Photo-induced electron transfer at nanostructured semiconductor–zinc porphyrin interface

Hakola, Hanna; Perros, Alexander Pyymaki; Myllyperkiö, Pasi; Kurotobi, Kei; Lipsanen, Harri; Imahori, Hiroshi; Lemmetyinen, Helge; Tkachenko, Nikolai V.

doi:10.1016/j.cplett.2013.11.028

Cited by 12 publications

(9 citation statements)

References 29 publications

(61 reference statements)

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“…Therefore, 1 can be considered as a good candidate for solar cell applications. However, it is important to pay attention to the time constant of the electron injection into ZnO, which is close to 5 ps and roughly one order in magnitude slower than that for a porphyrin on ZnO surface . Typical electron injection times for good sensitizers on TiO 2 are also much faster (0.1–2 ps). ,, Nevertheless, the 1 cation lifetime is rather long (>10 ns) and should be sufficient for the hole utilization by a suitable hole transporting material, e.g., spiro-MeOTAD.…”

Section: Discussionmentioning

confidence: 99%

“…This information would be gravely needed especially if the cell performance is not optimal. The photoinduced electron injection in phthalocyanine- or porphyrin-based DSSCs take place in the femto- to picosecond time scale, ,− and therefore, ultrafast spectroscopic methods are needed to analyze the reaction kinetics and to explain the reasons leading to differences in the performance in different solar cell designs.…”

Section: Introductionmentioning

confidence: 99%

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Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

et al. 2017

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Phthalocyanines (Pc) are well-known light-harvesting compounds. However, despite the tremendous efforts on phthalocyanine synthesis, the achieved energy conversion efficiencies for Pc-based dyesensitized solar cells are moderate. To cast light on the factors reducing the conversion efficiency, we have undertaken a time-resolved spectroscopy study of the primary photoinduced reactions at a semiconductor-Pc interface. ZnO nanorods were chosen as a model semiconductor substrate with enhanced specific surface area. The use of a nanostructured oxide surface allows to extend the semiconductor-dye interface with a hole transporting layer (spiro-MeOTAD) in a controlled way, making the studied system closer to a solid-state dye-sensitized solar cell. Four zinc phthalocyanines are compared in this study. The compounds are equipped with bulky peripheral groups designed to reduce the self-aggregation of the Pcs. Almost no signs of aggregation can be observed from the absorption spectra of the Pcs assembled on a ZnO surface. Nevertheless, the time-resolved spectroscopy indicates that there are inter-Pc charge separation−recombination processes in the time frame of 1−100 ps. This may reduce the electron injection efficiency into the ZnO by more than 50%, pointing out to a remaining aggregation effect. Surprisingly, the electron injection time does not correlate with the length of the linker connecting the Pc to ZnO. A correlation between the electron injection time and the "bulkiness" of the peripheral groups was observed. This correlation is further discussed with the use of computational modeling of the Pc arrangements on the ZnO surface.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

et al. 2017

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“…3,19,24,27,29 A comparison can be made with the results reported here, though we notice that most previously reported measurements were conducted with samples placed in a solution. It seems to be well accepted that the fastest electron injection from porphyrin to TiO 2 takes place for porphyrins a relatively short distance from the surface, e.g., provided by one phenyl spacer, and a slightly tilted orientation of the macrocycle.…”

Section: ■ Discussionmentioning

confidence: 78%

Photophysical Study of a Self-Assembled Donor–Acceptor Two-Layer Film on TiO₂

et al. 2015

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The self-assembled monolayer (SAM) technique was employed to fabricate a two-layer donor-acceptor film on the surface of TiO2. The approach is based on using donor and acceptor compounds with anchoring groups of different lengths. The acceptor, a fullerene derivative, has a carboxyl anchor attached to the fullerene moiety via a short linker that places the fullerene close to the surface. The donor, a porphyrin derivative, is equipped with a long linker that can penetrate between the fullerenes and keep porphyrin on top of the fullerene layer. The two-layer fullerene-porphyrin structures were deposited on a mesoporous film of TiO2 nanoparticles by immersing the TiO2 film sequentially into fullerene and porphyrin solutions. Transient absorption spectroscopy studies of the samples revealed that after the selective photoexcitation of porphyrin a fast (<5 ps) intermolecular electron transfer (ET) takes place from porphyrin to the fullerene layer, which confirms the formation of the interlayer donor-acceptor interface. Furthermore, in the second step of ET the fullerene anions donate electrons to the TiO2 nanoparticles. The latter reaction is relatively slow with an average time constant of 230 ps. It involves roughly half of the primary generated charges, and the second half relaxes by the interlayer charge recombination. The resulting state with a porphyrin cation and electron in TiO2 has an extremely long lifetime and recombines with an average time constant of 23 ms.

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“…This is rather fast CR. For example, the longest reported half times are >1 ns for porphyrin sensitizer , and much more than 1 ns for Ru-dyes . Rather fast CR at the TiO 2 |Pc interface is surprising and undesired result.…”

Section: Resultsmentioning

confidence: 99%

Effect of Co-Adsorbate and Hole Transporting Layer on the Photoinduced Charge Separation at the TiO₂–Phthalocyanine Interface

et al. 2018

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Understanding the primary processes of charge separation (CS) in solid-state dye-sensitized solar cells (DSSCs) and, in particular, analysis of the efficiency losses during these primary photoreactions is essential for designing new and efficient photosensitizers. Phthalocyanines (Pcs) are potentially interesting sensitizers having absorption in the red side of the optical spectrum and known to be efficient electron donors. However, the efficiencies of Pc-sensitized DSSCs are lower than that of the best DSSCs, which is commonly attributed to the aggregation tendency of Pcs. In this study, we employ ultrafast spectroscopy to discover why and how much does the aggregation affect the efficiency. The samples were prepared on a standard fluorine-doped tin oxide (FTO) substrates covered by a porous layer of TiO 2 nanoparticles, functionalized by a Pc sensitizer and filled by a hole transporting material (Spiro-MeOTAD). The study demonstrates that the aggregation can be suppressed gradually by using co-adsorbates, such as chenodeoxycholic acid (CDCA) and oleic acid, but rather high concentrations of co-adsorbate is required. Gradually, a few times improvement of quantum efficiency was observed at sensitizer/co-adsorbate ratio Pc/CDCA = 1:10 and higher. The time-resolved spectroscopy studies were complemented by standard photocurrent measurements of the same sample structures, which also confirmed gradual increase in photon-to-current conversion efficiency on mixing Pc with CDCA.

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Photo-induced electron transfer at nanostructured semiconductor–zinc porphyrin interface

Cited by 12 publications

References 29 publications

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Photophysical Study of a Self-Assembled Donor–Acceptor Two-Layer Film on TiO₂

Effect of Co-Adsorbate and Hole Transporting Layer on the Photoinduced Charge Separation at the TiO₂–Phthalocyanine Interface

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Photo-induced electron transfer at nanostructured semiconductor–zinc porphyrin interface

Cited by 12 publications

References 29 publications

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Photoinduced Electron Injection from Zinc Phthalocyanines into Zinc Oxide Nanorods: Aggregation Effects

Photophysical Study of a Self-Assembled Donor–Acceptor Two-Layer Film on TiO2

Effect of Co-Adsorbate and Hole Transporting Layer on the Photoinduced Charge Separation at the TiO2–Phthalocyanine Interface

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Product

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Photophysical Study of a Self-Assembled Donor–Acceptor Two-Layer Film on TiO₂

Effect of Co-Adsorbate and Hole Transporting Layer on the Photoinduced Charge Separation at the TiO₂–Phthalocyanine Interface