Rational design of Co-based redox mediators for dye-sensitized solar cells by density functional theory

Sun, Zhu-Zhu; Zheng, Kui-Ming; Li, Quan-Song; Li, Ze-Sheng

doi:10.1039/c4ra04605f

Cited by 25 publications

(21 citation statements)

References 64 publications

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“…To yield a high photovoltage, the HOMO of the dye should be favorably low enough. The LUMO levels should lie above the I 3 − /I − or the Co 3+/2+ redox potential (range of −4.8 eV to −5.5 eV) In Table , we present the effective transitions at λ max in the visible region for the different metal ions interacting with the tris‐bipyridine dye and the seven anchoring groups. For most of the cases, the effective transition occurs from a HOMO‐x level to a LUMO+y level.…”

Section: Resultsmentioning

confidence: 99%

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

Sen

Groß

2019

Int J of Quantum Chemistry

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There has recently been a growing interest in dye sensitized solar cells (DSSCs) based on ruthenium metal, but due to the scarcity and high price of ruthenium, design of better and cheaper light adsorbent dyes based on more abundant metal ions is one of the key issues for future development of the DSSCs. Using density functional theory (DFT) and time‐dependent DFT we have studied the properties of new and abundant metal ion‐based polypyridyl dyes for p‐type DSSCs and compared with ruthenium and other scarce metal ions. Molecular geometries, electronic structures, and optical absorption spectra have been calculated using an implicit solvent corresponding to acetonitrile. The calculated fair light harvesting efficiency, high hole injection efficiency and Gibbs free energy for the hole injection and longer excited state lifetime (important for reflecting the efficiency of solar cells) for the new abundant metal ions (V3+ and Cr2+) based dyes could provide promising sensitizers for efficient next generation DSSC's for p‐SC.

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Section: Resultsmentioning

confidence: 99%

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

Sen

Groß

2019

Int J of Quantum Chemistry

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“…36 Moreover, the Cu(I) ion in its spherically symmetric 3d 10 electronic configuration is less sensitive than Co(II) to structural distortions in the ligand coordination sphere. For copper complexes with the smaller reorganization energies, the driving force for dye regeneration can be kept small to obtain improved photovoltages.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…For the three copper complexes, the predicted inner-sphere reorganization energies are very low, about 0.3 eV, in comparison with those of cobalt species: For Co(bpy) 3 and related complexes, the λ in values, computed with the same approach, lie in the range of 0.52−0.63 eV (considering Co(II) low spin) and 1.39−1.78 eV (for Co(II) high spin). 36 We have only addressed the internal (inner-sphere) reorganization energy because recent works from other groups 36,37 have proven that this parameter (λ in ) is the key feature limiting the overall dye regeneration process by Co-based redox mediators.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage

Saygılı¹,

Söderberg²,

Pellet³

et al. 2016

J. Am. Chem. Soc.

252

365

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Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO 2 and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu (II/I) (dmby) 2 TFSI 2/1 (0.97 V vs SHE, dmby = 6,6′-dimethyl-2,2′-bipyridine) and Cu (II/I) (tmby) 2 TFSI 2/1 (0.87 V vs SHE, tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu (II/I) (dmp) 2 TFSI 2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and Cu(II) species, these copper complexes can sufficiently regenerate the oxidized dye molecules with close to unity yield at driving force potentials as low as 0.1 V. The high photovoltages of over 1.0 V were achieved by the series of copper complex based redox mediators without compromising photocurrent densities. Despite the small driving forces for dye regeneration, fast and efficient dye regeneration (2−3 μs) was observed for both complexes. As another advantage, the electron back transfer (recombination) rates were slower with Cu (II/I) (tmby) 2 TFSI 2/1 as evidenced by longer lifetimes. The solar-toelectrical power conversion efficiencies for [Cu(tmby) 2+/1+ based electrolytes were 10.3%, 10.0%, and 10.3%, respectively, using the organic Y123 dye under 1000 W m −2 AM1.5G illumination. The high photovoltaic performance of Cu-based redox mediators underlines the significant potential of the new redox mediators and points to a new research and development direction for DSCs.

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“…According to density functional theory calculations, the predicted inner-sphere reorganization energies (λ in ) were found to be about 0.3 eV, which is very low in comparison with those of Co species. For example, for [Co(bpy) 3 ] 3+/2+ and similar complexes, the λ in values computed with the same approach lie in the range of 0.52-0.63 eV, comparable with the λ in values for Co(II) as low spin; λ in lies in the range of 1.39-1.78 eV for high-spin Co(II)) [150]. With Y123-sensitized devices, U OC values of over 1.0 V was achieved.…”

Section: Copper Mediatorsmentioning

confidence: 54%

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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Rational design of Co-based redox mediators for dye-sensitized solar cells by density functional theory

Abstract: We theoretically describe the effects of chemically modifying polypyridine ligands and design efficient Co-based redox mediators for dye-sensitized solar cells.

Cited by 25 publications

References 64 publications

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

Promising sensitizers for dye sensitized solar cells: A comparison of Ru(II) with other earth's scarce and abundant metal polypyridine complexes

Copper Bipyridyl Redox Mediators for Dye-Sensitized Solar Cells with High Photovoltage

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

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