New Donor-π-Acceptor Type Triazatruxene Derivatives for Highly Efficient Dye-Sensitized Solar Cells

Tandem dye-sensitized solar cells achieve 12.89% efficiency using novel organic sensitizers

This study presents a significant advancement in tandem dye-sensitized solar cells (T-DSSCs) through the strategic synthesis of novel triazatruxene (TAT) sensitizers MS-1 and MS-2. These organic sensitizers demonstrate exceptional light-harvesting capacity and overall performance, pushing the boundaries of power conversion efficiency (PCE) in DSSCs. The MS-1-based DSSCs achieved an impressive PCE of 12.81%, while MS-2 sensitizers reached a notable 10.92%. These efficiencies represent significant improvements over the conventional N719 dye (7.60%), demonstrating the potential of metal-free organic sensitizers in DSSC technology. The key to these noteworthy results lies in the molecular design of the organic sensitizers. The triazatruxene donor segment in the MS-1 and MS-2 dyes, featuring a rigid structure and efficient intramolecular charge transfer (ICT), proved to be a game-changer for photovoltaic properties. Building on these results, we explored an innovative parallel tandem cell (PT-DSSC) configuration. By connecting separate cells containing N719 and MS-1 sensitizers, we achieved a record efficiency of 12.89% with enhanced short-circuit current density (JSC) and open-circuit voltage (VOC)compared to single-dye cells. This study highlights the potential of molecular engineering in organic sensitizers and device optimization to enhance DSSC performance, paving the way for further advancements in solar cell technology.

6-Aminocoumarin-derived Schiff base gelators: aggregation and sensing of CN-, Fe3+, Cu2+ and CO2 under different conditions

Herein, we report the synthesis, characterization, supramolecular gelation and multiple applications of 6-aminocoumarin-derived Schiff bases 1 and 2. Both Schiff bases underwent gelation in DMF-H2O (2 : 1, v/v), DMSO-H2O (2 : 1, v/v) and dioxane-H2O (2 : 1, v/v) involving weak forces. Furthermore, the gels were stable and exhibited good viscoelastic properties. The storage modulus (G') of each gel was considerably higher than its loss modulus (G''). The higher value of the crossover point and lower value of tan δ for the gel of Schiff base 2 compared to the gel of Schiff base 1 demonstrated the better gelation behaviour of 2 than that of 1 in DMF-H2O (2 : 1, v/v). Further, iodo-analogue 2 exhibited cross-linked helical morphology, whereas non-iodo analogue 1 exhibited long chain fibrous morphology, as observed via FESEM. These differences in morphology and viscoelastic behaviors were attributed to the iodo group present in 2, which influenced its aggregation involving halogen bonding. To demonstrate their application, the DMF-H2O (2 : 1, v/v) gels of both 1 and 2 recognized CN- over a series of other anions by exhibiting a gel-to-sol phase change. Besides anion sensing, gels 1 and 2 selectively detected Fe3+ and Cu2+ ions over other metal ions via a gel-to-gel colour change. Finally, CN--treated solutions of 1 and 2 allowed the successful detection of CO2 by the naked eye. Moreover, the detection was possible using a test-kit method.

Simple Functionalization of a Donor Monomer to Enhance Charge Transfer in Porous Polymer Networks for Photocatalytic Hydrogen Evolution

Porous polymer networks (PPNs) are promising candidates as photocatalysts for hydrogen production. Constructing a donor-acceptor structure is known to be an effective approach for improving photocatalytic activity. However, the process of how a functional group of a monomer can ensure photoexcited charges transfer and improve the hydrogen evolution rate (HER) has not yet been studied on the molecular level. Herein, we design and synthesize two kinds of triazatruxene (TAT)-based PPNs: TATR-PPN with a hexyl (R) group and TAT-PPN without the hexyl group, to understand the relationship between the presence of the functional group and charge transfer. The hexyl group on the TAT unit was found to ensure the transfer of photoexcited electrons from a donor unit to an acceptor unit and endowed the TATR-PPN with stable hydrogen production.

From truxenes to heterotruxenes: playing with heteroatoms and the symmetry of molecules

As a result of the modification of truxene, we can change the electronic structure or create multidimensional materials. Thus, the use of truxenes is very wide.

Functionalization at Nonperipheral Positions of Triazatruxene: Modular Construction of 1,6,11-Triarylated-Triazatruxenes for Potentially Organic Electronics and Optoelectronics

Functionalization from nonperipheral positions of triazatruxene is representing a challenge. Triarylation of the nonperipheral positions (1, 6, and 11) in triazatruxene scaffold has been achieved for the first time via two approaches. The transformations involve arylation/cyclotrimerization and cyclotrimerization/arylation sequences. POCl₃-mediated direct cyclotrimerization of oxindoles containing electron-deficient substituents on the aryl group at the C7-position resulted in the formation of 2-chloroindoles, whereas oxindoles containing electron-donating substituents gave the triazatruxenes. Furthermore, desired triazatruxenes were achieved through cyclotrimerization of 7-bromooxindole followed by coupling with arylboronic acids. NMR structural analysis exhibited that two of the suitably substituted oxindole and triazatuxene may have atropisomerism at room temperature. As a representative triazatruxene scaffold, the optoelectronic properties of 9a have also been studied via ultraviolet-visible (UV-vis) absorption spectra and fluorescence spectra of 9a thin films. Also, density functional theory calculation was realized to get knowledge about frontier molecular orbitals. In the light of the information obtained, an organic light-emitting diode (OLED) device utilizing 9a as an emissive layer was applied to obtain white emission. In brief, this study provides the first examples of the synthesis of triazatruxenes bearing aryl substituents at the nonperipheral positions as candidate compounds for organic electronics, optoelectronics, and material chemistry.

Synthesis, Structure, and Chiroptical Properties of Indolo- and Pyridopyrrolo-Carbazole-Based C2 -Symmetric Azahelicenes

Treatment of 11,12-bis(1,1'-biphenyl-3-yl or 6-phenylpyridin-2-yl)-substituted 11,12-dihydro-indolo[2,3-a]carbazole with an oxidizing system of Pd(II)/Ag(I) induced effective double dehydrogenative cyclization to afford the corresponding π-extended azahelicenes. The optical resolutions were readily achieved by a preparative chiral HPLC. It was found that the pyridopyrrolo-carbazole-based azahelicene that contains four nitrogen atoms exhibits ca. 6 times larger dissymmetry factors both in circularly dichroism (CD) and circularly polarized luminescence (CPL), |g_CD | and |g_CPL | values being 1.1×10^-2 and 4.4×10^-3 , respectively, as compared with the parent indolocarbazole-based azahelicene. Theoretical calculations at the RI-CC2 level were employed to rationalize the observed enhanced chiroptical responses. The (chir)optical properties of the former helicene was further tuned by a protonation leading to remarkable red-shift with a considerable enhancement of the |g_CPL | value.

Naphthalimide-decorated imino-phenol: supramolecular gelation and selective sensing of Fe3+ and Cu2+ ions under different experimental conditions

Compound 1 forms gels in DMF–H₂O (1 : 1, v/v) and DMSO–H₂O (1 : 1, v/v). While it was insensitive to any metal ion in DMF–H₂O, the gel state was responsive to Fe³⁺ over the other metal ions studied. In CH₃CN or aqueous CH₃CN compound 1 senses Cu²⁺ ion.

Influence of the heteroatom introduction on the physicochemical properties of 5-heterotruxenes containing nitrogen, oxygen and sulfur atom

5-heterotruxenes are a class of heterocyclic aromatic compounds derived from the parent heptacyclic hydrocarbon, namely truxene. Currently, few substances belonging to this group are known. These include derivatives of 5-oxatruxene, 5-azatruxene, and 5-thiatruxene, along with its sulfone and sulfoxide. The introduction of one heteroatom, not only enables selective monofunctionalization of the 5-heterotruxene system but also allows adjustment of physico-chemical properties depending on the needs. Two investigated compounds, namely 5-oxatruxene and 5-azatruxene, exhibit fluorescence enhancement by symmetry breaking (FESB) phenomena, manifested by a fourfold increase in the fluorescence quantum yield. Therefore, derivatives of 5-heterotruxenes may contribute to the development of new stable optoelectronic substances as well as other functional materials. Nevertheless, in the beginning, it is crucial to investigate their spectral, thermal, and electrochemical properties to learn more about the advantages and limitations of these aromatic systems. The following article also presents a new simplified and universal synthetic methodology, without use of anhydrous conditions or organometallic substances, giving easy access to 5-azatruxene and structural-related heteroaromatic systems. The discussed heteroatom influence is not limited to the truxene core but also helps to understand the physicochemical properties of other, currently top-rated high-symmetric heteroaromatic systems such as circulenes, sumanenes and their analogues.

Molecular engineering of anchoring groups for designing efficient triazatruxene-based organic dye-sensitized solar cells

Triazatruxene with designed anchoring groups provides better photovoltaic activities.

Effects of ethynyl unit and electron acceptors on the performance of triazatruxene-based dye-sensitized solar cells

Effects of ethynyl unit and electron acceptors/anchors on the photovoltaic performance of triazatruxene-based organic dyes were systematically investigated.

Monothiatruxene: a new versatile core for functional materials

A monothiatruxene and its oxidized and/or brominated derivatives were prepared through an efficient route.

Benzotrifuran (BTFuran): a building block for π-conjugated systems

Reported here is the first synthesis, X-ray crystal structure, and derivatization of C_3h-symmetric benzotrifuran (BTFuran), oxygen analog of the widely exploited benzotrithiophene.

Triazatruxene radical cation: a trigonal class III mixed valence system

The highly symmetric and stable triazatruxene radical cation was generated chemically for the first time.

Bi-anchoring Organic Dyes that Contain Benzimidazole Branches for Dye-Sensitized Solar Cells: Effects of π Spacer and Peripheral Donor Groups

Benzimidazole-branched bi-anchoring organic dyes that contained triphenylamine/phenothiazine donors, 2-cyanoacrylic acid acceptors, and various π linkers were synthesized and examined as sensitizers for dye-sensitized solar cells. The structure-activity relationships in these dyes were systematically investigated by using absorption spectroscopy, cyclic voltammetry, and density functional theory calculations. The wavelength of the absorption peak was more-heavily influenced by the nature of the π linker than by the nature of the donor. For a given donor, the absorption maximum (λmax ) was red-shifted on changing the π linker from phenyl to 2,2'-bithiophene, whilst the dyes that contained triphenylamine units displayed higher molar extinction coefficients (ϵ) than their analogous phenothiazine-based triphenylamine dyes, which led to good light-harvesting properties in the triphenylamine-based dyes. Electrochemical data for the dyes indicated that the triphenylamine-based dyes possessed relatively low-lying HOMOs, which could be beneficial for suppressing back electron transfer from the conduction band of TiO2 to the oxidized dyes, owing to facile regeneration of the oxidized dye by the electrolyte. The best performance in the DSSCs was observed for a dye that possessed a triphenylamine donor and 2,2'-bithiophene π linkers. Electron impedance spectroscopy (EIS) studies revealed that the use of triphenylamine as the donor and phenyl or 2,2'-bithiophene as the π linkers was beneficial for disrupting the dark current and charge-recombination kinetics, which led to a long electron lifetime of the injected electrons in the conduction band of TiO2 .

Shedding light on hydroxyquinoline-based ruthenium sensitizers with a long-lived charge carrier to boost photocatalytic H2 evolution

Three new hydroxyquinoline-coordinated ruthenium(ii) sensitizers bearing a polypyridyl derivative anchor (R1, R2 and R3) were synthesized that could tether to visible light sensitization over a Pt–TiO₂ system for hydrogen production.

Photophysical properties of octupolar triazatruxene-based chromophores

The intramolecular charge transfer properties of tribranched chromophores related to their TPA properties are explored by estimating the TPA essential factors.

AIE active triphenylamine–benzothiazole based motifs: ESIPT or ICT emission

AIE active triphenylamine–HBT chromophores were synthesized via Suzuki coupling reaction and their emission properties due to ESIPT or ICT phenomena were investigated.

First Study on Phosphonite-Coordinated Ruthenium Sensitizers for Efficient Photocatalytic Hydrogen Evolution

For the first time we report the design and syntheses of phosphonite coordinated ruthenium(II) sensitizers bearing ĈN̂N ligand and/or terpyridine derivatives carboxylate anchor (GS11, GS12. and GS13) and its application for hydrogen production over Pt-TiO2 system. These heteroleptic complexes exhibit broad metal-to-ligand charge transfer transition band over the whole visible regime extending up to 900 nm. DFT calculations of these complexes show that the HOMO is distributed over the Ru and Cl atom whereas; LUMO is localized on the polypyridile ligand, which are anchored on TiO2 surface. Among the sensitizers tested for photocatalytic hydrogen evolution, GS12 exhibited a maximum turnover number (TON) 8605 (for 8 h), which is very high compared to the reference sensitizer (N719) with TON 163 under similar evaluation condition. The dependence of the hydrogen evolution rate at different pH using GS11, GS12, GS13, and DX-1-sensitized Pt-TiO2 has been studied and the maximum H2 production yield was obtained at pH 7 for all sensitizers.

Benzo[a]carbazole-Based Donor-π-Acceptor Type Organic Dyes for Highly Efficient Dye-Sensitized Solar Cells

A novel class of metal-free organic dyes based on benzo[a]carbazole have been designed, synthesized, and used in dye-sensitized solar cells for the first time. These types of dyes consisted of a cyanoacrylic acid moiety as the electron acceptor/anchoring group and different electron-rich spacers such as thiophene (JY21), furan (JY22), and oligothiophene (JY23) as the π-linkers. The photophysical, electrochemical, and photovoltaic properties, as well as theoretical calculations of these dyes were investigated. The photovoltaic performances of these dyes were found to be highly relevant to the π-conjugated linkers. In particular, dye JY23 exhibited a broad IPCE response with a photocurrent signal up to about 740 nm covering the most region of the UV-visible light. A DSSC based on JY23 showed the best photovoltaic performance with a Jsc of 14.8 mA cm(-2), a Voc of 744 mV, and a FF of 0.68, achieving a power conversion efficiency of 7.54% under standard AM 1.5 G irradiation.

Tri(N-carbazolyl)triphenylamine-based starburst organic dyes: effects of different acceptors on the optical, electrochemical and photovoltaic properties

Novel tri(N-carbazolyl)triphenylamine-based organic dyes were designed, synthesized and applied as photosensitizers for DSSCs.

A meso–meso directly linked porphyrin dimer-based double D–π–A sensitizer for efficient dye-sensitized solar cells

A novel double D–π–A branched dye (JY07) was synthesized and applied as a sensitizer for DSSCs.

Biindole-based double D–π–A branched organic dyes for efficient dye-sensitized solar cells

Novel biindole-based double D–π–A branched organic dyes have been designed and synthesized for dye-sensitized solar cells.