Alternative bases to 4-tert-butylpyridine for dye-sensitized solar cells employing copper redox mediator

Ferdowsi, Parnian; Saygılı, Yasemin; Zakeeruddin, Shaik M.; Mokhtari, Javad; Grätzel, Michaël; Hagfeldt, Anders; Kavan, Ladislav

doi:10.1016/j.electacta.2018.01.142

Cited by 40 publications

(52 citation statements)

References 28 publications

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“…The diffusion coefficients were calculated from Equations (2) and 5 The diffusion coefficients for Cu II (tmby) 2 and Cu II (oxabpy) obtained from the cyclic voltammograms are calculated in Table 4. The diffusion coefficient for Cu(tmby) 2 is estimated around 8.6 cm 2 /s, slightly lower but within reasonable agreement with previously reported values from similar experimental setups [41,42]. The higher limiting current for the Cu(oxabpy) system yields a correspondingly 1.7 times higher diffusion coefficient of 14.3 cm 2 /s.…”

Section: Charge Transport In the Cu(oxabpy) Redox Electrolytesupporting

confidence: 89%

“…Diffusion coefficients in the redox electrolytes were deduced from the fitted diffusion resistances R W according to Equation (5). The estimated diffusion coefficient for the diffusion-limiting Cu II (tmby) 2 of 22.4 × 10 −6 cm 2 /s is found in excellent agreement with previously reported values and supports the proposed equivalent circuit model [20,41]. A similar circuit model was applied to fit the impedance spectrum of Cu(oxabpy).…”

Section: Charge Transport In the Cu(oxabpy) Redox Electrolytesupporting

confidence: 81%

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Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells

et al. 2018

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In dye-sensitized solar cells (DSCs), the redox mediator is responsible for the regeneration of the oxidized dye and for the hole transport towards the cathode. Here, we introduce new copper complexes with tetradentate 6,6-bis(4-(S)-isopropyl-2-oxazolinyl)-2,2-bipyridine ligands, Cu(oxabpy), as redox mediators. Copper coordination complexes with a square-planar geometry show low reorganization energies and thus introduce smaller losses in photovoltage. Slow recombination kinetics of excited electrons between the TiO 2 and Cu II (oxabpy) species lead to an exceptionally long electron lifetime, a high Fermi level in the TiO 2 , and a high photovoltage of 920 mV with photocurrents of 10 mA•cm −2 and 6.2% power conversion efficiency. Meanwhile, a large driving force remains for the dye regeneration of the Y123 dye with high efficiencies. The square-planar Cu(oxabpy) complexes yield viscous gel-like solutions. The unique charge transport characteristics are attributed to a superposition of diffusion and electronic conduction. An enhancement in charge transport performance of 70% despite the higher viscosity is observed upon comparison of Cu(oxabpy) to the previously reported Cu(tmby) 2 redox electrolyte.

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Section: Charge Transport In the Cu(oxabpy) Redox Electrolytesupporting

confidence: 89%

Section: Charge Transport In the Cu(oxabpy) Redox Electrolytesupporting

confidence: 81%

Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells

et al. 2018

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“…We also showed that, by using Cu(TFSI) 2 as the starting material, electrochemically clean Cu(II) species can be produced. 31 However, this clean Cu(II) species tends to adopt more complicated coordination spheres in the presence of TBP or other Lewis base additives and exhibits more negative redox potentials. 28,31,32 Following these findings, the DFT computations are carried out for "with TBP" and "without TBP" cases.…”

Section: Acs Applied Energy Materialsmentioning

confidence: 99%

Effect of Coordination Sphere Geometry of Copper Redox Mediators on Regeneration and Recombination Behavior in Dye-Sensitized Solar Cell Applications

Saygılı

Stojanović

Michaels

et al. 2018

ACS Appl. Energy Mater.

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The recombination of injected electrons with oxidized redox species and regeneration behavior of copper redox mediators are investigated for four copper complexes, [Cu(dmby) 2 ] 2+/1+ (dmby = 6,6′-dimethyl-2,2′bipyridine), [Cu(tmby) 2 ] 2+/1+ (tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine), [Cu(eto) 2 ] 2+/1+ (eto = 4-ethoxy-6,6′-dimethyl-2,2′-bipyridine), and [Cu-(dmp) 2 ] 2+/1+ (dmp = bis(2,9-dimethyl-1,10-phenantroline). These complexes were examined in conjunction with the D5, D35, and D45 sensitizers, having various degrees of blocking moieties. The experimental results were further supported by density functional theory calculations, showing that the low reorganization energies, λ, of tetra-coordinated Cu(I) species (λ = 0.31−0.34 eV) allow efficient regeneration of the oxidized dye at driving forces down to approximately 0.1 eV. The regeneration electron transfer reaction is in the Marcus normal regime. However, for Cu(II) species, the presence of 4-tertbutylpyridine (TBP) in electrolyte medium results in penta-coordinated complexes with altered charge recombination kinetics (λ = 1.23−1.40 eV). These higher reorganization energies lead to charge recombination in the Marcus normal regime instead of the Marcus inverted regime that could have been expected from the large driving force for electrons in the conduction band of TiO 2 to react with Cu(II). Nevertheless, the recombination resistance and electron lifetime values were higher for the copper redox species compared to the reference cobalt redox mediator. The DSC devices employing D35 dye with [Cu(dmp) 2 ] 2+/1+ reached a record value for the open circuit voltage of 1.14 V without compromising the short circuit current density value. Even with the D5 dye, which lacks recombination preventing steric units, we reached 7.5% efficiency by employing [Cu(dmp) 2 ] 2+/1+ and [Cu(dmby) 2 ] 2+/1+ at AM 1.5G full sun illumination with open circuit voltage values as high as 1.13 V.

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“…Moreover, electrochemically clean Cu(II)-bipyridine species were produced by electrochemical oxidation of the parent Cu(I) complexes in order to prevent Cl coordination to Cu(II) species. In order to prepare electrochemically clean Cu(II) species, Ferdowsi, et al [153] used Cu(II)(TFSI) 2 as starting species. With this approach, they obtained electrochemically and optically clean Cu(II/I) redox mediator solutions which exhibit improved charge-transfer rate at the CE (PEDOT) and faster diffusion in the solution.…”

Section: Copper Mediatorsmentioning

confidence: 99%

Metal Coordination Complexes as Redox Mediators in Regenerative Dye-Sensitized Solar Cells

et al. 2019

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Dye-sensitized solar cells (DSSCs) have attracted a substantial interest in the last 30 years for the conversion of solar power to electricity. An important component is the redox mediator effecting the transport of charge between the photoelectrode and the dark counter electrode (CE). Among the possible mediators, metal coordination complexes play a prominent role and at present are incorporated in several types of devices with a power conversion efficiency exceeding 10%. The present review, after a brief introduction to the operation of DSSCs, discusses at first the requirements for a successful mediator. Subsequently, the properties of various classes of inorganic coordination complexes functioning as mediators relevant to DSSC operation are presented and the operational characteristics of DSSC devices analyzed. Particular emphasis is paid to the two main classes of efficient redox mediators, the coordination complexes of cobalt and copper; however other less efficient but promising classes of mediators, notably complexes of iron, nickel, manganese and vanadium, are also presented.

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Alternative bases to 4-tert-butylpyridine for dye-sensitized solar cells employing copper redox mediator

Cited by 40 publications

References 28 publications

Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells

Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells

Effect of Coordination Sphere Geometry of Copper Redox Mediators on Regeneration and Recombination Behavior in Dye-Sensitized Solar Cell Applications

Metal Coordination Complexes as Redox Mediators in Regenerative Dye-Sensitized Solar Cells

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