Determination of electron and hole energy levels in mesoporous nanocrystalline TiO2 solid-state dye solar cell

Garcı́a-Cañadas, Jorge; Fabregat‐Santiago, Francisco; Bolink, Henk J.; Palomares, Emilio; García-Belmonte, Germà; Bisquert, Juan

doi:10.1016/j.synthmet.2006.06.006

Cited by 66 publications

(51 citation statements)

References 23 publications

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“…The V oc corresponds to the energy difference between the quasi Fermi level (QFL, n E F ) of the electrons in the photoanode under illumination and the redox potential of the HTM. The higher V oc for the solid state HTM compared to the liquid electrolytes is expected between the liquid and solid-state devices because of the positive shift in the redox potential value of Spiro (0.818 V vs NHE, obtained from the cyclic voltammetry of Spiro-OMeTAD deposited onto ITO in propylene carbonate) [28][29] with respect to the standard redox potential of I À =I À 3 (0.530 V vs NHE), [30] If the conduction band position and trap states distribution in the TiO 2 nanoparticles remain the same [28][29][30] one would expect the V oc to increase by 288 mV. However, the photovoltage increase observed here was only 70-80 mV.…”

Section: Photovoltage Transient Decay Measurementsmentioning

confidence: 99%

“…A reasonable level for the TiO 2 conduction band edge of À4.05~À4.1 eV vs vacuum was assumed and the redox potential for the I À =I À 3 couple and Spiro are also included. [28][29][30]40] To show the Fermi level in the TiO 2 at the V oc , we added the V oc value to the redox potential of the respective HTM. If we set the difference between the TiO 2 Fermi level and the redox potential of HTM at 650 mV, a 5-fold increase in DOS could be found for device C comparing with device D. This explains the larger C m obtained in device C comparing with that in device D.…”

Section: Eis Measurement In the Darkmentioning

confidence: 99%

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The Influence of Charge Transport and Recombination on the Performance of Dye‐Sensitized Solar Cells

et al. 2009

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Electrochemical impedance spectroscopy (EIS) and transient voltage decay measurements are applied to compare the performance of dye sensitized solar cells (DSCs) using organic electrolytes, ionic liquids and organic-hole conductors as hole transport materials (HTM). Nano-crystalline titania films sensitized by the same heteroleptic ruthenium complex NaRu(4-carboxylic acid-4'-carboxylate) (4,4'-dinonyl-2,2'-bipyridyl)(NCS)(2) , coded Z-907Na are employed as working electrodes. The influence of the nature of the HTM on the photovoltaic figures of merit, that is, the open circuit voltage, short circuit photocurrent and fill factor is evaluated. In order to derive the electron lifetime, as well as the electron diffusion coefficient and charge collection efficiency, EIS measurements are performed in the dark and under illumination corresponding to realistic photovoltaic operating conditions of these mesoscopic solar cells. A theoretical model is established to interpret the frequency response off the impedance under open circuit conditions, which is conceptually similar to photovoltage transient decay measurements. Important information on factors that govern the dynamics of electron transport within the nanocrystalline TiO(2) film and charge recombination across the dye sensitized heterojunction is obtained.

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Section: Photovoltage Transient Decay Measurementsmentioning

confidence: 99%

Section: Eis Measurement In the Darkmentioning

confidence: 99%

The Influence of Charge Transport and Recombination on the Performance of Dye‐Sensitized Solar Cells

et al. 2009

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“…The energy offset of the HOMO (-5. 01 eV) relative to that of the spiro-MeOTAD (-4.88 eV) 19 presents enough driving force for the dye regeneration process. Figure 2a shows the certified J-V characteristics of a ssDSC using the C220 dye as the sensitizer, spiro-MeOTAD as the HTM, and a 2.0 μm thick transparent titania film measured at the National Renewable Energy Laboratory (USA) under standard global AM1.5 conditions.…”

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confidence: 97%

An Organic D-π-A Dye for Record Efficiency Solid-State Sensitized Heterojunction Solar Cells

et al. 2011

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D ye-sensitized solar cells (DSCs) have attracted significant attention as low-cost alternatives to conventional semiconductor photovoltaic devices. 1,2 These cells are composed of a nanocrystalline wide band gap semiconductor oxide, e.g., TiO 2 deposited on a transparent conducting oxide (TCO) glass substrate. A molecular sensitizer is linked via an anchoring group to the oxide surface. Upon light excitation, it injects an electron into the conduction band of the semiconductor. Ruthenium complexes as molecular sensitizers have shown impressive solarto-electric power conversion efficiencies (PCE) in liquid electrolyte based devices, with the PCE reaching over 11% under standard AM1.5G full sunlight. [3][4][5][6][7] Recently, metal-free organic dyes have attracted increasing attention due to their high structural flexibility, high molar extinction coefficient, low toxicity, and environmental friendliness. DSCs employing organic dyes featuring an electron donor and acceptor moiety connected by a π-conjugation bridge have reached ∼10% efficiency with liquid electrolytes. [8][9][10][11][12] They can be easily modified to tune their properties for device performance optimization. One of the main factors limiting the performance of DSCs with organic dyes is the formation of dye aggregates on the surface of the semiconductor oxide, leading to quenching of the excited state of the dye molecules and lowering the overall performance of the device. 13 Appropriate molecular structural modifications have been conceived to avoid this undesirable aggregation process. [14][15][16] In solid-state DSCs (ssDSCs) a solid hole-transporting material (HTM) is employed to replace the liquid redox electrolyte which is responsible for the dye regeneration and hole transfer to the counter electrode. Typically, solid HTMs have shorter charge carrier diffusion lengths than liquid redox electrolytes. Due to incomplete pore filling of thicker TiO 2 films with solid HTMs, the ssDSCs are restricted to using thinner titania films. High molar extinction coefficient dyes are of great importance for this type of device in order to enable the use of thinner films. On the basis of this strategy, we have designed and synthesized the 4, 4 0 -didodecyl-4H-cyclopenta[2,1-b:3,4-b 0 ]dithiophene (CPDT) segment which is used as the spacer between the donor and the acceptor group of a metal-free organic sensitizer (called C220).Here, we report on the photovoltaic performance of the C220 sensitizer in a ssDSC using spiro-MeOTAD as the organic holetransporting material.The molecular structure of the C220 dye is presented in Figure 1, which is analogous to the recently reported C218 dye except that dodecyl substituents replace the two hexyl substituents on the CPDT segment. 17 The detailed synthesis of C220 is described in the Supporting Information. The electronic Received: November 18, 2010 Revised: February 7, 2011 ABSTRACT: The high molar absorption coefficient organic D-π-A dye C220 exhibits more than 6% certified electric power conversion efficiency at ...

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“…It is often used to study various redox processes to determine the reversibility of a reaction, the presence of intermediates in redox reactions, electron transfer kinetics, the stability of reaction mediums and many more reaction parameters. In DSSC, CV tends to be used to determine the density of states (DOS) of the nanoporous semiconductor films [38,39] and of the organic hole transport material films [40,41], estimate the energy levels of the dye molecules [2,[42][43][44] and the redox couples [45,46], and evaluate the electrocatalytic activity of the counter electrodes [47][48][49].…”

Section: Cyclic Voltammetrymentioning

confidence: 99%

“…The results correlated well with those obtained using EIS. In addition, García-Cañadas et al [41] used CV to establish energy levels of the hole conductor spiro-OMeTAD and found that its energy levels were changed when it was deposited on indium-doped tin oxide (ITO) to form a film. Their results also showed that the HOMO level of oxidized spiro-OMeTAD was well coupled with the HOMO level of the N719 dye used in the DSSC and that the doping level meant that the material had a high hole concentration allowing it to act as an effective solid electrolyte in the solid-state DSSC.…”

Section: Cyclic Voltammetrymentioning

confidence: 99%

Electrochemical methods for the characterization and interfacial study of dye-sensitized solar cell

Zheng

Wen

et al. 2015

Science Bulletin

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Determination of electron and hole energy levels in mesoporous nanocrystalline TiO2 solid-state dye solar cell

Cited by 66 publications

References 23 publications

The Influence of Charge Transport and Recombination on the Performance of Dye‐Sensitized Solar Cells

The Influence of Charge Transport and Recombination on the Performance of Dye‐Sensitized Solar Cells

An Organic D-π-A Dye for Record Efficiency Solid-State Sensitized Heterojunction Solar Cells

Electrochemical methods for the characterization and interfacial study of dye-sensitized solar cell

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