Kinetic Evidence of Two Pathways for Charge Recombination in NiO-Based Dye-Sensitized Solar Cells

D’Amario, Luca; Antila, Liisa J.; Rimgard, Belinda Pettersson; Boschloo, Gerrit; Hammarström, Leif

doi:10.1021/acs.jpclett.5b00048

Cited by 92 publications

(120 citation statements)

References 23 publications

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“…For cases where β < 0.3, as has been reported for NiO systems,40 the average lifetimes can be quite large, orders of magnitude larger than the time point at which the original data no longer shows a detectable signal. Moreover, the average KWW lifetime is calculated using the ill-behaved Γ function.…”

mentioning

confidence: 74%

“…40 They reported a fast, exponential recombination with τ ≈ 15 ns, followed by a much slower recombination represented by a stretched exponential decay. 40 could be that the present systems do not show recombination on the right time scale for the proposed relaxation effect to be observed: for DPPBr and DPPCN2 almost all recombination occurred already within 1 ns, while in DPP-NDI almost no recombination occurred before 1 µs. The authors therefore proposed that the rapid recombination occurred in parallel to a hole relaxation mechanism that slowed down recombination.…”

Section: Transient Absorption In Solutionmentioning

confidence: 98%

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Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Zhang

Favereau

Farré

et al. 2016

Phys. Chem. Chem. Phys.

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In a photophysical study, two diketopyrrolopyrrole (DPP)-based sensitizers functionalized with 4-thiophenecarboxylic acid as an anchoring group and a bromo (DPPBr) or dicyanovinyl (DPPCN2) group, and a dyad consisting of a DPP unit linked to a naphthalenediimide group (DPP-NDI), were investigated both in solution and grafted on mesoporous NiO films. Femtosecond transient absorption measurements indicate that ultrafast hole injection occurred predominantly on a timescale of ∼200 fs, whereas the subsequent charge recombination occurred on a surprisingly wide range of timescales, from tens of ps to tens of μs; this kinetic heterogeneity is much greater than is typically observed for dye-sensitized TiO2 or ZnO. Also, in contrast to what is typically observed for dye-sensitized TiO2, there was no significant dependence on the excitation power of the recombination kinetics, which can be explained by the hole density being comparatively higher near the valence band of NiO before excitation. The additional acceptor group in DPP-NDI provided a rapid electron shift and stabilized charge separation up to the μs timescale. This enabled efficient (∼95%) regeneration of NDI by a Co(III)(dtb)3 electrolyte (dtb = 4,4'-di-tert-butyl-2,2'-bipyridine), according to transient absorption measurements. The regeneration of DPPBr and DPPCN2 by Co(III)(dtb)3 was instead inefficient, as most recombination for these dyes occurred on the sub-ns timescale. The transient spectroscopy data thus corroborated the trend of the published photovoltaic properties of dye-sensitized solar cells (DSSCs) based on these dyes on mesoporous NiO, and show the potential of a design strategy with a secondary acceptor bound to the dye. The study identifies rapid initial recombination between the dye and NiO as the main obstacle to obtaining high efficiencies in NiO-based DSSCs; these recombination components may be overlooked when studies are conducted using only methods with ns resolution or slower.

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confidence: 74%

Section: Transient Absorption In Solutionmentioning

confidence: 98%

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Zhang

Favereau

Farré

et al. 2016

Phys. Chem. Chem. Phys.

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“…19 The fabrication of the photoelectrode used in this study can be described briefly as follows. A compact NiO layer (60 nm) was sputtered onto a FTO substrate, then a mesoporous NiO layer (1.3 mm) was prepared by doctor-blading NiCl 2 gel on FTO glass and sintered at 450 1C for 0.5 h. 20 In addition, we prepared two reference samples without dye sensitization, denoted NiO-TiO 2 and NiO-Al 2 O 3 -TiO 2 , respectively, to exclude the potential photovoltaic performance from the excitation of the p-n junction formed at the interface of NiO and TiO 2 .…”

Section: -9mentioning

confidence: 99%

Solid state p-type dye sensitized NiO–dye–TiO₂ core–shell solar cells

et al. 2018

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Solid state p-type dye sensitized NiO-dye-TiO 2 core-shell solar cells with an organic dye PB6 were successfully fabricated for the first time.With Al 2 O 3 as an inner barrier layer, the recombination process between injected holes in NiO and injected electrons in TiO 2 was significantly suppressed and the charge transport time was also improved.p-Type dye sensitized solar cells (p-DSCs) have attracted intense interest due to their different charge transfer kinetics with respect to more common studied n-DSCs, 1-3 and the potential application in tandem solar cells 4-6 and solar fuel devices. 7-9The conventional p-DSCs are based on liquid redox electrolytes. To avoid having a liquid phase in the p-DSCs, we have recently proposed and proven the concept of solid state p-DSCs, in which a solid state phenyl-C61-butyric acid methyl ester (PCBM) was used as an electron transport material (ETM) between the dye sensitized photocathode and the back contact. 10 Optimization of photosensitizer represents one strategy to improve the performance of this kind of solar cells. 11,12 Inspired by the conventional dye sensitized TiO 2 solar cells, we proposed that TiO 2 should be an alternative ETM to PCBM due to the fast electron injection from dyes into TiO 2 13,14 and good electron transport property. 15 Thus, we recently fabricated a dye sensitized NiOdye-TiO 2 core-shell film and, in contrast to previous work, [16][17][18] the nanoporous NiO film was first sensitized with the dye and a TiO 2 coating was applied afterwards. This dye sensitized coreshell film showed ultrafast hole (t 1/2 o 120 fs) and electron injection into NiO and TiO 2 respectively, resulting in ultrafast dye regeneration upon electron injection, t 1/2 r 500 fs. 19 In the present work, we proved that the dye sensitized NiO-dye-TiO 2 core-shell mesoporous film can be used for fabrication of solid state p-type dye sensitized solar cells. We also show the effect of an Al 2 O 3 inner barrier layer between NiO and TiO 2 on the performance of solar cell. Fig. 1 shows the configuration and working principle of the proposed p-type dye sensitized NiO-dye-TiO 2 core-shell solar cells. The donor-p-acceptor dye PB6 was utilized as photosensitizer since its reduction/oxidation potentials in excited state match with the valence band of NiO and conduction band of TiO 2 . 19The fabrication of the photoelectrode used in this study can be described briefly as follows. A compact NiO layer (60 nm) was sputtered onto a FTO substrate, then a mesoporous NiO layer (1.3 mm) was prepared by doctor-blading NiCl 2 gel on FTO glass and sintered at 450 1C for 0.5 h.20 Subsequently, the NiO electrode was immersed into 0.2 mM PB6 dichloromethane (DCM) solution overnight. The dye loading in the film was determined to be 31.6 nmol cm À2 by desorption experiment (see ESI †). After rinsing with methanol, the dye sensitized NiO film was dried and coated with metal oxides by atomic layer deposition (ALD). For NiO-PB6-TiO 2 photoelectrode, ca. 10 nm TiO 2 layer was coated directly on a dye sensit...

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“…This aggregation can prevent efficient electron transfer between reduced dye molecules and catalysts. Before the reduction of the catalyst takes place, a recombination event may occur because of electron injection from the reduced dye back into the NiO, which can explain the lack of photocatalytic activity . Another possibility is that the second reduction of the co‐immobilized Ni‐ 1 does not happen, which thus prevents photocatalysis in these cathodes.…”

Section: Resultsmentioning

confidence: 99%

Nickel‐Based Dye‐Sensitized Photocathode: Towards Proton Reduction Using a Molecular Nickel Catalyst and an Organic Dye

et al. 2016

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To construct an efficient dye‐sensitized photo‐electrochemical tandem cell for hydrogen production, it is crucial to understand the working principles of both the photoanode and the photocathode. Herein, the anchoring of a proton‐reduction catalyst and an organic dye molecule on metal oxides is studied for the preparation of a photocathode. On TiO2, the Ni catalyst behaves as a good electrocatalyst (−250 μA cm−2) in acidic water (pH 2). The Ni catalyst and the organic dye were co‐immobilized on NiO to form a solely Ni‐based photocathode. The electron‐transfer steps were investigated by using various techniques (IR, UV/Vis, and fluorescence spectroscopy, and (photo)electrochemistry). Despite the observed successful single‐electron‐transfer steps between all of the components, photocatalysis did not yield any hydrogen gas. Possible bottlenecks that prevent photocatalytic proton reduction are poor electron transfer because of aggregation, charge recombination from the catalyst to the NiO, or instability of the catalyst after the first reduction.

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Kinetic Evidence of Two Pathways for Charge Recombination in NiO-Based Dye-Sensitized Solar Cells

Cited by 92 publications

References 23 publications

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Solid state p-type dye sensitized NiO–dye–TiO₂ core–shell solar cells

Nickel‐Based Dye‐Sensitized Photocathode: Towards Proton Reduction Using a Molecular Nickel Catalyst and an Organic Dye

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Kinetic Evidence of Two Pathways for Charge Recombination in NiO-Based Dye-Sensitized Solar Cells

Cited by 92 publications

References 23 publications

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

Solid state p-type dye sensitized NiO–dye–TiO2 core–shell solar cells

Nickel‐Based Dye‐Sensitized Photocathode: Towards Proton Reduction Using a Molecular Nickel Catalyst and an Organic Dye

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Solid state p-type dye sensitized NiO–dye–TiO₂ core–shell solar cells