Parameters Influencing Charge Separation in Solid‐State Dye‐Sensitized Solar Cells Using Novel Hole Conductors

Kroeze, Jessica E.; Hirata, Narukuni; Schmidt‐Mende, Lukas; Orizu, Charles; Ogier, Simon; Carr, K.; Grätzel, Michaël; Durrant, James R.

doi:10.1002/adfm.200500748

Cited by 191 publications

(174 citation statements)

References 40 publications

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“…5,6,7,8,9 Some of these studies have shown that, under optimized conditions and for different dyes and thickness of the TiO2 layer, the dye regeneration yield of the device ranges between 0.9 and 1. This result suggests that either almost complete coverage of the dyed surface is achievable or transfer of holes between the dye molecules enables improved charge collection from dyes that are uncovered by the HTM.…”

Section: Introductionmentioning

confidence: 99%

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Moia¹,

Cappel²,

Leijtens

et al. 2015

J. Phys. Chem. C

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In dye-sensitized solar cells (DSSCs) photo-generated positive charges are normally considered to be carried away from the dyes by a separate phase of hole transporting material (HTM). We show that there can also be significant transport within the dye monolayer itself before the hole reaches the HTM. We quantify the fraction of dye regeneration in solid state DSSCs that can be attributed to this process. By using cyclic voltammetry and transient anisotropy spectroscopy we demonstrate that the rate of inter-dye hole transport is prevented both on micrometer and nanometer length scales by reducing the dye loading on the TiO2 surface. The dye regeneration yield is quantified for films with high and low dye loadings (with and without hole percolation in the dye monolayer) infiltrated with varying levels of HTM. Inter-dye hole transport can account for >50% of the overall dye regeneration with low HTM pore filling. This is reduced to about 5% when the infiltration of the HTM in the pores is optimized in 2μm thick films. Finally, we use hole transport in the dye monolayer to characterize the spatial distribution of the HTM phase in the pores of the dyed mesoporous TiO2.

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Section: Introductionmentioning

confidence: 99%

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

Moia¹,

Cappel²,

Leijtens

et al. 2015

J. Phys. Chem. C

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“…postulated from their study of different HTMs that the PFF may strongly impact the hole injection effi ciency (defi ned as the fraction of photogenerated holes that are successfully injected from dye cations to spiro-OMeTAD). [ 16 ] In a previous study, we estimated that approximately 49% PFF is required to provide a monolayer of dye coverage with spiro-OMeTAD, assuming 20 nm spherical TiO 2 pores and conformal coating of spiro-OMeTAD on adsorbed Z907. [ 13 ] Below this sub-monolayer threshold, a signifi cant fraction of dye molecules are not in contact with spiro-OMeTAD.…”

Section: The Effect Of Hole Transport Materials Pore Filling On Photovmentioning

confidence: 99%

The Effect of Hole Transport Material Pore Filling on Photovoltaic Performance in Solid‐State Dye‐Sensitized Solar Cells

Melas-Kyriazi

Ding

Marchioro

et al. 2011

Advanced Energy Materials

132

104

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A detailed investigation of the effect of hole transport material (HTM) pore filling on the photovoltaic performance of solid‐state dye‐sensitized solar cells (ss‐DSCs) and the specific mechanisms involved is reported. It is demonstrated that the efficiency and photovoltaic characteristics of ss‐DSCs improve with the pore filling fraction (PFF) of the HTM, 2,2’,7,7’‐tetrakis‐(N, N ‐di‐ p ‐methoxyphenylamine)9,9’‐spirobifluorene(spiro‐OMeTAD). The mechanisms through which the improvement of photovoltaic characteristics takes place were studied with transient absorption spectroscopy and transient photovoltage/photocurrent measurements. It is shown that as the spiro‐OMeTAD PFF is increased from 26% to 65%, there is a higher hole injection efficiency from dye cations to spiro‐OMeTAD because more dye molecules are covered with spiro‐OMeTAD, an order‐of‐magnitude slower recombination rate because holes can diffuse further away from the dye/HTM interface, and a 50% higher ambipolar diffusion coefficient due to an improved percolation network. Device simulations predict that if 100% PFF could be achieved for thicker devices, the efficiency of ss‐DSCs using a conventional ruthenium‐dye would increase by 25% beyond its current value.

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“…12 The underperformance of ss-DSC is thought to be associated with three main challenges: (i) limited pore-filling of the mesoporous TiO 2 with the HTM to ensure the optimum composition of the photo-active layer, [13][14][15][16] (ii) panchromatic absorption of light, which is currently limited by the maximal film thickness of well-performing ss-DSCs, 17 and (iii) efficient charge generation and transport from the excited dye to maximize the current output from the sunlight. [18][19][20][21][22][23][24][25] While issues with efficient charge generation have been extensively addressed (though not resolved) in earlier work, [18][19][20][21][22][23][24] the related challenges of effective pore-filling and sufficient panchromatic absorption remains open. The use of novel panchromatic absorbers may extend the absorption range from currently 425-650 nm to 425-940 nm, with a potential gain of 60% extra in short-circuit current and thus a 25% increase in power conversion efficiency despite the accompanied loss in voltage due to the reduced bandgap of the absorber.…”

mentioning

confidence: 99%

Pore Filling of Spiro‐OMeTAD in Solid‐State Dye‐Sensitized Solar Cells Determined Via Optical Reflectometry

Docampo

Hey

Guldin

et al. 2012

Adv Funct Materials

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Here, we present an optical probe to determine the pore-filling fraction of the hole-conductor 2,2-7,7-tetrakis-N,N-di-pmethoxyphenylamine-9,9-spirobifluorene (spiro-OMeTAD) into mesoporous photoanodes in solid-state dye-sensitized solar cells (ss-DSCs). Based on refractive index determination by the film's reflectance spectra, and using effective medium approximations, we can extract the volume fractions of the constituent materials and hence quantify pore-filling. This non-destructive method can be used with complete films and does not require detailed model assumptions.pore-filling fractions of up to 80% were estimated for optimized solid-state DSC photoanodes, which is higher than that previously estimated by indirect methods.Additionally, we have determined transport and recombination lifetimes as a function of the pore-filling fraction via photovoltage and photocurrent decay measurements. While extended electron lifetimes were observed with increasing pore-filling fractions, no trend was found in the transport kinetics. The data suggests that a pore-filling fraction of at least 60% is necessary to achieve optimized performance in ss-DSCs. This degree of pore-filling is even achieved in 5 µm thick mesoporous photoanodes. We can therefore conclude from this study that pore-filling is not a limiting factor in the fabrication of thick ss-DSCs.

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Parameters Influencing Charge Separation in Solid‐State Dye‐Sensitized Solar Cells Using Novel Hole Conductors

Cited by 191 publications

References 40 publications

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

The Role of Hole Transport between Dyes in Solid-State Dye-Sensitized Solar Cells

The Effect of Hole Transport Material Pore Filling on Photovoltaic Performance in Solid‐State Dye‐Sensitized Solar Cells

Pore Filling of Spiro‐OMeTAD in Solid‐State Dye‐Sensitized Solar Cells Determined Via Optical Reflectometry

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