Abstract
A series of bis-tridentate ruthenium complexes was designed to feature opposite localizations of their lowest metal-to-ligand charge transfer (MLCT) excited states, relative to a carboxylic acid that served as binding group to mesoporous NiO. The purpose was to study the effiect of MLCT direction on the rates of hole injection into NiO and subsequent charge recombination. Surprisingly, fs-transient absorption spectroscopy showed that the two heteroleptic, cyclometalated complexes of this series did not inject holes into NiO, but their excited states were nevertheless quenched in a rapid process (on the time scale of hundreds of picoseconds). An identical result was obtained for the dyes on non-reactive ZrO2 and we therefore attribute the short MLCT lifetime to self-quenching, due the high surface concentrations of the dyes. We further show that self-quenching on this time scale can potentially compete with hole injection also for functional NiO sensitizers. A ruthenium polypyridine complex, which has previously been used for NiO-based solar cells, was shown to inject holes only very slowly (τ ≈ 5 ns), in contrast to the common notion that hole injection in dye NiO systems is ultrafast (predominantly sub-ps time scale). The hole injection yield was estimated to only ca. 20 %, which matches the reported APCE value of the corresponding device [Freys, J. C.; Gardner, J. M.; D'Amario, L.; Brown, A. M.; Hammarström, L., Dalton Trans. 2012, 41,pp. 13105]. Therefore, we suggest that self-quenching and slow injection might be a reason for the low photovoltaic performance of some p-type dye-sensitized solar cells.
| Original language | English |
|---|---|
| Journal | Journal of Physical Chemistry C |
| DOIs | |
| Publication status | Accepted/In press - Jan 29 2018 |
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ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Energy(all)
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
Cite this
Self-Quenching and Slow Hole Injection May Limit the Efficiency in NiO-Based Dye-Sensitized Solar Cells. / Föhlinger, Jens; Maji, Somnath; Brown, Allison M.; Mijangos, Edgar; Ott, Sascha; Hammarström, Leif.
In: Journal of Physical Chemistry C, 29.01.2018.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Self-Quenching and Slow Hole Injection May Limit the Efficiency in NiO-Based Dye-Sensitized Solar Cells
AU - Föhlinger, Jens
AU - Maji, Somnath
AU - Brown, Allison M.
AU - Mijangos, Edgar
AU - Ott, Sascha
AU - Hammarström, Leif
PY - 2018/1/29
Y1 - 2018/1/29
N2 - A series of bis-tridentate ruthenium complexes was designed to feature opposite localizations of their lowest metal-to-ligand charge transfer (MLCT) excited states, relative to a carboxylic acid that served as binding group to mesoporous NiO. The purpose was to study the effiect of MLCT direction on the rates of hole injection into NiO and subsequent charge recombination. Surprisingly, fs-transient absorption spectroscopy showed that the two heteroleptic, cyclometalated complexes of this series did not inject holes into NiO, but their excited states were nevertheless quenched in a rapid process (on the time scale of hundreds of picoseconds). An identical result was obtained for the dyes on non-reactive ZrO2 and we therefore attribute the short MLCT lifetime to self-quenching, due the high surface concentrations of the dyes. We further show that self-quenching on this time scale can potentially compete with hole injection also for functional NiO sensitizers. A ruthenium polypyridine complex, which has previously been used for NiO-based solar cells, was shown to inject holes only very slowly (τ ≈ 5 ns), in contrast to the common notion that hole injection in dye NiO systems is ultrafast (predominantly sub-ps time scale). The hole injection yield was estimated to only ca. 20 %, which matches the reported APCE value of the corresponding device [Freys, J. C.; Gardner, J. M.; D'Amario, L.; Brown, A. M.; Hammarström, L., Dalton Trans. 2012, 41,pp. 13105]. Therefore, we suggest that self-quenching and slow injection might be a reason for the low photovoltaic performance of some p-type dye-sensitized solar cells.
AB - A series of bis-tridentate ruthenium complexes was designed to feature opposite localizations of their lowest metal-to-ligand charge transfer (MLCT) excited states, relative to a carboxylic acid that served as binding group to mesoporous NiO. The purpose was to study the effiect of MLCT direction on the rates of hole injection into NiO and subsequent charge recombination. Surprisingly, fs-transient absorption spectroscopy showed that the two heteroleptic, cyclometalated complexes of this series did not inject holes into NiO, but their excited states were nevertheless quenched in a rapid process (on the time scale of hundreds of picoseconds). An identical result was obtained for the dyes on non-reactive ZrO2 and we therefore attribute the short MLCT lifetime to self-quenching, due the high surface concentrations of the dyes. We further show that self-quenching on this time scale can potentially compete with hole injection also for functional NiO sensitizers. A ruthenium polypyridine complex, which has previously been used for NiO-based solar cells, was shown to inject holes only very slowly (τ ≈ 5 ns), in contrast to the common notion that hole injection in dye NiO systems is ultrafast (predominantly sub-ps time scale). The hole injection yield was estimated to only ca. 20 %, which matches the reported APCE value of the corresponding device [Freys, J. C.; Gardner, J. M.; D'Amario, L.; Brown, A. M.; Hammarström, L., Dalton Trans. 2012, 41,pp. 13105]. Therefore, we suggest that self-quenching and slow injection might be a reason for the low photovoltaic performance of some p-type dye-sensitized solar cells.
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U2 - 10.1021/acs.jpcc.8b01016
DO - 10.1021/acs.jpcc.8b01016
M3 - Article
AN - SCOPUS:85046670221
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
ER -