Improved photoelectrochemical performance of electrodeposited ZnO/EosinY hybrid thin films by dye re-adsorption

Yoshida, Tsukasa; Iwaya, Mamiko; Ando, Hiroaki; Oekermann, Torsten; Nonomura, Kazuteru; Schlettwein, Derck; Wöhrle, Dieter; Minoura, Hideki

doi:10.1039/b312127e

Cited by 162 publications

(162 citation statements)

References 11 publications

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“…eosin Y, as structure-directing additives and subsequent removal of the dye by treatment with aqueous KOH. [9][10][11] Subsequent readsorption of another dye with a broad absorption band and a high absorption coefficient results in the formation of a sensitized ZnO electrode, which currently reaches efficiencies of up to 5.6% in DSSCs, with the added advantage that the low-temperature process opens up applications for flexible plastic-based devices. 12 For sensitization, metal-free dyes have come into the focus as an alternative for the frequently used ruthenium complexes.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films

Oum

Lohse

Flender

et al. 2012

Phys. Chem. Chem. Phys.

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The ultrafast photoinjection and subsequent relaxation steps of the indoline dye D149 were investigated in detail for a mesoporous electrodeposited ZnO thin film and compared with experiments on sintered TiO 2 and ZrO 2 thin films, all in contact with air, using pump-supercontinuum probe (PSCP) transient absorption spectroscopy in the range 370-770 nm. D149 efficiently injects electrons into the ZnO surface with time constants from r70 fs (time-resolution-limited) up to 250 fs, without the presence of slower components. Subsequent spectral dynamics with a time constant of 20 ps and no accompanying change in the oscillator strength are assigned to a transient Stark shift of the electronic absorption spectrum of D149 molecules in the electronic ground state due to the local electric field exerted by the D149 + radical cations and conduction band electrons in ZnO. This interpretation is consistent with the shape of the relaxed PSCP spectrum at long times, which resembles the first derivative of the inverted steady-state absorption spectrum of D149. In addition, steady-state difference absorption spectra of D149 + in solution from spectroelectrochemistry display a bleach band with distinctly different position, because no first-order Stark effect is present in that case. Interference features in the PSCP spectra probably arise from a change of the refractive index of ZnO caused by the injected electrons. The 20 ps component in the PSCP spectra is likely a manifestation of the transition from an initially formed bound D149 + -electron complex to isolated D149 + and mobile electrons in the ZnO conduction band (which changes the external electric field experienced by D149) and possibly also reorientational motion of D149 molecules in response to the electric field. We identify additional spectral dynamics on a similar timescale, arising from vibrational relaxation of D149 + by interactions with ZnO. TiO 2 exhibits similar dynamics to ZnO. In the case of ZrO 2 , electron injection accesses trap states, which exhibit a substantial probability for charge recombination. No Stark shift is observed in this case. In addition, the spectroelectrochemical experiments for D149 + in dichloromethane and acetonitrile, which cover the spectral range up to 2000 nm, provide for the first time access to its complete D 0 -D 1 absorption band, with the peak located at 1250 and 1055 nm, respectively. Good agreement is obtained with results from DFT/TDDFT calculations of the D149 + spectrum employing the MPW1K functional.

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Section: Introductionmentioning

confidence: 99%

Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films

Oum

Lohse

Flender

et al. 2012

Phys. Chem. Chem. Phys.

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“…7 Only a small number of sensitizers has yet been presented for ZnO that yield high quantum efficiencies but most of them have a narrow absorption spectrum leading to comparably low short-circuit photocurrent densities ( j sc ). [7][8][9][10] Another reason is that the photovoltage of most ZnO-based devices is limited by the typically used kinetically favorable but energetically unfavorable I − /I 3 − redox couple. 7 For TiO 2 -based DSSCs this shuttle has been replaced in the highly efficient cells by metal complexes that require a lower overvoltage for dye regeneration and whose redox potential is better adjusted to the semiconductor conduction band edge and the sensitizer HOMO z E-mail: schlettwein@uni-giessen.de energy level ( Figure 1).…”

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confidence: 99%

Metal Complexes as Redox Shuttles in Dye-Sensitized Solar Cells Based on Electrodeposited ZnO: Tuning Recombination Kinetics and Conduction Band Energy

Rueß

Nguyen

Schlettwein

2018

J. Electrochem. Soc.

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In this work, a pathway to engineer both interfacial charge recombination kinetics and conduction band energy in dye-sensitized solar cells based on mesoporous electrodeposited ZnO is presented. Especially in solar cells employing metal complex redox shuttles such as Co(bpy) 3 [bpy = 2,2'-bipyridine] and Cu(tmby) 2 [tmby = 4,4',6,6'-tetramethyl-2,2'-bipyridine] these factors are crucial in order to obtain efficient devices. Controlling them is achieved by augmenting the liquid redox electrolyte with additives. The most commonly used additive 4-tert-butylpyridine (TBP) induces both an upward shift of the ZnO conduction band energy and retards recombination thus leading to higher device performance. However, the full potential of the cells cannot be exploited by TBP since high concentrations lead to unwanted side reactions. However, adding another additive such as 2,2'-bipyridine or neocuproine can circumvent these problems and opens a full range of options to tune the properties of the ZnO/electrolyte interface. Photoelectrochemical techniques, such as impedance spectroscopy, current-voltage characterization and photocurrent transient measurements are utilized to reveal the underlying mechanisms of the different additives. Using these additives, power-conversionefficiencies of 3.56% for a Co(bpy) 3 -based electrolyte and 3.85% for a Cu(tmby) 2 -based electrolyte are achieved for electrodeposited ZnO sensitized with the organic dye DN216. Dye-sensitized solar cells (DSSCs) are receiving continued interest as photovoltaic devices because they can be fabricated with low preparation expenses, 1,2 with solar-to-electrical power conversion efficiencies (PC Es) up to 14.3% under one sun illumination.3 Thereby they offer options with low energy payback times for a sustainable photovoltaic technology on a very large scale, or, at least for niche applications. In such cells, light is absorbed by dye molecules that are adsorbed to a mesoporous semiconductor. Following light absorption, the dye injects excited electrons into the conduction band of the semiconductor from where they are transported to the front contact. Then the oxidized dye molecules are regenerated by a redox mediator that, on the other hand, is regenerated by the counter electrode at the back contact. 4 Highest PC E is achieved by using nanoparticulate TiO 2 as semiconductor which has to undergo high-temperature treatments of about 400• C to ensure high electron collection efficiency. 5This treatment limits the applicability of DSSCs, since it increases the required energy input and also prevents the use of polymer foils as substrate material. In order to circumvent such high-temperature processes, ZnO has been applied as porous semiconductor because a well-connected network can be directly grown by electrodeposition from aqueous solutions at a typical process temperature of 70However, the PC E of ZnO-based DSSCs is inferior compared to TiO 2 -based cells. One of the reasons is the low quantum efficiency when ZnO is sensitized with dyes that were optimized ...

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“…La máxima eficiencia hasta el momento para las películas híbridas de ZnO/Eoisn-Y aplicadas en DSSC ha sido 2.3 % [12] teniendo en cuenta la similitud de los niveles de energía que existen entre el ZnO y el Eosin-Y. Se pude apreciar, un exceso a la respuesta de fotocorriente por la incidencia de luz que se asocia a la baja reacción de generación de las moléculas oxidadas seguida por la inyección del ZnO, causado generalmente por la no-exposición a la luz, debido al enmascaramiento que genera el electrolito.…”

Section: E Análisis De La Respuesta De Fotocorrienteunclassified

Fabricación y caracterización de nano-estructuras de ZnO, y películas híbridas DE ZnO/EOSIN-Y para la conversión de energía

Moya

Socucase

García³

2013

Ingenium Rev. fac. ing.

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ResumenLa viabilidad de utilizar la técnica de electrodeposición catódica para la preparación de nuevos materiales híbridos porosos ha sido probada en este artículo. Se prepararon películas finas híbridas de ZnO utilizando compuestos orgánicos como la Eosin-Y. La morfología y la porosidad de las películas híbridas de ZnO son altamente dependientes de la concentración de colorante que es utilizado. Fue observada una alta sensibilidad para las películas de ZnO/Eosin-Y mediante la excitación de los electrones de los niveles de * Doctor en

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Improved photoelectrochemical performance of electrodeposited ZnO/EosinY hybrid thin films by dye re-adsorption

Abstract: Dye desorption and re-adsorption post treatments on electrochemically self-assembled nanoporous ZnO/eosinY hybrid thin films lead to a large improvement of the dye-sensitized photoelectrochemical performance, achieving an incident photon to current conversion efficiency up to 90%.

Cited by 162 publications

References 11 publications

Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films

Ultrafast dynamics of the indoline dye D149 on electrodeposited ZnO and sintered ZrO2 and TiO2 thin films

Metal Complexes as Redox Shuttles in Dye-Sensitized Solar Cells Based on Electrodeposited ZnO: Tuning Recombination Kinetics and Conduction Band Energy

Fabricación y caracterización de nano-estructuras de ZnO, y películas híbridas DE ZnO/EOSIN-Y para la conversión de energía

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