Two channels of charge generation in perylene monoimide solid-state dye-sensitized solar cells

I.A. Howard, M. Meister, B. Baumeier, H. Wonneberger, N. Pschirer, R. Sens, I. Bruder, C. Li, K. Müllen, D. Andrienko, F. Laquai

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Abstract

The mechanism of charge generation in solid-state dye-sensitized solar cells using triarylamine-substituted perylene monoimide dyes is studied by vis-NIR broadband pump-probe transient absorption spectroscopy. The experiments demonstrate that photoinduced electron injection into the TiO2 can only occur in regions where Li+, from the commonly used Li-TFSI additive salt, is present on the TiO2 surface. Incomplete surface coverage by Li+ means that some dye excitons cannot inject their electron into the TiO2. However it is observed in the solar cell structure that some of the dye excitons that cannot directly inject an electron still contribute to free charge generation by the previously hypothesized reductive quenching mechanism (hole transfer to the solid-state hole transporter followed by electron injection from the dye anion into the TiO2). The contribution of reductive quenching to the quantum efficiency of charge generation is significant, raising it from 68% to over 80%. Optimization of this reductive quenching pathway could be exploited to maintain high quantum efficiency in dyes with greater NIR absorption to achieve overall enhancements in device performance. It is demonstrated that broadband NIR transient spectroscopy is necessary to obtain population kinetics in these systems, as strong Stark effects distort the population kinetics in the visible region. Broadband ultrafast spectroscopy shows that electron injection into TiO 2 from a red absorbing organic dye can be enhanced by a process in which a hole is transferred to the hole transport material to allow injection from the anion state of the dye. Quantitative analysis suggests this mechanism accounts for ≈10% of the charges generated and could be further enhanced. The reductive quenching mechanism of charge generation contributes to photocurrent generation.

Original languageEnglish
Article number1300640
JournalAdvanced Energy Materials
Volume4
Issue number2
DOIs
Publication statusPublished - Jan 2014
Externally publishedYes

Fingerprint

Perylene
Coloring Agents
Dyes
Electron injection
Quenching
Quantum efficiency
Excitons
Anions
Negative ions
Spectroscopy
Stark effect
Kinetics
Electrons
Dye-sensitized solar cells
Photocurrents
Absorption spectroscopy
Solar cells
Salts
Pumps

Keywords

  • electronic processes
  • electronic structures
  • photochemistry
  • solar cells
  • titanium dioxide

Cite this

Howard, I.A. ; Meister, M. ; Baumeier, B. ; Wonneberger, H. ; Pschirer, N. ; Sens, R. ; Bruder, I. ; Li, C. ; Müllen, K. ; Andrienko, D. ; Laquai, F. / Two channels of charge generation in perylene monoimide solid-state dye-sensitized solar cells. In: Advanced Energy Materials. 2014 ; Vol. 4, No. 2.
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Howard, IA, Meister, M, Baumeier, B, Wonneberger, H, Pschirer, N, Sens, R, Bruder, I, Li, C, Müllen, K, Andrienko, D & Laquai, F 2014, 'Two channels of charge generation in perylene monoimide solid-state dye-sensitized solar cells', Advanced Energy Materials, vol. 4, no. 2, 1300640. https://doi.org/10.1002/aenm.201300640

Two channels of charge generation in perylene monoimide solid-state dye-sensitized solar cells. / Howard, I.A.; Meister, M.; Baumeier, B.; Wonneberger, H.; Pschirer, N.; Sens, R.; Bruder, I.; Li, C.; Müllen, K.; Andrienko, D.; Laquai, F.

In: Advanced Energy Materials, Vol. 4, No. 2, 1300640, 01.2014.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Two channels of charge generation in perylene monoimide solid-state dye-sensitized solar cells

AU - Howard, I.A.

AU - Meister, M.

AU - Baumeier, B.

AU - Wonneberger, H.

AU - Pschirer, N.

AU - Sens, R.

AU - Bruder, I.

AU - Li, C.

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AU - Andrienko, D.

AU - Laquai, F.

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N2 - The mechanism of charge generation in solid-state dye-sensitized solar cells using triarylamine-substituted perylene monoimide dyes is studied by vis-NIR broadband pump-probe transient absorption spectroscopy. The experiments demonstrate that photoinduced electron injection into the TiO2 can only occur in regions where Li+, from the commonly used Li-TFSI additive salt, is present on the TiO2 surface. Incomplete surface coverage by Li+ means that some dye excitons cannot inject their electron into the TiO2. However it is observed in the solar cell structure that some of the dye excitons that cannot directly inject an electron still contribute to free charge generation by the previously hypothesized reductive quenching mechanism (hole transfer to the solid-state hole transporter followed by electron injection from the dye anion into the TiO2). The contribution of reductive quenching to the quantum efficiency of charge generation is significant, raising it from 68% to over 80%. Optimization of this reductive quenching pathway could be exploited to maintain high quantum efficiency in dyes with greater NIR absorption to achieve overall enhancements in device performance. It is demonstrated that broadband NIR transient spectroscopy is necessary to obtain population kinetics in these systems, as strong Stark effects distort the population kinetics in the visible region. Broadband ultrafast spectroscopy shows that electron injection into TiO 2 from a red absorbing organic dye can be enhanced by a process in which a hole is transferred to the hole transport material to allow injection from the anion state of the dye. Quantitative analysis suggests this mechanism accounts for ≈10% of the charges generated and could be further enhanced. The reductive quenching mechanism of charge generation contributes to photocurrent generation.

AB - The mechanism of charge generation in solid-state dye-sensitized solar cells using triarylamine-substituted perylene monoimide dyes is studied by vis-NIR broadband pump-probe transient absorption spectroscopy. The experiments demonstrate that photoinduced electron injection into the TiO2 can only occur in regions where Li+, from the commonly used Li-TFSI additive salt, is present on the TiO2 surface. Incomplete surface coverage by Li+ means that some dye excitons cannot inject their electron into the TiO2. However it is observed in the solar cell structure that some of the dye excitons that cannot directly inject an electron still contribute to free charge generation by the previously hypothesized reductive quenching mechanism (hole transfer to the solid-state hole transporter followed by electron injection from the dye anion into the TiO2). The contribution of reductive quenching to the quantum efficiency of charge generation is significant, raising it from 68% to over 80%. Optimization of this reductive quenching pathway could be exploited to maintain high quantum efficiency in dyes with greater NIR absorption to achieve overall enhancements in device performance. It is demonstrated that broadband NIR transient spectroscopy is necessary to obtain population kinetics in these systems, as strong Stark effects distort the population kinetics in the visible region. Broadband ultrafast spectroscopy shows that electron injection into TiO 2 from a red absorbing organic dye can be enhanced by a process in which a hole is transferred to the hole transport material to allow injection from the anion state of the dye. Quantitative analysis suggests this mechanism accounts for ≈10% of the charges generated and could be further enhanced. The reductive quenching mechanism of charge generation contributes to photocurrent generation.

KW - electronic processes

KW - electronic structures

KW - photochemistry

KW - solar cells

KW - titanium dioxide

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