Auxiliary Donor Research Articles

Enhanced photovoltaic performances of dye-sensitized solar cells sensitized with D-D-π-A phenothiazine-based dyes

Two new D-D-π-A phenothiazine-based metal free organic dyes (WY5, WY6) were designed, synthesized, and applied in dye-sensitized solar cells (DSSCs) by introducing of benzil-based auxiliary electron donors into simple D-π-A phenothiazine dye to improve the related photovoltaic performances. In the WY6-based solar cell, 4,4′-dimethoxybenzil acts as electron donor was used to improve the electron donating ability. So, the WY6-based solar cell finally obtains a better photovoltaic performance than that of WY5-based one. Furthermore, with the addition of benzil-based auxiliary donor, the absorption properties turn better, which directly results in the enhanced short-circuit photocurrent density (from 8.78 (T0) to 10.58 (WY5) and 11.50mAcm−2 (WY6)) and thus the enhanced power conversion efficiency (from 4.24 (T0) to 4.78 (WY5) and 5.52% (WY6)). In a word, the addition of benzil-based auxiliary electron donors effectively improved the performances of DSSCs.

Extremely Robust and Patternable Electrodes for Copy-Paper-Based Electronics

We propose a fabrication process for extremely robust and easily patternable silver nanowire (AgNW) electrodes on paper. Using an auxiliary donor layer and a simple laminating process, AgNWs can be easily transferred to copy paper as well as various other substrates using a dry process. Intercalating a polymeric binder between the AgNWs and the substrate through a simple printing technique enhances adhesion, not only guaranteeing high foldability of the electrodes, but also facilitating selective patterning of the AgNWs. Using the proposed process, extremely crease-tolerant electronics based on copy paper can be fabricated, such as a printed circuit board for a 7-segment display, portable heater, and capacitive touch sensor, demonstrating the applicability of the AgNWs-based electrodes to paper electronics.

Different Effect of the Additional Electron-Withdrawing Cyano Group in Different Conjugation Bridge: The Adjusted Molecular Energy Levels and Largely Improved Photovoltaic Performance.

Four organic sensitizers (LI-68-LI-71) bearing various conjugated bridges were designed and synthesized, in which the only difference between LI-68 and LI-69 (or LI-70 and LI-71) was the absence/presence of the CN group as the auxiliary electron acceptor. Interestingly, compared to the reference dye of LI-68, LI-69 bearing the additional CN group exhibited the bad performance with the decreased Jsc and Voc values. However, once one thiophene moiety near the anchor group was replaced by pyrrole with the electron-rich property, the resultant LI-71 exhibited a photoelectric conversion efficiency increase by about 3 folds from 2.75% (LI-69) to 7.95% (LI-71), displaying the synergistic effect of the two moieties (CN and pyrrole). Computational analysis disclosed that pyrrole as the auxiliary electron donor (D') in the conjugated bridge can compensate for the lower negative charge in the electron acceptor, which was caused by the CN group as the electron trap, leading to the more efficient electron injection and better photovoltaic performance.

Triphenylamine-based redox-active aramids with 1-piperidinyl substituent as an auxiliary donor: Enhanced electrochemical stability and electrochromic performance

A new triphenylamine-based diamine monomer 4,4′-diamino-4″-(1-piperidinyl)triphenylamine was synthesized and polymerized with various aromatic dicarboxylic acids via the phosphorylation polyamidation technique leading to a series of redox-active aromatic polyamides (aramids). All the aramids exhibit good solubility in many organic solvents and can be solution-cast into flexible and strong films with high thermal stability. Cyclic voltammograms of the polymer films on the indium-tin oxide (ITO)-coated glass substrate exhibit a pair of well-defined and reversible oxidation waves with very low onset potentials of 0.27–0.35V (vs. Ag/AgCl) in acetonitrile solution, with a strong color change from colorless neutral form to green and deep blue oxidized forms in the range of 0.75–1.20V. The optical transmittance change (Δ%T) at 636nm between the neutral state and the fully oxidized state is up to 83%.

Theoretical Investigation of Novel Tetrathiafulvalene- Triphenylamine Sensitizers

Two novel sensitizers with D-D-pi-A (YD2) and 2D-D-pi-A (YD3) structures were designed by introducing different numbers of tetrathiafulvalene (TTF) unit as the auxiliary electron donor based on the simple D-pi-A triphenylamine sensitizer (YD1) to enhance the electron donating ability. The geometries, electronic structures, and optical properties of YD1-3 before and after binding to TiO2 clusters were investigated. Owing to introduction of TTF unit, YD2 and YD3 show larger steric hindrance and a narrower band gap than YD1. Moreover, the estimated light-harvesting efficiency (LHE), injection driving force (Delta G(inject)) values, and density of states (DOS) calculations indicate that YD2 and YD3 should show higher short-circuit photocurrent density (J(sc)) and open-circuit photovoltage (V-oc) than YD1 with the presence of TTF unit. All of the results indicate that TTF unit can be used as an auxiliary electron donor in organic sensitizers to improve their photovoltaic properties.

Role of auxiliary donors in tuning the selectivity of C-H activation in arylazonaphthalenes by palladium(II) : Isolation and photoisomerization of isomeric cyclopalladates

Role of auxiliary donors in tuning the selectivity of C-H activation in arylazonaphthalenes by palladium(II) : Isolation and photoisomerization of isomeric cyclopalladates

Palladium complexes of C/Se and N/E (E = Se, Te) ligands, 2-(3,5-dimethylpyrazol-1-yl)phenyl substituted chalcogeno-ethers: Functional group effect on structure and catalytic activity

Several tri-dentate ionic monochloro-palladium complexes of the type, [PdCl(NˆEˆN′)][OTf] (3a-c, 3′a, 3′c) and [PdCl(CˆSeˆN′)][OTf] (3d) (where, E = Se, Te; N′ = 2-(3,5-dimethylpyrazol-1-yl)phenyl; N = ethylamine/N, N-dimethylethylamine/picolyl and C = 1-methyl-3-ethyl-2,3-dihydro-1H-imidazol carbene, respectively) were isolated from corresponding dichloro complexes (2a–d, 2′a, 2′c) prepared by reacting PdCl2 with equimolar amount of seleno-ether ligands. Some of the representative ionic complexes were unambiguously analyzed by single crystal X-ray diffraction method, and employed for Suzuki–Miyaura carbon–carbon coupling reactions. The effect of subtle changes in ligands, such as variation in auxiliary donor group or chalcogen atom, on crystal structure and catalytic efficiency has been investigated. For the above mentioned studies, auxiliary donor groups of different donor strength such as amines/pyridyl (N-donor) and imidazole based carbene (C-donor) were introduced in seleno-ether ligands.

Synthesis, crystal structures, and two-photon absorption of a series of cyanoacetic acid triphenylamine derivatives

A specific series of chromophores (CN1, CN2, CN3, and CN4) have been synthesized, in which contained a triphenylamine moiety as the electron donor (D), a cyanoacetic acid moiety as the electron acceptor (A), vinylene or phenylethyne as the π-bridge, and ethyoxyl groups as auxiliary electron donor (D′) to construct the D-π-A or D′–D-π-A molecular configuration. Photophysical properties of them were systematically investigated. These results show that the chromophores display a solvatochromism (blue shift) and large Stokes shifts for their absorption bands with increasing polarity of the solvent. Furthermore, the chromophore CN4 shows the strongest intensity of two-photon excited fluorescence and largest two-photon absorption cross section (2783 GM) in the near infrared region. Finally, the connections between the structures and properties are systematically investigated relying on the information from linear and nonlinear optical properties, crytsal structures and quantum chemical calculation.

Benefits of the use of auxiliary donors in the design and preparation of NLO chromophores

Organic electro-optic (EO) materials have been widely studied and used in microwave photonic devices, due to their advantages in half-wave voltage, bandwidth, low cost and ease of integration. Nonlinear optical (NLO) chromophores, as the core of organic EO materials, can directly decide the characters of organic EO materials, including large EO activity, long term stability, solubility and optical loss. Auxiliary donors have attracted great attentions in NLO chromophores for their strong electron donating ability and significant isolation effect. This feature article describes the application of auxiliary donor in NLO chromophores, including the EO activities, optical characters, stability, crystal structures and machinability.

Auxiliary donor for tetrahydroquinoline-containing nonlinear optical chromophores: enhanced electro-optical activity and thermal stability

New chromophores L1 and L2 containing a novel tetrahydroquinoline-based donor were synthesized, resulting in enhanced electro-optic activity.

Enhancement of nonlinear optical (NLO) properties of indigo through modification of auxiliary donor, donor and acceptor

In this study, indigo based dyes with high non-linear optical response have been investigated. Density functional theory (DFT) was used to study non-linear optical properties of indigo and newly designed dyes (IM-Dye-0, IM-Dye-1, IM-Dye-2 and IM-Dye-3). The time dependant density functional theory (TDDFT) was used to calculate the excitation energies. The HOMO–LUMO energy gaps of newly designed dyes were smaller as compare with indigo dye. Absorption maxima of newly designed dyes strongly red shifted as compare with indigo dye. High non-linear optical (NLO) response of newly designed dyes revealed that these materials would be excellent for NLO applications. This theoretical approach of designing will pave the way for experimentalists to synthesize high response NLO compound.

Organic dyes containing a hydrazone moiety as auxiliary donor for solid-state DSSC applications

D-D-π-A architecture metal-free organic dyes, containing a hydrazone moiety as an auxiliary donor were designed and synthesized for solid-state dye-sensitized solar cells. The sensitizer series was designed to develop a structure-property relationship. These dyes were obtained from the relatively cheap starting materials, without the use of expensive catalysts, rigorously anhydrous or oxygen-free conditions. The highest solid-state device conversion efficiency 3.9% (JSC = −7.9 mA cm−2, VOC = 760 mV) and fill factor 0.65 under 100 mWcm−2 (AM 1.5G) solar irradiation were achieved with the dye D3 containing a methoxy group attached to the triphenylamine donor unit employed between the hydrazone moiety and rhodanine acceptor of the sensitizer.

Haplo-Cord Transplantation Using CD34+ Cells from a Third-Party Donor to Speed Engraftment in High-Risk Patients with Hematologic Disorders

Among the strategies to optimize engraftment of cord blood (CB) stem cell transplantation (SCT), single CB with the coinfusion of CD34+ stem cells from an HLA-mismatched auxiliary donor (haplo-cord) provides a valid alternative for adult patients without a suitable donor. A total of 132 high-risk adult patients with hematological malignancies from 3 Spanish institutions underwent myeloablative haplo-cord SCT. The median age was 37 years and median weight was 70 kg; 37% had active disease. The median number of postprocessing CB total nucleated and CD34+ cells was 2.4 × 107/kg (interquartile range [IQR], 1.8 to 2.9) and 1.4 × 105/kg (IQR, .9 to 2), respectively. Neutrophil engraftment occurred in a median of 11.5 days (IQR, 10.5 to 16.5) and platelet engraftment at 36 days (IQR, 25.5 to 77). Graft failure was 2% overall and only 9% for CB. Cumulative incidence of acute graft-versus-host disease (GHVD) grades II to IV was 21% and cumulative incidence of chronic GVHD was 21%. Median follow-up was 60 months (range, 3.5 to 163). Overall survival was 43.5%, event-free survival was 38.3%, nonrelapse mortality was 35%, and relapse was 20% at 5 years. Myeloablative haplo-cord SCT results in fast engraftment of neutrophils and platelets, low incidences of acute and chronic GVHD, and favorable long-term outcomes using single CB units with relatively low cell content. Moreover, CB cell dose had no impact on CB engraftment and survival in this study. Therefore, haplo-cord SCT expands donor availability while reducing CB cell dose requirements.

Monoanchoring (D‐D‐π‐A) and Dianchoring (D‐D‐(π‐A)2) Organic Dyes Featuring Triarylamine Donors Composed of Fluorene and Carbazole

AbstractOrganic dyes containing carbazole as an auxiliary donor, oligothiophene linkers, and cyanoacrylic acid acceptors with two different architectures (D‐D‐π‐A and D‐D‐(π‐A)2) were synthesized and characterized by optical and electrochemical measurements. The charge‐transfer transitions of the monoanchoring dyes with a D‐D‐π‐A configuration are intense whereas the π–π* transitions of the dianchoring dyes with D‐D‐(π‐A)2 architecture are promising. Incorporation of bithiophene into the conjugation slightly lowers the LUMO level of the dyes. The optical and electrochemical properties of these dyes are better than diphenylamine‐based dyes. The TDDFT calculations were performed to rationalize the trends in the optical and electrochemical properties of the dyes. The efficiency of dye‐sensitized solar cells based on the monoanchoring dyes is two to fivefold larger than the corresponding cells based on dianchoring congeners. Also, the use of chenodeoxycholic acid as an additive increases the efficiency of the devices reasonably.

Quantum Chemical Designing of Novel Organic Non-Linear Optical Compounds

In the present study, ten metal free non-linear optical (NLO) compounds have been designed. These compounds have designed by structural modification of (2-cyano-5-(4-(phenyl(4-vinylphenyl)amino)phenyl) penta-2,4-dienoic acid (TC4). Density functional theory was used for structure optimization and determination of photo-physical properties. These compounds contain triphenylamine as electron-donor and cyanoacrylic acid as acceptor. Five π-spacers are used to connect the donor and acceptor. Two auxiliary donors are also used to assist the donor. Results of this study indicate that stronger electron-donating auxiliary groups and longer πconjugation enhance NLO response. Major absorption peaks of all systems were in the visible region. These absorption peaks are associated with the π-π* transitions of the entire molecule. From calculations it is clear that all system will be good NLO material. The present calculations will provide new ways for experimentalists to synthesize high-performance NLO material.

Regioselective and regiospecific C(naphthyl)–H bond activation: Isolation, characterization, crystal structure and TDDFT study of isomeric cyclopalladates

The C2(naphthyl)–H, C3(naphthyl)–H and C8(naphthyl)–H bonds of the naphthyl group present in a group of naphthylazo-2′-hydroxyarenes (H2L) have been activated at room temperature by palladium(II) and stable cyclopalladates of the type [PdL(B)] have been isolated in presence of neutral Lewis bases (B). The activation of C2(naphthyl)–H and C8(naphthyl)–H bonds of 1-(2′-hydroxynaphthylazo) naphthalene (H2L1) lead to the formation of isomeric cyclopalladates 2a &2b respectively. The single crystal X-ray structures of both the isomers show the naphthylazonaphtholate is coordinated to palladium(II) as a dianionic terdentate C,N,O-donor and Lewis base B occupies the fourth position in the coordination sphere. The ortho-palladate (2a) contains both five-membered carbopalladacycle and azonaphtholato chelate ring whereas a five-membered carbopalladacycle and a six-membered azonaphtholato chelate ring are present in peri-palladate (2b). On the other hand, only C3(naphthyl)–H bond of 2-(2′-hydroxyarylazo)naphthalene (H2L2 & H2L3) has been found to be regiospecifically activated by palladium(II). The role of auxiliary donors on the regioselective and regiospecific C(naphthyl)–H bond activation and the rationale behind the formation of isomeric cyclopalladates have been discussed. All of the cyclopalladates absorb strongly in the ultraviolet and visible region. The Time-dependent density functional theory (TDDFT) calculations reveal that the high energy absorptions are predominantly due to intraligand π–π* and the low energy absorptions originate from intraligand π–π* with a small admixture of metal-to-ligand charge-transfer transitions.

Unsymmetrical squaraine sensitizers containing auxiliary arylamine donor for NIR-harvesting on dye-sensitized solar cell

Developing sensitizers capable of absorbing light intensely in the red to near-IR region is important to improve the performance of dye-sensitized solar cells. In this article, three new squaraine sensitizers containing diarylamines with varied alkyl or alkoxyl chain substituents as auxiliary donors were synthesized and utilized. The effects of different donor tail chains, i.e., methyl, methoxyl and hexyloxy groups on the photophysical, electrochemical and photovoltaic properties were investigated. Results indicated the alkoxyl chains brought about a more broadened photoresponse than the alkyl chain and the long hydrocarbon chain was superior to short chains in suppression of electron recombination. Therefore, with a bis(4-(hexyloxy) phenyl) amine substituent, a squaraine sensitized solar cell presented expansion of the incident photon-to-current conversion from the red to near infrared wavelength region up to 800 nm and hindered electron recombination, resulting in an efficiency of 3.39% under AM 1.5 irradiation.

Organic dyes with imidazole derivatives as auxiliary donors for dye-sensitized solar cells: Experimental and theoretical investigation

In order to study the influence of different imidazole derivatives in triphenylamine-based organic dyes, two different imidazole derivatives are introduced into the phenyl ring of the triphenylamine core, coded as CD-4 and CD-6, respectively. Their photophysical, electrochemical properties and the performances of the corresponding dye-sensitized solar cells (DSSCs) are further investigated. Due to the better molar extinction coefficient, quantum efficiency (QE) and longer lifetime of excited electron, the DSSC based on CD-4 has the higher overall conversion efficiencies as 4.11% than that of CD-6 as 1.51% under full sunlight (AM 1.5G, 100 mW cm−2) irradiation. Density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations were carried out to study the ground state structures, the electronic structures and the optical properties of the two dyes. The simulated UV–vis absorption spectra for the two dyes are in excellent agreement with the experimental results.

Tuning the electron donating ability in the triphenylamine-based D-π-A architecture for highly efficient dye-sensitized solar cells

A new series of triphenylamine-based organic dye sensitizers, namely TPA1-TPA6 with introduced auxiliary donor groups including carbazole and diphenylamine moieties to triphenylamine core, and with inserted fluorene moiety between triphenylamine and auxiliary donor, was designed and theoretically investigated. The starburst triphenylamine dyes acting as electron donor groups capped with mono- and di-substituted auxiliary donors coded as D-D-π-A and 2D-D-π-A respectively, were studied for the propose of comparison with only one triphenylamine moiety as donor, namely TPA, in the D-π-A system. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were conducted to investigate the molecular structures, frontier molecular orbitals, absorption spectra as well as dye-(TiO2)38 complexes of these dyes as implemented in the Gaussian 09 program. Among three dye architectures, the results suggested that the 2D-D-π-A system showed the largest absorption range. We found that different types of auxiliary donors provided different light-harvesting ability; the diphenylamine auxiliary donor can improve properties of red-shifted absorption region. In addition, the optimized geometries showed that adding of diphenylamine auxiliary donor provided smaller external dihedral angles (EDA) leading to wider absorption range with strong charge-transfer character compared to other dyes. Our results are suggested to be the possible reasons for the enhancement of conversion efficiency in dye-sensitized solar cells.

Quantum Chemical Designing of Efficient TC4-Based Sensitizers by Modification of Auxiliary Donor and π-Spacer

Abstract In the present study, ten metal-free dyes for dye-sensitized solar cells (DSSCs) have been designed. These dyes have designed by structural modification of TC4. Density functional theory was used for structure optimization and determination of photophysical properties. These dyes contain triphenylamine as electron donor and cyanoacrylic acid as electron acceptor. Five π-spacers are used to connect the donor and acceptor. Two auxiliary donors are also used to assist the donor. Results of this study indicate that stronger electron-donating auxiliary groups and longer π-conjugation enhance, while electron-withdrawing fluorine at a π-spacer decreases the performance of dyes in DSSC. As compared to auxiliary electron donors, π-spacers have a strong impact on the performance of the dyes in the DSSCs. Major absorption peaks of all dyes were in the visible region. These absorption peaks are associated with the π–π* transitions of the entire molecule. From calculations it is clear that all dyes will be good photosensitizers in DSSC. The present calculations will provide new ways for experimentalists to synthesize high-performance dyes.