,9-diphenyl-1,10-phenanthroline) in combination with three different Lewis bases, TFMP (4-(trifluoromethyl)pyridine), tBP, and NMBI (1-methyl-benzimidazole), are considered. Through single-crystal X-ray diffraction analysis, absorption, and 1H-NMR spectroscopies, the coordination of Lewis bases to the Cu(II) centers are studied. This coordination efficiently suppresses recombination losses and is crucial for high performing solar cells. If, however, the coordination involves a ligand exchange, as is the case for [Cu(dpp)2]+/2+, the redox mediator regeneration at the counter electrode is significantly retarded and the solar cells show current limitations.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
4-tert-butylpyridine, coordination, copper electrolyte, dye-sensitized solar cells, Lewis bases
in
Advanced Energy Materials
volume
10
issue
37
article number
2002067
publisher
Wiley-Blackwell
external identifiers
  • scopus:85090060691
ISSN
1614-6832
DOI
10.1002/aenm.202002067
language
English
LU publication?
no
id
b651e9b4-b76f-4a18-b0b6-c686d3ecd35e
date added to LUP
2023-08-24 12:30:45
date last changed
2025-04-04 15:06:23
@article{b651e9b4-b76f-4a18-b0b6-c686d3ecd35e,
  abstract     = {{<p>Copper redox mediators have enabled open-circuit voltages (V<sub>OC</sub>) of over 1.0 V in dye-sensitized solar cells (DSCs) and have helped to establish DSCs as the most promising solar cell technology in low-light conditions. The addition of additives such as 4-tert-butylpyridine (tBP) to these electrolytes has helped in achieving high solar cell performances. However, emerging evidence suggests that tBP coordinates to the Cu(II) species and limits the performance of these electrolytes. To date, the implications of this coordination are poorly understood. Here, the importance of Lewis base additives for the successful implementation of copper complexes as redox mediators in DSCs is demonstrated. Two redox couples, [Cu(dmp)<sub>2</sub>]<sup>+/2+</sup> and [Cu(dpp)<sub>2</sub>]<sup>+/2+</sup> (with dmp = 2,9-dimethyl-1,10-phenanthroline and dpp = 2,9-diphenyl-1,10-phenanthroline) in combination with three different Lewis bases, TFMP (4-(trifluoromethyl)pyridine), tBP, and NMBI (1-methyl-benzimidazole), are considered. Through single-crystal X-ray diffraction analysis, absorption, and <sup>1</sup>H-NMR spectroscopies, the coordination of Lewis bases to the Cu(II) centers are studied. This coordination efficiently suppresses recombination losses and is crucial for high performing solar cells. If, however, the coordination involves a ligand exchange, as is the case for [Cu(dpp)<sub>2</sub>]<sup>+/2+</sup>, the redox mediator regeneration at the counter electrode is significantly retarded and the solar cells show current limitations.</p>}},
  author       = {{Fürer, Sebastian O. and Milhuisen, Rebecca A. and Kashif, Muhammad K. and Raga, Sonia R. and Acharya, Shravan S. and Forsyth, Craig and Liu, Maning and Frazer, Laszlo and Duffy, Noel W. and Ohlin, C. André and Funston, Alison M. and Tachibana, Yasuhiro and Bach, Udo}},
  issn         = {{1614-6832}},
  keywords     = {{4-tert-butylpyridine; coordination; copper electrolyte; dye-sensitized solar cells; Lewis bases}},
  language     = {{eng}},
  month        = {{10}},
  number       = {{37}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Advanced Energy Materials}},
  title        = {{The Performance-Determining Role of Lewis Bases in Dye-Sensitized Solar Cells Employing Copper-Bisphenanthroline Redox Mediators}},
  url          = {{http://dx.doi.org/10.1002/aenm.202002067}},
  doi          = {{10.1002/aenm.202002067}},
  volume       = {{10}},
  year         = {{2020}},
}