Dyes For DSSC Research Articles

A DFT/TD-DFT Study of the Influence of Anchoring Group and Internal Acceptor of Benzocarbazole-based D-A´-π-A Dyes for DSSCs

Great attention is being shifted to Dye-sensitized solar cells because of their structural and electronic tunability, high performance, and low cost compared to conservative photovoltaic devices. In this work, the DFT/B3LYP/6-31G(d,p) and TD-DFT/mPW9PW91/6-31G(d,p) levels of theory are applied to the theoretical study of a new class of benzocarbazole-based D-A´-π-A dyes for their potential use in DSSCs. The influence of the internal acceptor on the optoelectronic properties is studied for the dyes. The optoelectronic and photovoltaic properties as HOMO, LUMO, E<sub>gap</sub> maximum absorption wavelength (λ<sub>max</sub>), vertical excitation energies (E<sub>ex</sub>), oscillator strength (<i>f</i>), light harvesting efficiency (LHE), open circuit voltage (V<sub>oc</sub>), injection force (ΔG<sub>inject)</sub>, were evaluated and discussed in order to compare their performance as DSSC sensitizers. The theoretical results show that all dyes exhibit excellent optoelectronic properties, such as a lower E<sub>gap</sub>(1.733 eV to 2.173 eV), a significant λ<sub>max</sub>(631.48 nm to 754.40 nm), a sufficient value of V<sub>oc</sub> (0.461 V to 0.880 V) and high LHE (0.853 eV to 0.968 eV). In particular M4 with 2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dithione as auxiliary acceptor has the potential to be used as a sensitizer for DSSCs, due to its red-shifted absorption spectrum (λ<sub>max</sub>= 754.40 nm), and small energy gap (E<sub>gap</sub>=1.733 eV). Indeed, this study may help chemists to synthesize efficient dyes for DSSC.

Retraction: Novel ethynyl-pyrene substituted phenothiazine based metal free organic dyes in DSSC with 12% conversion efficiency

Retraction of ‘Novel ethynyl-pyrene substituted phenothiazine based metal free organic dyes in DSSC with 12% conversion efficiency’ by Bhanumathi Nagarajan et al., J. Mater. Chem. A, 2017, 5, 10289–10300, https://doi.org/10.1039/C7TA01744H.

New A3B-type naphthyl Zn(II) porphyrins as DSSC dyes: Effect of anchoring group and co-adsorption for enhanced efficiency

Two new Zn(II) porphyrin dyes ZnNPCA and ZnNPHy bearing three naphthyl groups and one carboxyphenyl/hydroxyphenyl anchoring group in an A3B meso substitution pattern was synthesized utilizing a mixed condensation approach. The redshifted absorption bands to 427 nm as impacts on the extended conjugation with three naphthyl substituents. Similarly, the emission spectrum also exhibits a redshift than ZnTPP-COOH dye. The anodic shift was found in the reduction potential of the naphthyl dyes with the carboxylic acid anchor (ZnNPCA), facilitating the more favourable electron injection. Moreover, the naphthyl porphyrin dyes positively interacted with semiconducting TiO2, whose binding mode was further established using FT-IR. While interacting with titania, the more broadening absorption spectra exhibit strong electronic coupling and will benefit the electron injection. The high dye loading amount obtained for ZnNPCA dye was 13.1 × 10−8 mol cm2, which is more significant towards light harvesting. DSSC devices were fabricated using porphyrin-sensitized photoanodes. ZnNPCA showed better efficiency than ZnNPHy owing to higher dye loading onto the titania surface. Furthermore, the influence of co-adsorbent DCA on the photovoltaic performance of the fabricated DSSC devices was investigated. As a result, a maximum efficiency of 1.85% was achieved for ZnNPCA/DCA device. In addition, electrochemical impedance spectroscopy results revealed a higher electron lifetime (6.14 ms) for this device, supporting better suppression of back reactions.

New naphthalenediimides as potential dyes for TiO2-sensitized solar cells

In this work new naphthalenediimides (NDIs) were synthesized and used as dyes in DSSC. The efficiency (η) of the DSSC is influenced by NDIs electronic and structural characteristics. It was found a better cell performance with the NDIs which have a broader absorption band shifted to the red color, high ƹ values, and more adsorption in the anode surface. The band gaps were determinate by UV–vis and cyclic voltammetry. The LUMO orbitals of most of the NDIs are above of the conduction band (CB) energy for TiO2 allowing the electron transfer process from the NDI to the photoanode, especially in those with a significant LUMONDI-CBTi energetic difference. Also, NDIs with polar groups in their structure presented higher η values due to a better adsorption on the photoanode surface, which allows a better energy capture compared with those with lower adsorption.

Phenothiazine and phenoxazine sensitizers for dye-sensitized solar cells – an investigative review of two complete dye classes

A compete statistical review of phenothiazine DSSC dyes, identifying the traits of successful phenothiazine dyes and uncovering inherent molecular limitations.

Position engineering of cyanoacrylic-acid anchoring group in a dye for DSSC applications

This study provides insights into the molecular tailoring of DSSC dyes via synthesis/investigation of three new organic dyes with the position engineering of the acceptor moiety. Differences in photophysical, electrochemical and photovoltaic properties are found and interpreted in detail. The excitation-spectrum study shows that the population of the intramolecular charge transfer (ICT) is incident-wavelength dependent; and the ICT excitons originate not only from direct ICT band transition but also from π-π* energy transfer, and the degree of the latter depends much on the position of the anchoring group. The transient photoluminescence discloses that the non-injection quenching of the ortho dye is the most severe possibly due to the instability of the excited state resulting from the hurdling of electron delocalization by the large steric hinderance. Large steric hinderance in the ortho dye also results in the least dye loading on TiO2 photoanode. Due to broader/stronger absorption, higher dye loading, high injection efficiency and low charge recombination rate, the para-substituted dye DSSC device achieves the best performance with power conversion efficiency of 6.63%; while the ortho dye based device performs the worst with significant lower of photocurrent and photovoltage compared to the para dye. The dye dependent VOC is explained by combination of dipole moment and dye loading. Particularly, the employing of excitation spectrum as tools to investigate the intrinsic photophysical complicity of dyes with D-π-A structure, which is scarcely reported, is proved to be an effective way.

Consecutive Three-Component Synthesis of Donor-Substituted Merocyanines by a One-Pot Suzuki–Knoevenagel Condensation Sequence

The consecutive three-component Suzuki-Knoevenagel condensation (SuKnoCon) synthesis is an efficient, modular one-pot synthetic approach to donor-substituted merocyanines with carboxylic acid functionality. A library of 19 dyes is readily accessible and their electronic properties can be assessed by cyclic voltammetry and absorption and emission spectroscopy. In addition, for illustration of the utility of this concise one-pot concept, several dyes from this library were identified to be well suited as DSSC dyes with relative efficiencies reaching up to 93% of Grätzel's dye N3.

Comparison of Conductivity Performance of Dragon Fruit Dye Extracted Using Water and Ethanol for Dye Sensitized Solar Cells

Natural pigments such as anthocyanin, carotenoid, flavonoids, and chlorophyll can be considered as promising alternative sensitizer dyes for DSSC to replace synthetic dye such as N719 because of their simple preparation technique, low cost, complete biodegradation, availability, purity grade, environmental friendliness and most importantly ability to reduce noble metal. In this work, UV-Vis spectra is used to observe the absorption spectra of different extracting solvent of dragon fruit dye. Fourier Transform Infrared Spectroscopy (FTIR) identifies the functional components of the dye while impedance spectroscopy gives the conductivity data. Dragon fruit dye extracted with ethanol had a lower absorbance at 518 nm compared to dragon fruit dye extracted with distilled water at 521 nm. The presence of carboxyl group in Betalains pigment within the range of 400 - 700 nm wavenumber promotes strong hydrogen bonding while the presence of COOH stretching vibration further confirms the carboxyl group of Betalains derivatives in dragon fruit dye. The electrical conductivity measured at room temperature (27°C), boiling point (100°C) and 130°C recorded highest value of 183 Scm-1 at 100 °C for dragon fruit dye diluted with distilled water (D-DI) while for dragon fruit dye diluted with ethanol (D-Etha) the value is 9.56 × 10-1 Scm-1 at 130°C hence showing that distilled water is the best solvent for natural dye from dragon fruit.

Photoexcited Phenyl Ring Twisting in Quinodimethane Dyes Enhances Photovoltaic Performance in Dye-Sensitized Solar Cells

Four metal-free organic quinodimethane-based dyes, which represent molecular building blocks for a new class of DSSC dyes, were studied with the objective to improve their photovoltaic performance via molecular engineering strategies. Such strategies can only be systematic and successful if they are derived from knowledge-based paradigms that relate individual aspects of the molecular structure for a given class of dyes to their photovoltaic properties. The optical and electrochemical properties of these dyes were investigated experimentally by UV–vis absorption and emission spectroscopy, as well as cyclic voltammetry and electrochemical impedance spectroscopy. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations on these dyes complement these experiments. Among other results, this concerted experimental and computational study revealed that the dialkylaminophenyl moiety in these dyes exhibits a large twist as a result of its ground-to-excited-state optical transition. In particula...

Orbital and molecular design of new naphthyl-salen type transition metal complexes toward DSSC dyes

Orbital and molecular design of new naphthyl-salen type transition metal complexes toward DSSC dyes

Effect of solvents in the extraction and stability of anthocyanin from the petals of Caesalpinia pulcherrima for natural dye sensitized solar cell applications

Anthocyanin, a flavonoid pigment is responsible for wide range of coloration in petals of flowers and fruits, absorbs broad range of visible light. This makes them suitable to be used as dyes for DSSC. But, the efficiency of natural dyes is not up to the mark mainly due to anthocyanin instability. The stability issues in vitro are mainly due to the effect of solvents on extraction of anthocyanins and their respective pH. Taking this factor into consideration, in the present work, the anthocyanins were extracted from the flower Caesalpinia pulcherrima (C. pulcherrima) with various solvents and their respective stability and pH values are discussed. The usage of citric acid as solvent to extract anthocyanin has shown good stability than other solvents. It also helps in enhancing the sensitization properties of anthocyanins with titanium dioxide (TiO2) nanorods. The IPCE spectra show higher photovoltaic performance for dye sensitized TiO2 nanorods using citric acid as solvent. The natural DSSC using citric acid as solvent shows a higher efficiency of 0.83% compared to other solvents. Hence citric acid performs to be a safe solvent for natural DSSC in boosting the photovoltaic performance and maintaining the stability of anthocyanins.

New dyes for DSSC containing triphenylamine based extended donor: Synthesis, photophysical properties and device performance

Three new triphenylamine based dyes with Donor-Donor-Spacer-Acceptor (D-D-π-A) arrangement were designed and synthesized by convenient synthetic pathway. Unsymmetrical extended donor part may help to reduce the aggregation of dyes on the semiconductor surface. Wide range of absorption in the visible spectrum, electrochemical studies and theoretical optimization suggest that these dyes can be good members for DSSC. Further to check the performance of these dyes in device the solar cells were developed using iodine free Co-based electrolyte. Electronic characterisation concludes that devices based on D6 have the highest power conversion efficiency (4.7%) mostly due to an improved electron lifetime, which therefore improves both the VOC and JSC of the devices.

Novel ethynyl-pyrene substituted phenothiazine based metal free organic dyes in DSSC with 12% conversion efficiency

Six new dyes based on phenothiazine conjugated to an ethynyl-pyrene moiety are synthesized and characterized.

Trans -disubstituted benzodiazaporphyrin: A promising hybrid dye between porphyrin and phthalocyanine for application in dye-sensitized solar cells

We have synthesized a zinc benzodiazaporphyrin trans-substituted by a di-(3,5-tert-butyl)phenyl and 4-phenyl carboxylic acid groups (coded CROSSDAP). This new dye has been characterized by UV–vis absorption and emission spectroscopy, electrochemical measurements and modeled using TD-DFT calculations. CROSSDAP exhibits interesting absorption properties which resemble those of a zinc phthalocyanine; that is an intense Q-band localized at 685 nm. CROSSDAP was used as sensitizer on nanocrystalline TiO2 based Dye-Sensitized Solar Cells with iodide/triiodide electrolyte. The solar cell reaches a 3.37% power conversion efficiency under AM1.5 with an IPCE value over 40% at 680 nm. CROSSDAP can axially bind an imidazole ligand substituted with a Bodipy dye. When used as additive in the electrolyte, the latter antenna amplifies the light harvesting efficiency of CROSSDAP in the 450–550 nm range, a feature which increases the photocurrent up to 8.40 mA/cm2 resulting in a PCE of 3.82%. Overall, these results demonstrate that trans-substituted benzodiazaporphyrins are attractive new dyes for DSSC, particularly towards the development of efficient sensitizers to harvest the low energy part of the visible spectrum.

Benzodithiophene based organic dyes for DSSC: Effect of alkyl chain substitution on dye efficiency

A series of push–pull triarylamine organic dyes containing the benzo[1,2-b:4,5-b′]dithiophene unit as a spacer and bearing alkyl chains in different positions of the molecule were synthesized. The new dyes 1–4 were characterized by optical and electrochemical measurements and density functional theory calculations and used as sensitizers in liquid dye-sensitized solar cells. The effect of alkyl chain position on dye properties and performances was investigated and dye 1, bearing two 3,7-dimethyloctyl groups on the benzodithiophene core, exhibited the best behaviour in term of light absorption and cell performance (PCE of 6.6%, to be compared with a PCE of 8.1% for N719-based device). The efficiency of the DSSC was highly dependent on the solvent used for the dye-sensitizing bath, which affects the position of the COOH/COO− equilibrium.

Relationship between measurement conditions and energy levels in the organic dyes used in dye-sensitized solar cells

The energy levels of new metal-free organic dyes for DSSC have been investigated by the photoemission in air, UV-Vis absorption and CV methods in the solutions of the dye molecules, in films of the dyes and in the dyes adsorbed on nanoporous TiO2.

Planar amine-based dye features the rigidified O-bridged dithiophene π-spacer: A potential high-efficiency sensitizer for dye-sensitized solar cells application

This work reports a systematically theoretical study concerning the design of D–π–A organic dyes for DSSC. Two elaborate strategies, namely the rigidity of dithiophene and introduction of strong electron rich/deficient moieties, are proposed. By using the state-of-the-art theoretical calculations, the general influences of fastening atoms (C, N, and O) for π-spacer rigidification in planar amine-based organic dyes are firstly investigated and elucidated. The properties of isolated dye, dye/(TiO2)38, and dye–I2 interaction are discussed in detail. The results show that, compared with the P2T dye containing dithiophene π-spacer, its three counterparts with rigidified dithiophene π-spacers would present the improved absorption properties. We further demonstrate that incorporation of O-bridged dithiophene moiety into the π-spacer was promising to challenge the photoelectric conversion efficiency 8.29% of P2T. Furthermore, benzothiadiazole (BTD) and 3,4-ethylenedioxythiophene (EDOT) moieties are the well-known π-skeletons that can effectively tune the electronic structure properties and the light-harvesting ability. Subsequently, a series of dyes are designed through introducing the BTD and EDOT groups into π-spacer. The calculated results reveal that the dye with the incorporation of EDOT moiety would be more beneficial for photocurrent and photovoltage performance. The current theoretical studies are expected to be very relevant for the molecular design of D–π–A organic dyes in DSSC.

Effect of COOH group on the performance of rhenium (I) tricarbonyl complexes with tetrathiafulvalene-fused phenanthroline ligands as dyes in DSSC: DFT/TD-DFT theoretical investigations

A series of rhenium (I) tricarbonyl complexes Re(CO)3Cl(HnL) (n = 1, a1–a3; n = 2, b1–b9; L = 4′, 5′-bis(carboxyl)dithiotetrathiafulvenyl[4,5-f] [O’regan,Nature,353:737-740, O’regan and Gratzel 1991;Drgnonetti C,Inorg Chim Acta,388:163-167, Dragnonetti et al. 2012] phenanthroline; a and b indicate the number for COOH group; 1–9 indicates different positions for COOH group on phenanthroline) have been investigated theoretically to explore the effect of COOH functional group on their electronic structures, spectroscopic properties, and their properties as dye in a solar cell. The different numbers and positions of carboxyl group on phenanthroline (Phen) ligand in designed complexes significantly changed the HOMO–LUMO energy gap smaller than the parent complex Re(CO)3Cl(L) (2). Therefore, the absorptions of most designed complexes have an obvious red shift compared with 2. Furthermore, the values of driving force (D) and light-harvesting efficiency (LHE) have been calculated and compared. According to the results above, we find 2-position COOH (a2) and 2,3-position COOH (b9) own both good optical properties and enough driving force, and predict that a2 in a1–a3 and b9 in b1–b9 may have better performance as the dye sensitizer than other designed dyes.

Excited State Geometries and Vertical Emission Energies of Solvated Dyes for DSSC: A PCM/TD-DFT Benchmark Study.

The ability of Time-Dependent Density Functional Theory (TD-DFT) to provide excited state geometries and reproduce emission energies of organic D-π-A dyes designed for DSSC applications is evaluated. The performance of six functionals (CAM-B3LYP, MPW1K, ωB97X-D, LC-BLYP, LC-ωPBE, and M06-HF) in combination with three basis sets (cc-pVDZ, 6-31+G(d,p), and 6-311+G(2d,p)) has been analyzed. Solvent effects have been taken into account by means of a Polarizable Continuum Model in both LR and SS formalisms. Our LR-PCM/TD-DFT results show that accurate emission energies are obtained only when solvent effects are included in the computation of excited state geometries and when a range separated hybrid functional is used. Vertical emission energies are reproduced with a mean absolute error of at most 0.2 eV. The accuracy is further improved using the SS-PCM formalism.

ChemInform Abstract: β‐(Ethynylbenzoic acid)‐substituted Push—Pull Porphyrins: DSSC Dyes Prepared by a Direct Palladium‐Catalyzed Alkynylation Reaction.

The palladium-catalyzed oxidative alkynylation of β-borylated porphyrins allows for concise preparation of push–pull structured ethynylbenzoic acid porphyrin derivatives. The resulting β-singly- and doubly-substituted porphyrin dyes are regarded as isomeric derivatives of the corresponding meso-substituted reference systems, and were found to give rise to nearly equal power conversion efficiencies when analyzed in DSSCs.