Triphenylamine Dyes Research Articles

Unveiling the potential of TPA-based molecules to tune the optoelectronic properties and enhance the efficiency of dye-sensitized solar cells.

The world's energy and environmental requirements are changing due to rapid population growth and industrial growth, and solar cells can be used to meet these demands. Dye-sensitized solar cells (DSSCs) are solar cells in which energy conversion occurs via a process similar to photosynthesis in plants. DSSC development is still in its infancy. DSSCs can operate under cloudy conditions and indirect sunlight and have attracted considerable attention due to their low cost and high efficiency. We designed two metal-free TPA-based dyes (Dye2 and Dye3) based on the reference dye Mg207 (Dye1) by increasing the donor strength of the molecule, as such dyes have shown enhanced efficiency in DSSCs. Moreover, the triphenylamine (TPA) moiety has been demonstrated to be a good donor that prevents charge recombination. Intramolecular charge transfer (ICT) from the donor to acceptor moiety was found in the sensitizers, and electrons were promoted to the conduction band (CB) of the TiO2 semiconductor. The negative binding energy of the dye@TiO2 clusters indicated that dye adsorption on the semiconductor surface was stable. The double donor increased the electron injection and electronic coupling constants in Dye2 and Dye3, indicating that these newly designed dyes have superior charge injection capacity. Accordingly, the efficiencies of DSSCs with Dye2 and Dye3 were 9.77% and 9.62%, respectively, and substitution with the TPA unit at the -R1 and -R2 positions in Dye1 resulted in better power conversion compared to the parent compound (9.09%). Increased donor strength improved photovoltaic performance by increasing current density and light-harvesting efficiency. This is a good molecular design approach for preparing targeted donor- -acceptor (D- -A) organic dyes with high DSSC efficiency. To predict the charge transport and optoelectronic characteristics of the TPA dyes, quantum chemical calculations were carried out using Gaussian16. The ground-state (S0) optimized geometries of the sensitizers were computed by utilizing DFT at the B3LYP/6-31G** level. The absorption spectra ( max) were computed by employing TD-DFT with various functionals (B3LYP, PBE1PBE, CAM-B3LYP, and BHandHLYP) in the gas and solvent (DCM) phases. Among the studied functionals, BHandHLYP was found to be best at successfully reproducing the experimental data. Thus, the absorption spectra of the newly designed dyes and dye@TiO2 were calculated at the BHandHLYP/6-31G** level. The dye@TiO2 cluster optimizations were carried out at the B3LYP/6-31G**(LANL2DZ) level.

Theoretical exploration of copper based electrolytes for third generation dye sensitized solar cells

Dye-sensitized solar cells (DSSCs) present a promising avenue for addressing the escalating need for clean energy solutions. These innovative cells offer a sustainable approach to meet the rising demands for environmentally friendly power sources. An assessment was conducted on a copper complex containing a hexadentate ligand, serving as a redox shuttle, alongside triphenylamine-based organic dyes in the construction of DSSC. This study thoroughly investigates the electronic structures, FMO, MEP surfaces, and photophysical properties of copper redox shuttle and triphenylamine dyes employing DFT and TDDFT calculations. The copper system, [Cu(bpyPY4)]2+/+, analyzed in this study, is anchored by the hexadentate polypyridyl ligand bpyPY4 (6,6′-bis(1,1-di(pyridine-2-yl)ethyl)-2,2′-bipyridine), scrutinized as a redox shuttle (RS). The assessed redox potential for [Cu(bpyPY4)]2+/+ is −4.67 eV. This indicates that the dye can effectively undergo regeneration by transferring electrons from the reduced form of the redox shuttle to the oxidized form of the dye. The photovoltaic efficiency has been analyzed with regard to various factors, including the energy gap between the HOMO and LUMO, the excited-state oxidation potential (Edye*), electron injection ability (∆Ginj), electron regeneration (∆Greg), light harvesting efficiency, short-circuit current density (JSC) and the open-circuit voltage (Voc). This study sheds light on present-day developments and forthcoming prospects in utilizing 3d transition metal-based redox shuttles, presenting them as compelling candidates for integration with organic dyes in Dye-Sensitized Solar Cells (DSSCs). This integration holds promise for more efficient solar spectrum absorption and enhanced performance of solar devices.

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%).

Ultrafast Photophysics of Regioisomeric Triphenylamine Dyes having Dipolar D-π-A-A and Octupolar D-(π-A-A)3 Character with a Benzothiazole Unit in Matched or Mismatched Orientation.

Benzothiazole is among prominent electron-withdrawing heteroarene moieties used in a variety of π-conjugated molecules. Its relative orientation with respect to the principal dipole vector(s) of chromophores derived thereof is crucial, affecting photophysical and nonlinear optical properties. Here we compare the photophysics and ultrafast dynamics of dipolar and octupolar molecules comprising a triphenylamine electron-donating core, ethynylene π-conjugated linker(s) and benzothiazole acceptor(s) having the matched or mismatched orientation (with respect to the direction of intramolecular charge transfer), while a carbaldehyde group is attached as an auxiliary acceptor. Among chromophores without the auxiliary acceptor, stronger fluorescence solvatochromism and faster excited state dynamics are exhibited for the derivatives with the mismatched geometry. On the contrary, introduction of the auxiliary acceptor to the benzothiazole unit enhances the intramolecular charge transfer ICT (featuring ultrafast dynamics of the excited state) for the matched geometry. The data confirm the crucial role of the relative orientation of asymmetric heteroaromatic unit (regioisomeric effect) in dipolar as well as in multipolar molecules in tuning linear and nonlinear optical properties as well as excited state dynamics.

The impact of aromatic π-spacers and internal acceptors in triphenylamine dyes for DSSCs: A DFT approach

In present work, the influence of internal acceptors and π-spacers on optoelectronic properties for dye-sensitized solar cells (DSSCs) is investigated. The dyes consist of various internal acceptors (A), a triphenylamine donor and π-spacers combined with cyanoacrylic acid acceptor. Density functional theory (DFT) was employed to inspect the dye geometries, charge transport characteristics and electronic excitations. The frontier molecular orbitals (FMOs), highest occupied molecular orbital, lowest unoccupied molecular orbital and HOMO-LUMO energy gap are assisted in the determination of suitable energy levels for electron transfer, electron injection and regeneration of dye. The required photovoltaic parameters like JSC, ΔGreg, ΔGinj, LHE and other associated parameters are presented. The results demonstrate that altering the π-bridge and adding an internal acceptor to the D-π-A scaffold changes the photovoltaic properties and absorption energies. Therefore, the key objective of the current effort is to launch a theoretical groundwork for suitable operational alterations and scheme in creating successful DSSCs.

Novel pyridoquinazolindone-containing triphenylamine dyes for dye-sensitized solar cells

Four novel “A-D-π-A” pyridoquinazolinone-containing triphenylamine dyes were synthesized for dye-sensitized solar cell (DSSCs), which consist of triphenylamine as the electron donor, thiophene or CC bond as π-bridge, cyanoacrylic acid as the electron acceptor and pyridoquinazolinone as the auxiliary acceptor. Their photophysical, electrochemical properties and photovoltaic performance were investigated. Moreover, density functional theory (DFT) was performed for theoretical calculations. The results show that the incorporation of additional pyridoquinazolinone unit enables dyes with larger charge recombination resistance than the dyes with single pyridoquinazolinone unit, which benefits the increase of Voc. Besides, the introduction of thiophene bridge can broaden and red-shift the absorption region, which endows the dyes with better light-harvesting ability and subsequently brings about superior IPCE and Jsc. Therefore, dye with double pyridoquinazolinone units and thiophene bridge exhibits the best photoelectric conversion efficiency 5.19 % (Jsc = 11.71 mAcm−2, Voc = 0.67 V, ff = 0.70).

Experimental and computational study of triphenylamine dyes for photovoltaic cell applications

We investigate a new family of the triphenylamine dyes by the help of quantum physics computations relaying on density functional theory (DFT) including time dependent-density functional theory (TD-DFT) calculations. We examine the distributions of molecular orbitals, the light collection efficiency, the absorption properties, the oscillator forces, the electronic excitation energy, and the injection driving forces. Among others, we reveal that the organic dyes involve a narrow band gap and good optical behaviors. Moreover, we approach the photovoltaic features of such novel materials. We find that they exhibit the capacity to inject the electrons into the conduction band. We expect that the obtained results could support the applications of such materials in solar energy productions.

Developing efficient dye-sensitized solar cells by inclusion of ferrocene and benzene π-bridges into molecular structures of triphenylamine dyes

Two triphenylamine (TPA)-based D─π─A sensitizers have been introduced with benzene (B) and ferrocene (Fc) π-bridges which were named as TPA-diazo-B and TPA-diazo-Fc for comparing their ability to find better insight about relation between dye structure and power conversion efficiency (PCE) of dye sensitized solar cells (DSSCs). The optical, electrochemical, interfacial and photovoltaic (PV) properties of these dyes revealed that replacing the B π-bridge with Fc not only provides bathochromic shift in absorption wavelength, but also tunes the band gap (Eg) to the smaller value. In consistent with these observations, PV characteristics of TPA-diazo-Fc sensitized devices (JSC = 1 4.60 mA cm−2, VOC = 652.26 mV, FF = 57% and PCE = 5.42%) were better than DSSCs that used the TPA-diazo-B (JSC = 12.91 mA cm−2, VOC = 619.15 mV, FF = 55% and PCE = 4.46%) for sensitization. Inclusion of a Fc π-bridge improves the intramolecular charge transfer (ICT) from donor (D) to acceptor (A) in dye structure. The main reason for such great ICT is presence of quantum interference effects (QIEs) in Fc π-bridge that facilitates the single molecule conductance of TPA-diazo-Fc dye in comparison to TPA-diazo-B. This study revealed a new horizon in molecular engineering of dyes for developing DSSCs with better performance.

Synthesis and solar cell power conversion efficiency improvement of π-extended triphenylamine dyes for indoor light-based applications

Synthesis and solar cell power conversion efficiency improvement of π-extended triphenylamine dyes for indoor light-based applications

Charge recombination suppression in dye-sensitized solar cells by tuning the dielectric constant of triphenylamine dyes with altering π-bridges from naphthalene to anthracene units.

Charge recombination reactions (CRRs) are responsible for the major loss of power conversion efficiency (PCE) in dye-sensitized solar cells (DSSCs). This study tracks the impact of the dielectric constant (ε') of two D-π-A types of triphenylamine-based organic dyes (TpAzo 1 and TpAzo 2) with naphthalene and anthracene π-bridges on CRRs, respectively, and these dyes are sandwiched as dielectric layers of capacitors between Al electrodes via rf-sputtering deposition. The structure and thickness of components of capacitors were considered by applying field emission scanning electron microscopy (FESEM), and ε', ε'', tan δ, ac conductivity (σac) and electric modulus (M*) of capacitors were analyzed by LCRmetry at different frequencies (f: 102-104 Hz) and temperatures (T: 299-390 K). Cyclic voltammetry (CV) and UV-visible spectroscopy analysis of dyes were performed for revealing the optical profiles, highest occupied molecular orbitals (HOMO), lowest unoccupied molecular orbitals (LUMO), and band gap (Eg); the results were found to be highly consistent with density functional theory (DFT) quantum calculation outputs. The f- and T-dependent relationships were detected for ε', ε'', tan δ and σac, which experienced an upward trend and a downward trend with the increase in T and the decrease in f, respectively. The results indicated higher ε', ε'' M' and M'' values for TpAzo 2 than those of TpAzo 1, which from the molecular point of the view could be related to the more extending π-conjugated structure of anthracene in comparison to naphthalene π-bridges that not only provided appropriate dipole moments and exciton binding energy, but also facilitated powerful intramolecular charge transfer (ICT). Therefore, this study proposes ε', ε'', M' and M'' as novel physiochemical characters in dye design, which have been neglected so far and can open a new synthesis paradigm for developing more efficient organic sensitizers for DSSCs.

Design and Synthesis of D‐π‐A form of p‐Nitrophenylacrylonitrile Substituted Triphenylamine Chromophores; Photophysical, Electrochemical Properties, DFT and Thermal Studies

AbstractThis paper reports a novel Donor‐π‐Acceptor type of π‐conjugated triphenylamine (TPA) dyes bearing a 4‐nitrophenyl acrylonitrile units (abbreviated as TPA‐4(a–e) which were synthesized by Knoevenagel condensation followed by palladium catalyzed Suzuki‐Miyaura cross coupling reaction with good yield. These dyes contain TPA as electron donor (D) and 4‐nitrophenyl acrylonitrile as electron acceptor (A) and probes were confirmed by standard spectroscopic techniques viz.,1H, 13C NMR, FT‐IR, GC‐MS and ESI‐MS. Herein, for the D‐π‐A push‐pull structure, TPA and 4‐nitrophenyl acrylonitrile are connected by vinylene bond as the π‐bridge. Optical/Solvatochromic properties were studied in detail by UV‐Vis absorption and fluorescence spectroscopy. The intramolecular charge transfer properties were studied using DFT model with the CAM‐B3LYP function and solvatochromism by experimental method. The synthesized materials have shown moderate quantum yields. Optical bandgap values range from 2.33 to 2.39 eV and these derivatives exhibit well judged thermal stability and their 5 % weight loss temperature are in the range 178–220 °C. Cyclic voltametery study of the title compounds indicated that values ranging from 1.05–1.25 eV. Quantum yields (Φ) of the probes are experimentally measured in the 1, 4‐dioxane and the Stokes shifts are observed to be in the range of 4882–5545 cm−1. The results displayed that these novel (D−A−D) chromophores could play an important role in the organic optoelectronics.

A soft x-ray probe of a titania photoelectrode sensitized with a triphenylamine dye.

We present a thorough soft x-ray photoelectron spectroscopy (XPS) study of a mesoporous titanium dioxide electrode sensitized with the dye 4-(diphenylamino)phenylcyanoacrylic acid, referred to as "L0." Supported by calculations, the suite of XPS, x-ray absorption spectroscopy, and resonant photoelectron spectroscopy allows us to examine bonding interactions between the dye and the surface and the frontier electronic structure at the molecule-oxide interface. While placing these measurements in the context of existing literature, this paper is intended as a useful reference for further studies of more complex triphenylamine based sensitizers.

Triphenylamine dyes bearing 4-phenyl-2-(thiophen-2-yl)thiazole bridge for dye sensitized solar cells

Three triphenylamine dyes were synthesized with 4-phenyl-2-(thiophen-2-yl)thiazole as π-bridge and cyanoacrylic acid as the acceptor. The molecular structures of three compounds differ in the substituent on the triphenylamine donor. With the incorporation of the electron-withdrawing aldehyde or cyanoacrylic acid unit on the triphenylamine donor, the intramolecular charge transfer was weakened, which was characterized by the blueshifted absorption and the decreased molar extinction coefficient. The presence of aldehyde or cyanoacrylic acid unit raises the loading amount of dye on TiO2, however, increase the aggregation rate, bringing down VOC. Therefore, dye without substituent on the triphenylamine donor outperformed the other two dyes due to superior JSC and VOC, affording a 4.89 % cell efficiency.

Propellar shaped triple bond rigidified D-A-π-A triphenylamine dye as back electron interceptor in iodine and cobalt electrolyte DSSCs under full sun and indoor light

In the present manuscript, we report the synthesis and characterization of a new molecularly engineered triple bond rigidified D-A-π-A propeller shaped triphenylamine dye having benzothiadiazole as auxiliary acceptor (TPAA8). We compared the behavior of TPAA8 with the parent dye TPAA1 in D-π-A architecture without auxiliary acceptor, which was reported previously from our group (Vinayak et al., 2016). TPAA8 was found to be efficient in harvesting light and was having a favourable energetics suitable to realize forward electron transfer process in fabricated devices. TPAA8 with the introduction of auxiliary benzothiadiazole acceptor proved to be a promising candidate in preventing recombination with conventional iodine and alternate cobalt based redox electrolytes which was studied in detail employing various optical and electrical perturbation techniques. With alternate cobalt electrolyte ([Co(bpy)3]2+/3+) TPAA8 delivered an improved performance of 6.40 ± 0.05%, which is an improvement of 124% in power conversion efficiency compared to the parent TPAA1 sensitizer devoid of auxiliary acceptor having an efficiency of 2.85%. TPAA8 also proved to be an efficient candidate for indoor light harvesting delivering a power conversion efficiency of 11.03 ± 1.7% employing [Co(bpy)3]2+/3+ redox mediator under 1000 lux warm white LED illumination.

Size controlled silver nanoparticles on β-cyclodextrin/graphitic carbon nitride: an excellent nanohybrid material for SERS and catalytic applications.

A nanohybrid (NH), having high dispersion of silver nanoparticles (AgNPs) on β-cyclodextrin (β-CD)/graphitic carbon nitride (g-CN), designated as AgNPs/β-CD/g-CN-NH, was synthesized and characterized. It was exploited for a couple of environmental remediation applications like SERS sensing and catalytic reduction of specific organic pollutants in water. It showed excellent SERS activity as a Raman probe for the detection of malachite green (MG). Its enhancement factor (EF) and detection limit for MG were equal to 7.26 × 106 and 1 × 10-9 M, respectively. The relative standard deviation (RSD) was equal to 3.8% which indicates high homogeneity of AgNP dispersion and signal reproducibility of the SERS substrate. The NH displayed high catalytic activity for the reduction of eosin yellow (EY) in the presence of NaBH4 with the rate constant (k) of 0.1142 min-1. A comparison of the present NH with other reported materials reveals better SERS and catalytic activities of the former than those of the latter. The SERS activity of the NH was also examined for sensing of other triphenylamine dyes like methyl violet (MV), and it was successful. The same NH also exhibited high catalytic activity towards the reduction of Congo red (CR). The results of both studies clarify that the NH is an excellent SERS substrate and efficient catalyst for the detection of organic environmental pollutants having structures similar to MG and their degradation. This is due to the distribution of the controlled size of AgNPs on g-CN promoted by β-CD. Therefore, we focus our attention on future environmental applications of the nanohybrid as a very cheap SERS substrate and a very active catalyst.

The effect of benzoxazole unit on the properties of cyclic thiourea functionalized triphenylamine dye sensitizers

Two D-π-A-A sensitizers (AZ6-B20 and AZ6-B21) were synthesized by inserting the benzoxazole group as an auxiliary acceptor between the π-linker and the acceptor. And a D-A-π-A sensitizer (AZ6-B19) was also synthesized in our previous works by the insertion of the benzoxazole between the donor and the π-linker. The effects of benzoxazole groups on the properties at different sites of dye sensitizers were distinguishing. Their light harvest abilities were investigated by UV–vis spectra both in the solution and on the films. The results show that the absorption bands of UV–vis spectra are quite different from D-A-π-A and D-π-A-A dyes. The much more intensive molar extinction coefficients (53807 M−1cm−1 and 52555 M−1cm−1) were observed at around 575 nm for D-π-A-A dyes. The photovoltaic properties of DSSCs were also evaluated by J-V curves and IPCE measurements. The results confirmed that D-π-A-A dyes delivered high photovoltaic efficiency (AZ6-B20: 7.48%, AZ6-B21: 8.67%) compared with that of D-A-π-A dye (AZ6-B19: 3.27%). The details on the relation of the structures/properties were discussed by the optical physical absorption, electrical chemical measurements and DFT calculations.

Triphenylamine dyes bearing 5-phenyl-2-(arylthiophen-2-yl)thiazole bridge for dye sensitized solar cells

Three triphenylamine dyes were synthesized with 5-phenyl-2-(arylthiophen-2-yl)thiazole as π bridge and cyanoacrylic acid as the acceptor. Three dyes differ in the aryl ring binding with the acceptor in the π bridge, which leads to different photophysical properties, molecular planarity, energy level and accordingly the photoelectric conversion efficiency. The insertion of furan and thiophene units in π bridge attain broader absorption spectra and better molecular coplanarity, contributing to the distinct improvement of JSC and hence the photovoltaic performance. On the other hand, the presence of benzene unit raises the LUMO level and increases the drive force for the electron injection into TiO2, which enhance VOC. Among three dyes, dye bearing two thiophene units sensitized DSSC achieves a cell efficiency 6.90% due to better JSC (14.09 mA cm2) and VOC (0.73 V).

Theoretical Investigation on Photophysical Properties of Triphenylamine and Coumarin Dyes.

Organic molecules with donor and acceptor configures are widely used in optoelectronic materials. Triphenylamine dyes (TPCTh and TPCRh) are investigated via density functional theory (DFT) and time-dependent DFT. Some microscopic parameters related to light absorption and photoelectric formation are calculated to interpret the experimental performance in dye-sensitized solar cells (DSSCS). Considering that coumarin derivatives (Dye 10 and Dye 11) have good donor and acceptor structures, they also have a COOH group used as an anchoring group to connect with semiconductors. Thus, the two dyes’ photophysical and photoelectric properties are analyzed to estimate the performance and application in DSSCs.

Effects of heteroatoms in π-conjugated linkers on the optical and electronic properties of modified triphenylamine based dyes: towards DSSCs' applications.

Optoelectronic properties of triphenylamine dyes arising from the embedded five-membered π-linkers C4H4X (X = O, NH, S, Se, Te) and varying anchoring groups, cyanoacrylic acid and hydantoin, in D-π-π-A model are examined. The reported properties for both, isolated dyes and dye@TiO2 complexes, are realized through density functional theory (DFT) and time-dependent DFT. The study reveals that chalcogen doping (X = S, Se, Te) enhances absorption and fluorescent emission spectra in the visible and NIR regions. The adsorption of the dyes on the TiO2 cluster has been simulated. Alteration of the UV-Vis spectra and electron density redistribution for the complexes from individual dyes are examined and analyzed. The binding energies relate to the nature of the heteroatoms X; the complexes dye@TiO2 with heavier heteroatoms Se and Te demonstrate stronger binding. Graphical abstract.

Double Linker Triphenylamine Dyes for Dye-Sensitized Solar Cells

Most organic dyes synthesized for dye-sensitized solar cells (DSC) use a single linker group to bind to the metal oxide photo-anode. Here we describe the synthesis and testing of two new triphenylamine dyes containing either two carboxylic acids 5-[2-(4-diphenylamino-phenyl)-vinyl]-isophthalic acid (10) or two cyanoacrylic acids (2Z, 2′Z)-3, 3′-(5-((E)-4-(diphenylamino) styryl)-1, 3-phenylene) bis (2-cyanoacrylic acid) (8) as linker groups. Full characterization data are reported for these dyes and their synthetic intermediates. DSC devices have been prepared from these new dyes either by passive or fast dyeing and the dyes have also been tested in co-sensitized DSC devices leading to a PCE (η = 5.4%) for the double cyanoacrylate linker dye (8) co-sensitized with D149. The dye:TiO2 surface interactions and dye excitations are interpreted using three modelling methods: density functional theory (at 0 K); molecular dynamics (at 298 K); time dependent density functional theory. The modelling results show the preferred orientation of both dyes on an anatase (1 0 1) TiO2 surface to be horizontal, and both the simulated and experimental absorption spectra of the dye molecules indicate a red shifted band for (8) compared to (10). This is in line with broader light harvesting and Jsc for (8) compared to (10).