Meso-substituted porphyrins for dye-sensitized solar cells

Phosphonate-Derivatized Porphyrins for Photoelectrochemical Applications

A series of phosphonate-derivatized, high redox potential porphyrins with mesityl, pentafluorophenyl, and heptafluoropropyl meso-substituents were synthesized by acid-catalyzed condensation reactions. Ground and excited state redox potentials in the series were varied systematically with the electron-donating or electron-accepting nature of the meso-substitutents. The extent of excitation and injection by porphyrin singlet excited states surface-bound to SnO2/TiO2 core/shell metal oxide nanoparticle films varies with the excited state reduction potential, E°(')(P(+)/P*). With the mesityl-substituted porphyrin, high current density and sustained photocurrents are observed at pH 7 with the addition of the electron transfer donor hydroquinone.

Influence of Phenylethynylene of Push-Pull Zinc Porphyrins on the Photovoltaic Performance

A series of zinc porphyrin dyes YD22-YD28 were synthesized and used for dye-sensitized solar cells. Dyes YD26-YD28 consist of zinc porphyrin (ZnP) as core unit, arylamine (Am) as electron-donating group, and p-ethynylbenzoic acid (EBA) as an electron-withdrawing/-anchoring group. The dyes YD22-YD25 contain additional phenylethynylene group (PE) bridged between Am and ZnP units. The influence of the PE unit on molecular properties as well as photovoltaic performances were investigated via photophysical and electrochemical studies and density functional calculations. With the insertion of PE unit, the dyes YD22-YD25 possess better light-harvesting properties in terms of significantly red-shifted Q-band absorption. The conversion efficiencies for dyes YD22-YD25 are better than those of dyes YD26-YD28 owing to larger J(SC) output. Natural transition orbitals and Mulliken charge analysis were used to analyze the electron injection efficiency for porphyrin dyes upon time-dependent DFT calculations. The results indicated that insertion of additional PE unit is beneficial to higher J(SC) by means of improved light-harvesting property due to broadened and red-shifted absorption.

Improvement of photovoltaic performance by substituent effect of donor and acceptor structure of TPA-based dye-sensitized solar cells

We report a computational study of a series of organic dyes built with triphenylamine (TPA) as an electron donor group. We designed a set of six dyes called (TPA-n, where n = 0-5). In order to enhance the electron-injection process, the electron-donor effect of some specific substituent was studied. Thus, we gave insights into the rational design of organic TPA-based chromophores for use in dye-sensitized solar cells (DSSCs). In addition, we report the HOMO, LUMO, the calculated excited state oxidized potential E(dye*)(eV) and the free energy change for electron-injection ΔGinject(eV), and the UV-visible absorption bands for TPA-n dyes by a time-dependent density functional theory (TDDFT) procedure at the B3LYP and CAM-B3LYP levels with solvent effect. The results demonstrate that the introduction of the electron-acceptor groups produces an intramolecular charge transfer showing a shift of the absorption wavelengths of TPA-n under studies. Graphical Abstract Several organic dyes TPA-n with different donors and acceptors are modeled. A strong conjugation acrros the donor and anchoring groips (TPA-n) bas been studied. Candidate TPA-3 shows a promising results.

Synthesis and characterization of simple cost-effective trans-A2BC porphyrins with various donor groups for dye-sensitized solar cells

Zn(ii) porphyrin dyes have been synthesized in three steps and exhibited power conversion efficiencies of 2.1 to 4.2% which depend on the electron donating ability of the R group.

Shifting UV-vis absorption spectrum through rational structural modifications of zinc porphyrin photoactive compounds

Metalloporphyrin assemblies such as Zn–porphyrins are significant photoactive compounds with a number of applications including molecular devices and dye-sensitized solar cells (DSSC).

Synthesis of porphyrin sensitizers with a thiazole group as an efficient π-spacer: potential application in dye-sensitized solar cells

CNU-OC8 exhibits better photovoltaic performance than the benchmark YD2-OC8 sensitizer in a liquid I⁻/I₃⁻ redox electrolyte.

Progress on nanoparticle-based carbon nanotube complex: fabrication and potential application

Carbon nanotubes (CNTs) are considered as one of the most intensively explored nanostructured materials and have been widely used as a platform material for metal and semiconductor nanoparticles (NPs) due to their large and chemically active surface area. Several approaches have been described in the literature to immobilize NPs on the surface of CNTs. This report reviews the recent developments in this area by exploring the various techniques where nanotubes can be functionalized with NPs to improve the optical, mechanical, thermal, medical, electrical, and magnetic applications of CNTs.

Engineering the optoelectronic properties of MoS2 photodetectors through reversible noncovalent functionalization

The photoresponse of MoS₂ photodetectors is enhanced through simple and reversible functionalization with organic dyes.

Recent advances in the template-directed synthesis of porphyrin nanorings

This Feature Article reviews recent advances in the template-directed synthesis of porphyrin nanorings, including new templating methods, novel structures, and their applications in host–guest chemistry and artificial light-harvesting.

A low recombination rate indolizine sensitizer for dye-sensitized solar cells

A novel indolizine donor for DSC use with an extended absorption spectrum shows good voltages and enhanced short circuit current.

Insight into the effects of modifying π-bridges on the performance of dye-sensitized solar cells containing triphenylamine dyes

The photovoltaic performances of four novel dyes (ZHG1, ZHG2, ZHG3 and ZHG4) indicate that it is very important to find a balance point between the electron injection ability, intermolecular π–π aggregation and the expansion of the light absorption range.

Synthesis and conformation of a novel fluorescein–Zn-porphyrin dyad and intramolecular energy transfer

Modulations of the optical properties of a new porphyrin–fluorescein dyad were elucidated using experimental and theoretical techniques, with conformational rearrangements being studied.

Pyridyl vs. bipyridyl anchoring groups of porphyrin sensitizers for dye sensitized solar cells

Two D–π–A porphyrins (A = pyridyl, bipyridyl) are synthesized and used as sensitizers in DSSCs. The enhanced photovoltaic performance of the bipyridyl-sensitized device is attributed to its faster electron injection and reduced charge recombination.

Phenothiazine-functionalized push–pull Zn porphyrin photosensitizers for efficient dye-sensitized solar cells

A series of zinc porphyrin dyes (JY24–27) featured phenothiazine moieties have been synthesized and applied as photosensitizers in dye-sensitized solar cells.

Two new bulky substituted Zn porphyrins bearing carboxylate anchoring groups as promising dyes for DSSCs

Two novel zinc-metallated porphyrins, bearing three and six long alkoxy chains at the periphery, have been synthesized as sensitizers in DSSCs.

New D–D–π–A type organic dyes having carbazol-N-yl phenothiazine moiety as a donor (D–D) unit for efficient dye-sensitized solar cells: experimental and theoretical studies

DSSCs using novel organic dyes (CPhTnPA, n = 0–2) with carbazol-N-yl phenothiazine moiety as a donor (D–D) unit as the sensitizers exhibited efficiency as high as 7.78% which reached 95% with respect to that of the reference N719-based device (8.20%).

Influence of alkoxy chain envelopes on the interfacial photoinduced processes in tetraarylporphyrin-sensitized solar cells

We have investigated the effect of the alkoxy chain length and nature on the reduction of dye-to-dye aggregation as well as on the enhancement of light harvesting capabilities.

Facile fabrication of thermally reduced graphene oxide–platinum nanohybrids and their application in catalytic reduction and dye-sensitized solar cells

We report the fast synthesis of thermally reduced graphene oxide : platinum (TRGO : Pt) nanohybrids by simply spraying a GO:Pt⁴⁺ solution on a hot plate.

Novel metal-free organic dyes possessing fused heterocyclic structural motifs for efficient molecular photovoltaics

Fused heterocyclic structural motifs possessing novel organic dyes have been synthesized as efficient sensitizers with a highest PCE of 8.08%.

Bilayer structured supramolecular light harvesting arrays based on zinc porphyrin coordination polymers for enhanced photocurrent generation in dye sensitized solar cells

Coordination polymers based on an acylhydrazone zinc porphyrin were synthesized and applied in dye sensitized solar cells for enhanced photocurrent generation.

N-Heterotriangulene chromophores with 4-pyridyl anchors for dye-sensitized solar cells

A series of N-heterotriangulenes decorated with 4-pyridyl anchors were synthesized and their performance in n-type TiO₂- and ZnO-based dye-sensitized solar cells investigated.

Porphyrins with intense absorptivity: highly efficient sensitizers with a photovoltaic efficiency of up to 10.7% without a cosensitizer and a coabsorbate

An indoline-conjugated porphyrin sensitizer achieves a photovoltaic efficiency of up to 10.7% in DSSCs without a cosensitizer and a coabsorbate.

Switching between porphyrin, porphodimethene and porphyrinogen using cyanide and fluoride ions mimicking volatile molecular memory and the ‘NOR’ logic gate

β-Substituted porphyrins were developed as a quantitatively operating “lab-on-a-molecule” for the detection of F⁻and CN⁻ions, by switching between porphyrin, porphodimethene and porphyrinogen along with distinct solution colour changes and reversibility.

Benefits of using BODIPY–porphyrin dyads for developing deep-red lighting sources

The syntheses, as well as the photophysical and electrochemical characterization, of two novel BODIPY–porphyrin dyads and their first application in lighting schemes are provided.

Novel porphyrin-preparation, characterization, and applications in solar energy conversion

Accelerated inner charge transfer in porphyrins promotes a broad light-harvesting ability up to 840 nm and a conversion efficiency of 9.2%.

Improved light absorbance does not lead to better DSC performance: studies on a ruthenium porphyrin–terpyridine conjugate

Despite having a good spectral response, a bis(tpy)ruthenium complex with peripheral porphyrin and phosphonate anchoring domains gives poor photoconversion efficiency due to a triplet–triplet energy transfer process.

Porphyrins Containing a Triphenylamine Donor and up to Eight Alkoxy Chains for Dye-Sensitized Solar Cells: A High Efficiency of 10.9%

Porphyrins are promising DSSC sensitizers due to their structural similarity to chlorophylls as well as their tunable strong absorption. Herein, a novel D-π-A porphyrin dye XW14 containing a strongly electron-donating triphenylamine moiety as the electron donor was designed and synthesized. To avoid undesirably decreased Voc caused by dye aggregation effect, two methoxy or hexyloxy chains were introduced to the para positions of the triphenylamine moiety to afford XW15 and XW16, respectively. To further extend the absorption to a longer wavelength, a benzothiadiazole unit was introduced as an auxiliary acceptor to furnish XW17. Compared with XW14, the introduction of additional methoxy or hexyloxy groups in XW15 and XW16 red-shift the onset wavelengths from 760 to 780 and 790 nm, respectively. More impressively, XW17 has a more extended π-conjugation framework, and thus, it exhibits a much broader IPCE spectrum with an extremely red-shifted onset wavelength of 830 nm, resulting in the highest Jsc (18.79 mA cm(-2)). On the other hand, the hexyloxy chains are favorable for suppressing the dye aggregation effect, and thus XW16 shows the highest Voc of 734 mV. As a result, XW16 and XW17 demonstrate photovoltaic efficiencies of 9.1 and 9.5%, respectively, higher than those of XW14 (8.6%) and XW15 (8.7%), and obviously higher than that of 7.94% for our previously reported dye, XW4. On the basis of optimized porphyrin dye XW17, we used a nonporphyrin dye with a high Voc and strong absorption around 500 nm (WS-5) as the cosensitizer to improve the Voc from 700 to 748 mV, with synergistical Jsc enhancement from 18.79 to 20.30 mA cm(-2). Thus, the efficiency was dramatically enhanced to 10.9%, which is among the highest efficiencies obtained for the DSSCs based on traditional iodine electrolyte. In addition, the DSSCs based on XW17 + WS-5 exhibit good photostability, which is beneficial for practical applications.

Application-oriented computational studies on a series of D-π-A structured porphyrin sensitizers with different electron-donor groups

A series of D-π-A zinc porphyrin sensitizers bearing a substituted iminodibenzyl group at the porphyrin meso position, which is expected to have different electron-donating abilities, were designed. Theoretical studies were performed to examine the photovoltaic properties of these molecules in dye-sensitized solar cells (DSSCs). In particular, the important concepts, the Fukui function and the extended condensed Fukui function, are employed to describe the electron-donating abilities accurately at the quantitative level. Tangui Le Bahers model was adopted to analyze charge transfer (CT) during electron transition. A correlation between the electron donating abilities of the derived iminodibenzyl group and CT was built to evaluate the cell performance based on sensitizers . The theoretical studies showed that porphyrins bearing an extremely strong electron-donating group (EDG) would fail in the generation of photocurrent in the closed circuit when applied in DSSCs due to the higher level of the HOMO energy than the redox potential of the redox couple (I(-)/I3(-)). The one with a weaker EDG () is expected to show better photovoltaic performance than porphyrin with an unsubstituted iminodibenzyl group. This study demonstrates a reliable method involving the employment of the Fukui function, the extended condensed Fukui function and the Tangui Le Bahers model for the evaluation of newly designed D-π-A type porphyrin sensitizers for use in DSSCs, and as guidance for future molecular design.

Synthesis, photophysical characterization, and photoelectrochemical evaluation of a palladium porphyrin sensitizer for TiO2-based dye-sensitized solar cells

An unsymmetrical (A3B) palladium porphyrin bearing a cyanoacrylic acid at one meso position has been synthesized for evaluation as a photosensitizer in dye-sensitized solar cells based on titanium dioxide ( TiO 2) as a comparison to other metalloporphyrins and as a proxy for other potential triplet-state photosensitizer compounds. The synthesis of this palladium porphyrin has provided new insight into the mechanism and product distribution of decarboxylative hydrolysis of malonic acid when attached at the porphyrin meso position. A crystal structure determination for a meso-formyl palladium porphyrin has been determined, showing saddle-distortion of the porphyrin core. The photophysical behavior of the palladium porphyrin sensitizer and its performance in photoelectrochemical cells are described and interpreted in the context of bimolecular excited state quenching pathways including oxygen sensitization, triplet–triplet annihilation and electron transfer events. Palladium porphyrins are proposed as a sensitizer class with potential for high efficiency dye-sensitized solar cells, but with the caveat that some overpotential for electron injection is necessary to compete against the multiple decay pathways that are specially available to triplet state photosensitizers.

Systematic Investigations on the Roles of the Electron Acceptor and Neighboring Ethynylene Moiety in Porphyrins for Dye-Sensitized Solar Cells

Cyanoacrylic and carboxyl groups have been developed as the most extensively used electron acceptor and anchoring group for the design of sensitizers for dye-sensitized solar cells. In terms of the photoelectric conversion efficiency, each of them has been demonstrated to be superior to the other one in certain cases. Herein, to further understand the effect of these two groups on cell efficiencies, a series of porphyrin sensitizers were designed and synthesized, with the acceptors systematically varied, and the effect of the neighboring ethynylene unit was also investigated. Compared with the sensitizer XW5 which contains a carboxyphenyl anchoring moiety directly linked to the meso-position of the porphyrin framework, the separate introduction of a strongly electron-withdrawing cyanoacrylic acid as the anchoring group or the insertion of an ethynylene unit can achieve broadened light absorption and IPCE response, resulting in higher Jsc and higher efficiency. Thus, compared with the efficiency of 4.77% for XW5, dyes XW1 and XW6 exhibit higher efficiencies of 7.09% and 5.92%, respectively. Simultaneous introduction of the cyanoacrylic acid and the ethynylene units into XW7 can further broaden light absorption and thus further improve the Jsc. However, XW7 exhibits the lowest Voc value, which is not only related to the floppy structure of the cyanoacrylic group but also related to the aggravated dye aggregation effect due to the extended framework. As a result, XW7 exhibits a relatively low efficiency of 5.75%. These results indicate that the combination of the ethynylene and cyanoacrylic groups is an unsuccessful approach. To address this problem, a cyano substituent was introduced to XW8 at the ortho position of the carboxyl group in the carboxyphenyl acceptor. Thus, XW8 exhibits the highest efficiency of 7.59% among these dyes. Further cosensitization of XW8 with XS3 dramatically improved the efficiency to 9.31%.

β-Functionalized Push-Pull Porphyrin Sensitizers in Dye-Sensitized Solar Cells: Effect of π-Conjugated Spacers

A series of new β-functionalized push-pull-structured porphyrin dyes were synthesized so as to investigate the effect of the π-conjugated spacer on the performance of dye-sensitized solar cells (DSSCs). Suzuki- and Heck-type palladium-catalyzed coupling methodologies were used to obtain various β-functionalized porphyrins and β-benzoic acid (ZnPHn) and β-vinylbenzoic acid (ZnPVn) derivatives from β-borylated porphyrin precursors. Photophysical studies of the resulting porphyrins revealed a clear dependence on the nature of the β linker. In particular, it was found that a β-vinylene linkage perturbs the electronic structure of the porphyrin core; this is less true for a β-phenyl linkage. Theoretical analyses provided support for the intrinsic intramolecular charge-transfer character of the β-functionalized, push-pull porphyrins of this study. The extent of charge transfer depends on the nature of the β-conjugated linkage. The photovoltaic performances of the cells sensitized with β-phenylenevinylene ZnPVn exhibited higher power conversion efficiency values than those bearing β-phenyl linkages (ZnPHn). This was ascribed to differences in light-harvesting efficiency. Furthermore, compared to the use of a standard iodine-based electrolyte, the DSSC performance of cells made from the present porphyrins was improved by more than 1 % upon using a cobalt(II/III)-based electrolyte. Under standard AM 1.5 illumination, the highest efficiency, 8.2 %, was obtained by using cells made from the doubly β-butadiene-linked porphyrin.