Molecular design of metal-free D–π-A substituted sensitizers for dye-sensitized solar cells

Alibabaei, Leila; Kim, J.-H.; Wang, Mingkui; Pootrakulchote, Nuttapol; Teuscher, Joël; Censo, Davide Di; Humphry‐Baker, Robin; Moser, Jacques-E.; Yu, Yi; Kay, Kwang‐Yol; Zakeeruddin, Shaik M.; Grätzel, Michaël

doi:10.1039/c0ee00218f

Cited by 73 publications

(35 citation statements)

References 26 publications

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“…The synthesis of SD-1, SD-2, and SD-5 was reported elsewhere. 9 The dyes SD-3 and SD-4 were synthesized according to the steps depicted in Scheme 1. Every step of the reaction sequence proceeded smoothly and efficiently to give a good or moderate yield of the product.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…9 It has been proposed that in addition to the red shift of the spectral response caused by inserting the thiophene units, their insertion favors the creation of charge recombination centers. Nanosecond flash photolysis studies of SD-1, SD-2, and SD-5, supported this contention, showing significant differences of the charge recombination rate constants with the insertion of thiophenes between the donor and acceptor.…”

Section: ■ Introductionmentioning

confidence: 99%

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Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Wielopolski

Kim²,

Jung³

et al. 2013

J. Phys. Chem. C

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A series of five organic donor-π-bridge-acceptor (D-π-A) sensitizers is investigated within the context of their photoinduced charge-transfer properties. Thereby, the focus is set on the impact of structural modifications of the molecular architecture on the π-systems of the dyes. In particular, two different modes of systematic extension of the sensitizers' π-systems, namely, (i) within the electron donating site and (ii) within the π-bridge, are investigated by means of steady-state and time-resolved spectroscopic methods. The photophysical studies of the molecules in solution and as deposited on Al 2 O 3 or TiO 2 films reveal that different effects on the charge-transfer characteristics evolve dependent where − within the molecular structure − the modification of the π-system is performed. Hence, π-extension of the donor sites, for instance, leads to a strong red shift of the absorption features and a variation of light-harvesting properties. Modifying the π-bridges results in a spatial decoupling of the HOMO and LUMO orbitals, which goes along with changes of the electronic coupling to TiO 2 . Furthermore, solution studies show that the electronic structure of the dyes governs their singlet excited-state features. As shown, the results obtained from these studies then allow important predictions about the deactivation of the excited states of these molecules adsorbed on TiO 2 . Finally, quantum chemical methods − among others, time-dependent density functional theory calculations − provide conclusive insight into the relationship between the electronic structure of the dyes and its impact on the photoinduced charge-transfer characteristics. ■ INTRODUCTIONThe advantages of metal-free organic sensitizers, for the application in dye-sensitized solar cells (DSSCs), place them more and more into the focus of sensitizer research and development. Superior to their ruthenium-containing alternatives 1 are their extinction coefficients and the nearly unlimited possibilities of varying parameters such as the overall π-conjugation, the distance between the donor and the acceptor, and the nature of the anchoring groups by wellestablished synthetic methods.2 This allows for fine-tuning the spectral and electronic features as well as for a control over charge-transfer kinetics and electronic coupling to TiO 2 . Understanding the influence of structural variations to the sensitizer, such as the length of π-conjugation or anchoring/ acceptor group choice on the DSSC device performance, is crucial for advancing this field and technology. 3,4 Critical factors that influenced performance properties are (i) the excited-state redox potentials, which should be properly aligned with the conduction band of TiO 2 , (ii) the light-harvesting features of the sensitizer, (iii) the conjugation across the donor and anchoring groups, and (iv) the electronic coupling between the lowest unoccupied molecular orbital (LUMO) and the conduction band of the TiO 2 .5 It has been shown that a sensitive interplay between all of these fact...

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Wielopolski

Kim²,

Jung³

et al. 2013

J. Phys. Chem. C

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“…Recently, novel organic dyes based on coumarin [9][10][11], merocyanine [12,13], indoline [14][15][16], polyene [17], hemicyanine [18,19], fluorene [20][21][22], anthracene [23], triphenylamine [24][25][26][27][28][29], ethylenedioxythiophene [30], diketopyrrolepyrrole (DPP) [31], phenothiazine [32] and tetrahydroquinoline [33] have been developed and showed good performance.…”

Section: Introductionmentioning

confidence: 99%

Effect of chenodeoxycholic acid (CDCA) additive on phenothiazine dyes sensitized photovoltaic performance

Yang

et al. 2011

Sci. China Chem.

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The effects of chenodeoxycholic acid (CDCA) in a dye solution as a co-adsorbent on the photovoltaic performance of dye-sensitized solar cells (DSSCs) based on two organic dyes containing phenothiazine and triarylamine segments (P1 and P2) were investigated. It was found that the coadsorption of CDCA can hinder the formation of dye aggregates and improve electron injection yield and thus J sc . This has also led to a rise in photovoltage, which is attributed to the decrease of charge recombination. The DSSC based on dye P2 showed better photovoltaic performance than P1: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 89.5%, a short-circuit photocurrent density (J sc ) of 9.57 mA/cm 2 , an open-circuit photovoltage (V oc ) of 697 mV, and a fill factor (FF) of 0.66, corresponding to an overall conversion efficiency of 4.42% under the standard global AM 1.5 solar light condition. The overall conversion efficiency was further improved to 5.31% (J sc = 10.36 mA/cm 2 , V oc = 0.730 V, FF = 0.70) upon addition of 10 mM CDCA to the dye solution for TiO 2 sensitization. Electrochemical impedance data indicate that the electron lifetime was improved by coadsorption of CDCA, accounting for the significant improvement of V oc . These results suggest that interfacial engineering of the organic dye-sensitized TiO 2 electrodes is important for highly efficient photovoltaic performance of the solar cell. dye-sensitized solar cells, phenothiazine, additive, co-adsorption

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“…The sintered TiO 2 electrodes were immersed for established time in the respective dye solutions, dried by blowing nitrogen, and then assembled with a thermal platinized FTO/glass counter electrode. The working and counter electrodes, separated by a 25 mm thick hot melt ring (Surlyn, DuPont), were sealed by heating; in the internal space Z960 electrolyte [27] was added with a vacuum pump and a Surlyn sheet covered with a thin glass has been used for sealing the hole. Schott K113 Tempax sunlight filter (Präzisions Glas & Optik GmbH, Germany) was used to match the spectral output of the lamp in the region of 350-750 nm so as to reduce the mismatch between the simulated and true solar spectra to less than 2%.…”

Section: Device Fabricationmentioning

confidence: 99%

Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO₂Thin Films with Porphyrin Dyes for DSSC Applications

Giovannetti

Zannotti

Alibabaei

et al. 2014

International Journal of Photoenergy

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Free base, Cu(II) and Zn(II) complexes of the 2,7,12,17-tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (CPI) in solution and bounded to transparent monolayer TiO2nanoparticle films were studied to determine their adsorption on TiO2surface, to measure the adsorption kinetics and isotherms, and to use the results obtained to optimize the preparation of DSSC photovoltaic cells. Adsorption studies were carried out on monolayer transparent TiO2films of a known thickness. Langmuir and Frendlich adsorption constants of CPI-dyes on TiO2monolayer surface have been calculated as a function of the equilibrium concentrations in the solutions. The amount of these adsorbed dyes showed the accordance with Langmuir isotherm. Kinetic data on the adsorption of dyes showed significantly better fits to pseudo-first-order model and the evaluated rate constants linearly increased with the grow of initial dye concentrations. The stoichiometry of the adsorption of CPI-dyes into TiO2and the influence of presence of coadsorbent (chenodeoxycholic acid) have been established. The DSSC obtained in the similar conditions showed that the best efficiency can be obtained in the absence of coadsorbent with short and established immersion times.

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Molecular design of metal-free D–π-A substituted sensitizers for dye-sensitized solar cells

Cited by 73 publications

References 26 publications

Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Effect of chenodeoxycholic acid (CDCA) additive on phenothiazine dyes sensitized photovoltaic performance

Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO₂Thin Films with Porphyrin Dyes for DSSC Applications

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Molecular design of metal-free D–π-A substituted sensitizers for dye-sensitized solar cells

Cited by 73 publications

References 26 publications

Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Position-Dependent Extension of π-Conjugation in D-π-A Dye Sensitizers and the Impact on the Charge-Transfer Properties

Effect of chenodeoxycholic acid (CDCA) additive on phenothiazine dyes sensitized photovoltaic performance

Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO2Thin Films with Porphyrin Dyes for DSSC Applications

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Product

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Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO₂Thin Films with Porphyrin Dyes for DSSC Applications