Auxiliary Donor Research Articles

Slow Magnetic Relaxation in a Dysprosium Metallocene Complex Bearing Equatorial DyIII−P Bonds

AbstractSingle molecule magnets (SMMs) containing dysprosium‐phosphorus bonding are rare due to great challenges in constructing the bonding between hard lanthanide ions and soft phosphorus donors. Here we successfully isolated a novel mononuclear bis‐Cp* dysprosium compound, Cp*2Dy[η‐CH(PPh2)2]⋅C7H8 (1‐Dy), via the salt metathesis reactions of Cp*2Dy(BPh4) and K[(PPh2)2CH] in THF (Cp*=pentamethylcyclopentadienyl). The magnetic investigations indicate its strong SMM behavior evidenced by the open magnetic hysteresis loops below 6 K and the high effective barrier of 300 cm−1. This could be ascribed to weak dative DyIII−P bonds at equatorial sites in such [Cp2DyX]‐type (X=auxiliary donors) complexes.

Novel Indolenine-Based hemicyanine dyes with extended π-Linker and auxiliary donor as potential Photosensitizers: Synthesis, Photophysical, electrochemical and computational Insights

Three novel hemicyanine dyes, D1-D3, were synthesized successfully based on dimethylaniline (DMA) and TPA donors and a carboxylated indolium vinyl acceptor linked through benzene unit as an extended π-spacer or through PTZ unit as an auxiliary donor to form the D1-π-A, D2-π-A & D2-D3-A systems, respectively. A multi-step process was conducted to yield the desired donor and acceptor intermediates. These were finally coupled through the Suzuki-Miyaura coupling and Knoevenagel condensation reactions to obtain the desired target dyes. A panchromatic response and a bathochromic shift of the ICT band maxima in the visible region were observed with the lowest band gap energy, Eg = 1.71 eV and λabs., max. = 590 nm, given by dye D3, were attributed to the presence of the auxiliary donor, PTZ. However, due to the high coplanarity of dye D1 it showed the highest absorptivity value of ε = 36462 M−1cm−1. The HOMO and LUMO levels are within the range suitable for smooth dye regeneration and electron ejection, EHOMO = -5.37 to −5.18 eV, and ELUMO = -3.47 to −3.27 eV. The density functional theory (DFT) and time-dependent TD-DFT at the B3LYP/6-31G(d,p) level were conducted to explore the bridged effect on geometric and TD-BHandH/6-31G(d,p) for optoelectronic properties.

Synergistic charge-transfer dynamics of novel D-D-A-π-A framework containing indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers: from structural engineering to performance metrics in photovoltaic solar cells.

Dye-sensitized solar cells (DSSCs) present a convincing substitute for conventional silicon-based solar cells because of their possible lower manufacturing costs and versatile uses. Electron injection and dye regeneration processes are important in meeting the need for photosensitizers with improved efficiency and stability. Aimed at enhancing the performance and efficiency of DSSCs, this study focuses on the structural engineering to performance metrics of novel indoline-benzo[d][1,2,3]thiadiazole based push-pull sensitizers (LHZ1 to LHZ9) with D-D-A-π-A framework. The current study provides insights into the photovoltaic and optoelectronic properties of the investigated dyes, which are significantly influenced by the modification of auxiliary donors (D), internal acceptors with thiophene as a spacer, and cyanoacrylic acid (A) as the terminal acceptor. These modifications enhance rapid charge transfer among the dyes, highlighting the critical role of dye-semiconductor interactions. The suitability of developed sensitizers for DSSCs applications is confirmed by executing quantum methods like NBO, TDM, FMO, DOS, Eb, ΔGreg, ΔGinject, VRP, and ICT parameters qCT (e-), DCT ( ), H index ( ), ∆( ), t index ( ), and μCT (D). All of the investigated dyes have HOMO levels lower than the electrode I-/I3-'s redox potential (-4.8 eV) and LUMO values that are appropriately higher than the conduction band of TiO2 (-4.0 eV). The novel dyes showed a closing of the energy gap (2.38-1.84 eV). The LHZ7 and LHZ8 molecules with the lowest Eg (1.97 eV and 1.84 eV) demonstrated the highest absorption (up to 746 nm > 402 nm for LHZ), which was caused by the insertion effect of varied donors and internal acceptors. Almost all photosensitizers appeared with remarkable properties, i.e., red-shifted absorption maxima (746 nm), lowest Ex (1.66 eV), Eb (0.02 eV), and highest values of LHE (0.958). The TDM analysis revealed high charge density on HOMO of donor and LUMO of acceptors in designed dyes. DOS analysis revealed that the donor parts of the molecules delocalized the highest occupied molecular orbitals of dye particles. The electronic properties predicted by the NBO analysis showed that donor groups donate high and faster transfer of charge, and internal acceptor groups rapidly accept them. The electron injection (ΔGinject) and dye regeneration (ΔGreg) analysis of photosensitizers attached with TiO2 proved efficient charge transfer properties from the donor of newly designed dyes onto the conduction band of TiO2. This study, also supported by the thermodynamic stability of dyes with negative values of Gibbs free energy, revealed that the performance of the designed dyes is augmented by modifying the donor and internal acceptors of the reference photosensitizer for effective application in the experimental community. All of the dyes are suitable for DSSCs based on the calculated parameters. Still, the LHZ9 dye proved proficient in applying dye-sensitized solar cells due to its remarkable properties, i.e., lowest gap and red-shifted absorption maxima.

Metal-free phenothiazine dyes with alkoxy chains modified at different position for dye-sensitized solar cells

Long alkyloxy or alkoxyphenyl chains are commonly introduced to organic dye sensitizers in dye-sensitized solar cells (DSSCs) to inhibit the aggregation of sensitizer on the TiO2, thereby minimizing charge recombination. Here, we synthesized four D-D-π-A sensitizers (TP-C6, TP-PhOC6, C6O-TP-C6, C6O-TP-PhOC6), that feature alkyl-/alkoxyphenyl- moiety in phenothiazine (PTZ) donor’s N-position, and either alkoxy or no alkoxy groups in triphenylamine (TPA) auxiliary donor. Then, their photophysical, electrochemical and DSSCs properties were investigated. The UV-Vis and electrochemical studies revealed that all four dyes exhibited good light absorption ability and appropriate HOMO-LUMO energy levels. The introduction of alkoxy at the donor or auxiliary donor can result in a significant redshift in absorption. Among them, TP-PhOC6, which incorporates an alkoxy phenyl group at the N-position of PTZ and lacks alkoxy in TPA, induces a greater redshift in ICT absorption with strong absorption intensity. Additionally, in TP-PhOC6 based DSSC, mitigated charge recombination was observed. As a result, this device exhibited the strongest and widest IPCE spectrum, the highest Jsc (12.77 mA/cm²) and Voc (0.85 V), leading to the highest PCE (6.59 %).

Exploring the ON/OFF nonlinear optical (NLO) response in tetracene-based chromophores: A DFT study on solvent and frequency-dependent NLO properties for switching applications

Tetracene-based nonlinear optical (NLO) materials are an ambient field of interest in optoelectronic technology. Inspired by this material, we theoretically designed D-D-A framework molecules (ZO and ZO-1 to ZO-16) with auxiliary donor and acceptor screening of solo tetracene linear surface and investigated their reactivity, electrical properties, solvent-dependent optical and ON/OFF NLO properties utilizing DFT simulations. The CPCM and IEFPCM model is used to examine how entire spectrum of medium polarity, ranging from less polar to more polar solvents (chloroform (ε = 4.71) < tetrahydrofuran (ε = 7.43) < DMSO (ε = 46.83 < water (ε = 78.36)) affect the optical absorption and NLO characteristics (βtot, αtot, and μtot) of suggested compounds (ZO and ZO-1 to ZO-16). Furthermore, natural bond orbital analysis (NBO) and topological analysis (MEP, ELF, and LOL) were used to explain the NLO results. Regarding the charge transfer robustness, ZO-9, a promising tetracene derivative, is identified as an appealing second-order NLO candidate, with the lowest energy gap (1.642 eV) and largest λmax (546.692 nm) among all investigated derivatives. Moreover, the solvent-dependent optical absorption spectrum shows that polar solvent (THF) alleviates the λmax from 273.081 nm to 707.511 nm in ZO-11. Similarly, solvent also influences the NLO properties in all designed compounds, especially in ZO-9, which displayed giant βtotal = 7.244 × 105 in chloroform, 8.640 × 105 in THF, 1.153 × 106 in DMSO, and 1.180 × 106 in water as well as in gas (1.993 × 105). Additionally, the results of the second harmonic generation (SHG) β(−2ω, ω, ω) and the electro-optical Pockels effect (EOPE) β(−ω,ω,0) computed at the frequencies of ω = 1064 nm (0.0428 au) and ω = 532 nm (0.0856 au) validates that all tetracene based derivatives are excellent NLO candidates for laser working condition and switching applications.

Excited State Proton Transfer from Acidic Alcohols to a Quinoline Photobase Can Be Solvated by Non-Acidic Alcohol Solvents.

Photobases are a type of molecule that become more basic upon photoexcitation and can therefore be used to control proton transfer reactions with light. The solvation requirements for excited state proton transfer (ESPT) in photobase systems is poorly understood, which limits their applicability. Here, we investigate the solvation of the ESPT reaction using 5-methoxyquinoline (MeOQ), a well-studied photobase with an excited state pKa (pKa*) of approximately 15.1, as a model system. Previous studies have shown that, in addition to the acidic donor that donates a proton to the photoexcited MeOQ, an additional "auxiliary donor" is necessary to solvate the resulting alkoxide. We investigate whether a nonacidic hydrogen bond donor (an alcohol solvent that MeOQ cannot deprotonate in bulk) can act as the auxiliary donor for the MeOQ ESPT reaction. First, we use steady state spectroscopy, TCSPC, and electronic structure calculations to show that MeOQ can deprotonate the acidic donor 2,2,2-trifluoroethanol (TFE, pKa = 12.5) using ethanol as the auxiliary donor. We show that the degree of ESPT is largely predicted by the degree of ground state hydrogen bonding between the photobase and the acidic donor. Next, we study the deprotonation of the acidic donors TFE and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP, pKa = 9.3) with MeOQ in a variety of nonacidic alcohol solvents of varying chain length and branching. MeOQ ESPT occurs to varying extents in all solvents, suggesting that all studied nonacidic alcohols can function as auxiliary donors. We show that the concentration of the acidic donor is strongly correlated with the degree of ESPT. These results are necessary fundamental steps toward the understanding of the photobase ESPT reaction and its wide application in a variety of chemical systems.

Theoretical study on the efficiency of new organic dyes based on (E)-2-(2-(thiophen-3-yl)vinyl)-1,1′-bipyrrole as dye-sensitized solar cell sensitizers

Dye-sensitized solar cells (DSSCs) have gained critical importance as a leading emerging photovoltaic technology for low-cost power generation due to their simple production, light weight, applicability to the development of flexible photovoltaic devices, and use of abundant and inexpensive materials, including advantageous metal-free organic dyes. In this context, as a continuation of our work on DSSCs, a theoretical examination using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) was conducted to evaluate the photovoltaic performance of eight new organic dyes. Each dye contains an electron donor group ((E)-2-(2-(thiophen-3-yl)vinyl)-1,1′-bipyrrole), an electron acceptor group (cyanoacrylic acid (CCA)), and four auxiliary donor/acceptor groups, i.e., 3,4-ethylenedioxythiophene (EDOT), furan/benzothiadiazole (BTZ), diketopyrrolopyrrole (DPP) linked to π-conjugated bridges such as styrene or thiophene. We calculated several parameters for each dye, including EHOMO, ELUMO, Egap, λmax, Eex, pen-circuit photovoltage (VOC), light harvesting efficiency (LHE), regeneration driving force (ΔGreg), electron injection driving force (ΔGinject), and excitation lifetime (τ) to determine the photovoltaic efficiency of each dye. The results showed that the new dyes exhibited good performance and remarkable energy-conversion efficiencies. Additionally, all investigated dyes posed as promising candidates for the generation of effective DSSC sensitizers, particularly M6, which contained a styrene-linked EDOT auxiliary donor group.

An unprecedented roll-off ratio in high-performing red TADF OLED emitters featuring 2,3-indole-annulated naphthalene imide and auxiliary donors

The annulation of an NMI scaffold at positions 3 and 4 with indole, which has a set of twisted electron-rich substituents at its periphery, allows for the development of high-performance and persistent red-TADF OLED emitters.

Nickel-decorated graphite phase carbon nitride photocatalysts coupled with carbazole-based calixarene dyes for high-efficiency visible light-driven hydrogen evolution

The development of artificial devices that mimic the highly efficient and sophisticated photosystems found in nature is a subject worthy of in-depth study. Two calixarene D-π-A dyes, C4-CZSTP and C4-CZBTP, containing an N-methylcarbazole group as a secondary auxiliary electron donor, are synthesized on the basis of our previously reported calixarene dye C4-BTP. These dyes are then cooperated with Ni-deposited g-C3N4 to prepare ternary photocatalysts, denoted as C4-CZSTP/Ni/g-C3N4, C4-CZBTP/Ni/g-C3N4 and C4-BTP/Ni/g-C3N4, and their photocatalytic performances are evaluated under visible light irradiation. The optimized 4.0 wt% C4-CZSTP/Ni/g-C3N4 sample gives a remarkable H2 evolution rate of 5552 μmol g−1 h−1, representing one of the highest records among the reported analogous systems based on g-C3N4. And after an extended test of 49 h, a total H2 yield of 63.57 mmol g−1 is obtained, corresponding to a turnover number (TON) based on C4-CZSTP moles (TONC4-CZSTP) of 3180. This performance can be attributed to the enhanced light-harvesting and photoelectron conversion of the as-prepared calixarene dyes, the adjusted energy levels and the effective cooperation of the three components. The optimal performance of C4-CZSTP/Ni/g-C3N4 among the three dye-sensitized systems is due to its higher lowest unoccupied molecular orbital (LUMO) value, i.e. stronger electronic driving force from the excited dye to g-C3N4. This study provides an interesting example for the design and preparation of a low-cost, high-efficiency and noble metal-free photocatalytic system for solar fuel production.

Diphenylpyrrole-Strapped Calix[4]pyrrole Extractant for the Fluoride and Chloride Anions.

The anion binding features of diphenylpyrrole-strapped calix[4]pyrrole 1 have been investigated by means of 1 H NMR spectroscopy and ITC (isothermal titration calorimetry), as well as single crystal X-ray diffraction analyses. Receptor 1 bearing an auxiliary pyrrolic NH donor and solubilizing phenyl groups on the strap was found to bind F- , Cl- , and Br- as their tetrabutylammonium salts with high affinity in DMSO-d6 . In addition, receptor 1 was found to extract the fluoride anion (as both its tetraethylammonium (TEA+ ) and tetrabutylammonium (TBA+ ) salts), as well as the chloride anion into chloroform-d from an aqueous source phase. Cation metathesis using TBAI or the use of a dual host approach involving crown ethers enabled receptor 1 to extract simple alkali metal fluoride or chloride salts from water. Quantitative binding of NaF by receptor 1 was observed in 20 % D2 O-DMSO-d6 allowing for the direct determination of the NaF concentration in an unknown sample.

A Theoretical Investigation of Decorated Novel 1,2-Di(4-pyridyl)-ethylene based Dye Sensitized Solar Cells (DSSC)

Density functional theory (DFT) approaches are employed to investigate the performance of dyes and the influence of p-conjugation in dye-sensitized solar cells (DSSCs). In this investigation, five new 1,2-di(4-pyridyl)-ethylene based conjugated donor-π-acceptor organic dyes (D-π-A) exist. The spacer is a diphenylamine (DPA) group, while the diphenyl amine group serves as the component that donateselectrons in each system, the nitro/cyano group is used as an electron accepting group. An alternate methyl/ethyl group is employed as π-conjugated spacer in order to study the effect of the auxiliary donor group. Through performing DFT calculations with the B3LYP both the polarized split-valence 6-311++G (d,p) basis sets, an excitation energies, absorption spectra and emission spectra of eachmolecule were examined. The polarizable continuum model (PCM) is utilized in studying these impact for solvent. The energies at which these dyes are LUMO and HOMO, which assure the favourable impact for electron injection and these dye regeneration process. The calculation of the HOMO-LUMO gap demonstrates good agreement when compared to spectral information. The light-harvestingefficiency (LHE), electron injection free energy (ΔGinject), as well as oscillator strength (f) are computed and explained. The calculated open-circuit photovoltage values (Voc) and electron coupling constant (VRP) for the studied dye-sensitizers are also included in this study.

Facile Functionalization of Ambipolar, Nitrogen-Doped PAHs toward Highly Efficient TADF OLED Emitters.

Despite promising optoelectronic features of N-doped polycyclic aromatic hydrocarbons (PAHs), their use as functional materials remains underdeveloped due to their limited post-functionalization. Facing this challenge, a novel design of N-doped PAHs with D-A-D electronic structure for thermally activated delayed fluorescence (TADF) emitters was performed. Implementing a set of auxiliary donors at the meta position of the protruding phenyl ring of quinoxaline triggers an increase in the charge-transfer property simultaneously decreasing the delayed fluorescence lifetime. This, in turn, contributes to a narrow (0.04-0.28 eV) singlet-triplet exchange energy split (ΔEST) and promotes a reverse intersystem crossing transition that is pivotal for an efficient TADF process. Boosting the electron-donating ability of our N-PAH scaffold leads to excellent photoluminescence quantum yield that was found in a solid-state matrix up to 96% (for phenoxazine-substituted derivatives, under air) with yellow or orange-red emission, depending on the specific compound. Organic light-emitting diodes (OLEDs) utilizing six, (D-A)-D, N-PAH emitters demonstrate a significant throughput with a maximum external quantum efficiency of 21.9% which is accompanied by remarkable luminance values which were found for all investigated devices in the range of 20,000-30,100 cd/m2 which is the highest reported to date for N-doped PAHs investigated in the OLED domain.

New green emitters based on push-pull type pyrene substituted cyanopyridones: Design strategies and utilization in organic light-emitting diodes

A novel series of D-A-D type conjugated dyes (Py-CyP1-7) centred on a strongly electron-withdrawing cyanopyridone scaffold (A) linked to highly electron-donating pyrene unit (D) and varied auxiliary donors (D) were designed and synthesized, for applications in green organic light-emitting diodes (OLEDs). All the hybrids were systematically subjected to theoretical, optical, electrochemical, and thermal studies to validate their efficiency in behaving as green emitters. Finally, we employed the dyes as sole and dopant emitters in OLEDs. The OLED with 3 wt % Py-CyP4 in the CBP host shows maximum efficiencies of 14.38 cd A−1, 12.04 lm W−1, and 5.91%.

Effect of the spatial configuration of donors on the photovoltaic performance of co-adsorbent organic dyes formed by Z/E configuration

Molecular modification is an important pathway to explore the highly efficient dyes for dye sensitized solar cells (DSSCs). In this work, three co-adsorbent D-π-A dye sensitizers (L1, L2 and L3) formed by Z/E configuration were prepared by the introduction of 4-methoxyphenyl group into the olefin containing triphenylamine dyes, and their photo-physical absorption, electrochemical properties and photovoltaic performance were systematically investigated. Density functional theory (DFT) calculations have been employed to gain insight into the optimized molecular configuration and electron distribution of dyes L1, L2 and L3, which are further correlated with the experimental results. The results indicated that the 4-methoxyphenyl auxiliary donor brought a molecular Z/E configuration and more electron injection capability, which is beneficial to the prevention of π-π aggregation and good light-capturing capability. The photo-physical absorptions are obviously red-shifted from 441 nm to 451 nm for dye L1 and 462 nm–492 nm for dye L2 compared with their predecessors. Co-adsorbent dye L3 with a cyclic thiourea functionalized triphenylamine donor afforded significantly improved current density (15.83 mA cm−2) and PCE (7.96%).

Design of a D–Di–π–A Architecture with Different Auxiliary Donors for Dye‐Sensitized Solar Cells: Density Functional Theory/Time‐Dependent‐Density Functional Theory Study of the Effect of Secondary Donors

AbstractIn this work, five novel D–Di–π–A molecules based on ethoxy donor moiety are designed from the reference molecule R to optimize the photovoltaic performance of dye‐sensitized solar cell (DSSC) systems. The geometrical, electronic, optical, and photovoltaic characteristics of the D1–D5 compounds are analyzed. D1–D5 show band gaps (Egap) in the range of 2.13–2.25 eV with the maximum absorption wavelength (λabs) in 427–451 nm. Charge transport characteristics are examined by employing frontier molecular orbitals and density of states. The transition density matrix is employed to predict the characteristics of the electronic excitation mechanisms and the localization of the electronic holes betwixt the donor and acceptor moieties. The data obtained indicate that adding the various auxiliary donors to dye (R) facilitate its electron injection and improve the impact of intramolecular charge‐transfer (ICT), which lead to a red‐shifted absorption. The open‐circuit voltage (Voc) data obtained from theoretical computations vary from 1.26 to 1.30 eV, while the data for the light harvesting efficiency range from 0.97 to 1.00. Indeed, this study may help chemists to synthesize efficient dyes for DSSC.

The Impact of TPA Auxiliary Donor and the π-Linkers on the Performance of Newly Designed Dye-Sensitized Solar Cells: Computational Investigation.

The efficiency of the newly designed dye-sensitized solar cells (DSSCs) containing triphenylamine, diphenylamine (TPA), phenothiazine, and phenoxazine as donors and triazine, phenyl with D1-D2-π-linker-π-(A)2 architecture has been investigated using density functional theory (DFT) and time-dependent (TD-DFT) methods. These methods were used to investigate the geometrical structures, electronic properties, absorption, photovoltaic properties, and chemical reactivity. Furthermore, the calculated results indicate that different architectures can modify the energy levels of HOMO and LUMO and reduce the energy gap. The absorption undergoes a redshift displacement. This work aims at calculating the structural geometries and the electronic and optical properties of the designed dyes. Furthermore, the dye adsorption characteristics, such as the optoelectronic properties and the adsorption energies in the TiO2 clusters, were calculated with counterpoise correction and discussed.

Solution‐Processable Pure‐Red Multiple Resonance‐induced Thermally Activated Delayed Fluorescence Emitter for Organic Light‐Emitting Diode with External Quantum Efficiency over 20 %

AbstractDeveloping solution‐processable red organic light‐emitting diodes (OLEDs) with high color purity and efficiency based on multiple resonance thermally activated delayed fluorescence (MR‐TADF) is a formidable challenge. Herein, by introducing auxiliary electron donor and acceptor moieties into the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributed positions of multiple resonance skeleton simultaneously, an effective strategy to obtain red MR‐TADF emitters was represented. The proof‐of‐the‐concept molecule BN‐R exhibits a narrowband pure‐red emission at 624 nm, with a high luminous efficiency of 94 % and a narrow bandwidth of 46 nm. Notably, the fabricated solution‐processable pure‐red OLED based on BN‐R exhibits a state‐of‐the‐art external quantum efficiency over 20 % with the Commission Internationale de I’Éclairage coordinates of (0.663, 0.337) and a long operational lifetime (LT50) of 1088 hours at an initial luminance of 1000 cd m−2.

Solution-Processable Pure-Red Multiple Resonance-induced Thermally Activated Delayed Fluorescence Emitter for Organic Light-Emitting Diode with External Quantum Efficiency over 20.

Developing solution-processable red organic light-emitting diodes (OLEDs) with high color purity and efficiency based on multiple resonance thermally activated delayed fluorescence (MR-TADF) is a formidable challenge. Herein, by introducing auxiliary electron donor and acceptor moieties into the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributed positions of multiple resonance skeleton simultaneously, an effective strategy to obtain red MR-TADF emitters was represented. The proof-of-the-concept molecule BN-R exhibits a narrowband pure-red emission at 624 nm, with a high luminous efficiency of 94% and a narrow bandwidth of 46 nm. Notably, the fabricated solution-processable pure-red OLED based on BN-R exhibits a state-of-the-art external quantum efficiency over 20% with the Commission Internationale de I'Éclairage coordinates of (0.663, 0.337) and a long operational lifetime (LT50) of 1088 hours at an initial luminance of 1,000 cd m-2.

Studying of 2,2′-Bipyrimidine Based Dyes Properties as Photo-Sensitizer for Dye Sensitized Solar Cells (DSSCs)

In this investigation, five novel π-new organic donor-π-acceptor dyes (D-π-A) based on 2,2′-bipyrimidines were used. For optimization and DFT research, respectively, the 6-311+G(d,p) basis set and B3LYP density functional theory were applied. In all the systems, diphenyl amine moiety acts as the electron-donor component, whereas the nitro/cyano moiety as electron acceptor (anchoring) group. In the conjugated spacer, a methyl/ethyl substituent was used to examine the impact of the auxiliary donor group. The computed HOMO-LUMO gap and the spectral data matched well. The oscillator strength (f), electron injection free energy (ΔGinject) and light-harvesting efficiency (LHE) were also computed and explained. The calculated values for the examined dye-sensitizers open-circuit photo voltage (Voc) and electron coupling constant (VRP) were also included in this research. This study demonstrates that every synthetic dye has promising potential as a dye sensitized solar cells (DSSCs) sensitizer.

D-D-π-A-π-A-based quinoxaline dyes incorporating phenothiazine, phenoxazine and carbazole as electron donors: Synthesis, photophysical, electrochemical, and computational investigation

Three novel D-D-π-A-π-A types of metal-free organic dyes, QX-D1, QX-D2, and QX-D3, were designed and synthesized in excellent yields (94–99 %). An auxiliary acceptor of 2,3-diphenylquinoxaline was incorporated between two units of thiophene as π-spacers so that one ring is connected with cyanoacrylic acid as an anchoring electron acceptor, and the other one lies between the quinoxaline moiety and an electron donor to build the π-A-π-A part.The other D-D part of the dye skeleton was made using donors-based phenothiazine (PTZ), phenoxazine (POZ), and carbazole (CZ) containing a tolyl moiety as an auxiliary donor. For this purpose, an efficient multistep synthetic approach for the synthesis of the dyes was investigated. The chemical structures of all compounds were confirmed by spectral data (FTIR, 1H NMR, 13C NMR, and HRMS). The QX-D1, QX-D2, and QX-D3 dyes showed ICT bands in THF solution at 511, 542, and 526 nm, respectively and high molar absorptivity of 23434, 29825, and 23214 M−1 cm−1, respectively. Among the donor, QX-D2-based POZ revealed bathochromic and hyperchromic shifts in the absorption due to the influence of the oxygen atom in POZ compared with the sulfur atom and non in PTZ and CZ, respectively. The cyclic voltammetry data revealed that the HOMO and LUMO energy levels forQX-D1,QX-D2, andQX-D3dyes were found to be (−5.07, −2.86 eV), (−4.90, −2.72 eV), and (−5.13, −3.04 eV), respectively. Furthermore, the density functional theory (DFT) and time-dependent TD-DFT at the B3LYP/6-31G(d) level were investigated to shed light on the bridged effect on geometric and TD-BH and H/6-31G(d) for optoelectronic properties. The binding energies of the complex dye@TiO2 cluster have also been explored. A good agreement between theoretical and experimental data was obtained. Thus, the dyes successfully achieved the desired outcomes, qualifying them for later use in photovoltaic applications such as sensitizers in dye-sensitized solar cells (DSSCs).