Challenging the auxiliary donor effect on molecular hyperpolarizability in thiophene-containing nonlinear chromophores: X-ray crystallographic and optical measurements on two new isomeric chromophores

To reexamine the established "auxiliary donor" effect of thiophene in nonlinear optical (NLO) chromophores, we have prepared two isomeric donor-acceptor azo dyes, differing only in the position of the thiophene. Experimental analysis of these chromophores, including electric field-induced second harmonic generation (EFISH) and X-ray crystallography, contradicts previous experimental findings on similar chromophores but is consistent with the majority of computational precedents. We have found that the thiophene on the donor side produces a compound with a larger dipole moment; however, the isomer with the thiophene on the acceptor side is more nonlinear and has a higher figure of merit for NLO device applications.     

Simple organic molecules bearing a 3,4-ethylenedioxythiophene linker for efficient dye-sensitized solar cells

3,4-Ethylenedioxythiophene and bis[2-(2-methoxyethoxy)ethoxy]thiophene bridged donor-acceptor molecules for dye-sensitized solar cells have been synthesized, one of which achieved a solar-to-energy conversion efficiency of 7.3%, compared to 7.7% optimized for N719 dye.     

Diindenothieno[2,3-b]thiophene arene for efficient organic photovoltaics with an extra high open-circuit voltage of 1.14 ev

We report a novel diindenothieno[2,3-b]thiophene ladder-type hexacyclic arene for constructing a donor-acceptor copolymer PDITTDTBT. A device based on PDITTDTBT:PC(71)BM exhibited a high V(oc) of 0.92 V with an impressive PCE of 5.8%, while a PDITTDTBT:DMPCBA-based device showed an extra high V(oc) of 1.14 V.     

Dithienothiophene (DTT)-based dyes for dye-sensitized solar cells: synthesis of 2,6-dibromo-DTT

A one-pot synthesis of 2,6-dibromodithieno[3,2-b;2',3'-d]thiophene (dibromo-DTT, 4) was developed. A key step was bromodecarboxylation of DTT-2,6-dicarboxylic acid, obtained by saponification of the diester 1. The donor-acceptor dye DAHTDTT (13), based on a central 2,6-bis[2'-(3'-hexylthienyl)]dithieno[3,2-b;2',3'-d]thiophene core (9), was prepared and incorporated in a dye-sensitized solar cell (DSC), which exhibited an energy conversion efficiency of 7.3% with V(oc) of 697 mV, J(sc) of 14.4 mA/cm(2), and ff of 0.73 at 1 sun.     

Synthesis of Polymers Containing Second Order NLO-Active Thiophene and Thiazole Based Chromophores

Grounding on the evidence that thiophene or thiazole rings in donor-acceptor chromophoric systems promote enhancement of charge transfer and nonlinear optical responses, in this work NLO properties have been investigated of organic polymers containing azoic chromophores based on dinitrothiophene or nitrothiazole moieties. It has been carried out the azo coupling reaction directly between a series of copolymers and diazonium salts containing the etherocyclic group at different grafting percentages.     

An isoindigo-based low band gap polymer for efficient polymer solar cells with high photo-voltage

A new low band gap polymer (E(g) = 1.6 eV) with alternating thiophene and isoindigo units was synthesized and characterized. A PCE of 3.0% and high open-circuit voltage of 0.89 V were realized in polymer solar cells, which demonstrated the promise of isoindigo as an electron deficient unit in the design of donor-acceptor conjugated polymers for polymer solar cells.     

Donor-acceptor copolymers from cyclopentannulation polymerizations with dicyclopenta[cd,jk]pyrene and dicyclopenta[cd,lm] perylene acceptors

A series of donor-acceptor copolymers with dicyclopenta[cd,jk]pyrene and dicyclopenta[cd,lm]perylene acceptor units was prepared via palladium catalyzed cyclopenta-annulation reactions. The acceptor units were paired with diethynyl containing donor groups based on benzo[1,2-b:4,5-b’]dithiophene, thieno[3,2-b]thiophene, and 4-octyl-4H-dithieno[3,2-b:2′,3′-d]pyrrole to create six polymer variants. The cyclopentannulation polymerization resulted in copolymers with molecular weights (Mn) of 6–14 kDa and broad light absorption in the visible region with band gaps of 1.38–1.85 eV. The synthetic methodology, as well as optoelectronic properties, including thin-film absorption and cyclic voltammetry, of the donor-acceptor copolymers are presented.     

Synthesis of soluble donor-acceptor double-cable polymers based on polythiophene and tetracyanoanthraquinodimethane (TCAQ)

[structure: see text] Novel suitably functionalized tetracyanoanthraquinodimethane (TCAQ) derivatives covalently linked to thiophene moieties have been synthesized. The thiophene-based monomers have been chemically polymerized and copolymerized to yield new and soluble donor-acceptor double-cable polymers. The absorption and emission data reveal that the optical properties can be finely tuned by modifying the ratio of monomers in the copolymerization process.     

Cyclic donor-acceptor circuits: synthesis and fluorescence ion sensory properties of a mixed-heterocyclic dehydroannulene-type cyclophane

The new dehydroannulene-type cyclophane 5 comprising a conjugated helical framework of thiophene (electron donor) and pyridine (electron acceptor) heterocyclic units has been prepared. Macrocycle 5 was characterized by FAB MS and (1)H and (13)C NMR spectroscopy. Cycle 5 was found to function as a selective precipitation and fluorescence sensor for specific metal ions such as Ag(I) and also exhibited reversible proton-triggered fluorescence quenching behavior. The unique donor-acceptor architecture and spectroscopic properties of 5 suggest that it represents a novel lead class of molecular sensory platforms, with many potential future applications in 21st century materials science.     

Macrocyclic Donor-Acceptor Dyads Composed of Oligothiophene Half-Cycles and Perylene Bisimides

A series of donor-acceptor (D−A) macrocyclic dyads consisting of an electron-poor perylene bisimide (PBI) π-scaffold bridged with electron-rich α-oligothiophenes bearing four, five, six and seven thiophene units between the two phenyl-imide substituents has been synthesized and characterized by steady-state UV/Vis absorption and fluorescence spectroscopy, cyclic and differential pulse voltammetry as well as transient absorption spectroscopy. Tying the oligothiophene strands in a conformationally fixed macrocyclic arrangement leads to a more rigid π-scaffold with vibronic fine structure in the respective absorption spectra. Electrochemical analysis disclosed charged state properties in solution which are strongly dependent on the degree of rigidification within the individual macrocycle. Investigation of the excited state dynamics revealed an oligothiophene bridge size-dependent fast charge transfer process for the macrocyclic dyads upon PBI subunit excitation.     

D-A型共轭低聚物的电子性质及D-A比对其影响的理论研究

以[1,2,5]噻重氮并[3,4-g]喹喔啉(TQ)为受体、 噻吩(Th)、 噻吩并[3,2-b]噻吩(TTh)和吡咯(Py)为供体, 设计了6类供体-受体(D-A)型共轭低聚物. 采用杂化的密度泛函方法(B3LYP), 研究了此6类低聚物的电子结构和性质. 电子密度拓朴分析和核独立化学位移计算表明, 随着聚合度的增加, 体系共轭程度增强, HOMO-LUMO能级差逐渐减小. 同时, 随着聚合度的增加, 低聚物电离能减小, 电子亲和势增大. 供体-受体摩尔比(D-A比)对低聚物的性质有重要影响, 提高D-A比能有效地增大分子内电荷迁移, 从而使HOMO-LUMO能级差减小. Py不仅是一个强的电子供体, 还是一个潜在的氢键供体. 在含Py结构单元的低聚物中, 由于分子内氢键的存在使其具有较大的分子内电荷迁移值. 所设计的6种基于TQ的四聚体均具有较小的HOMO-LUMO能级差(<1 eV), 使其相应的聚合物的能隙更小, 可作为潜在的性能优良的导电材料.     

Dynamic Monte Carlo modeling of exciton dissociation in organic donor-acceptor solar cells

A general dynamic Monte Carlo model for exciton dissociation at a donor-acceptor interface that includes exciton delocalization and hot charge separation is developed to model the experimental behavior observed for the poly(3-hexylthiophene):fullerene system and predict the theoretical performance of future materials systems. The presence of delocalized excitons and the direct formation of separated charge pairs has been recently measured by transient photo-induced absorption experiments and has been proposed to facilitate charge separation. The excess energy of the exciton dissociation process has also been observed to have a strong correlation with the charge separation yield for a series of thiophene based polymer:fullerene systems, suggesting that a hot charge separation process is also occurring. Hot charge separation has been previously theorized as a cause for highly efficient charge separation. However, a detailed model for this process has not been implemented and tested. Here, both conceptual models are implemented into a dynamic Monte Carlo simulation and tested using a simple bilayer donor-acceptor system. We find that exciton delocalization can account for a significant reduction in geminate recombination when compared to the traditional, bound polaron pair model. In addition, the hot charge separation process could further reduce the geminate recombination, but only if the hot charge mobility is several orders of magnitude larger than the standard charge mobility.     

含噻吩环的吡啶Ru(II)配合物的电子结构和非线性光学性质

采用密度泛函理论(DFT) B3LYP方法对含有噻吩环的吡啶Ru(II)配合物的电子结构和非线性光学(NLO)性质进行理论研究. 结果表明: 配合物[Ru^II(NH₃)₅L]²⁺(L为含噻吩环的有机基团)中, 配位原子与中心金属离子间没有形成稳定的化学键, 但存在较强的供体-受体(D-A)相互作用; NH₃被羰基(CO)取代后, Ru-C间形成了稳定的σ-π配键, 降低了受体的空轨道能级. 噻吩环的增加增大了体系的共轭程度, 有利于分子内电荷转移, 使配合物的极化率α和一阶超极化率β明显增加. 结合配合物的前线分子轨道分析发现, 电荷转移过程中, 对体系二阶NLO系数贡献较大的是配体内电荷转移(ILCT)和配体间电荷转移(LLCT)跃迁, 羰基引入后配体到金属的电荷转移(LMCT)使配合物[Ru^II(CO)₅L]²⁺比对应的配合物[Ru^II(NH₃)₅L]²⁺的β值增大约7倍.     

All-polymer solar cells with perylenediimide polymer acceptors

Four polymers based on perylenediimide co-polymerized with thiophene, bithiophene, selenophone and thieno[3,2-b]thiophene were investigated as the acceptor materials in all-polymer solar cells. Two different donor polymers, poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene)-2-carboxylate-2,6-diyl](PTB7-Th) and poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3′′′-di(2-dodecyltetradecyl)-2,2′;5′,2″;5″,2′′′-quaterthiophen-5,5′′′-diyl)](Pff BT4T-2DT), with suitably complementary absorption spectra and energy levels were applied and examined. Among all different donor-acceptor pairs studied here, the combination of PTB7-Th:poly[N,N′-bis(1-hexylheptyl)-3,4,9,10-perylenediimide-1,6/1,7-diyl-alt-2,5-thiophene](PDI-Th) exhibited the best power conversion efficiency(PCE) of 5.13%, with open-circuit voltage(V_(oc)) = 0.79 V, short-circuit current density(J_(sc)) = 12.35 mA·cm~(-2) and fill-factor(FF) = 0.52. The polymer of PDI-Th acceptor used here had a regio-irregular backbone, conveniently prepared from a mixture of 1,6- and 1,7-dibromo-PDI. It is also noteworthy that neither additive nor posttreatment is required for obtaining such a cell performance.     

Quantum-chemical investigation of second-order nonlinear optical chromophores: comparison of strong nitrile-based acceptor end groups and role of auxiliary donors and acceptors

We report a detailed quantum-chemical investigation of donor-acceptor substituted dipolar nonlinear optical chromophores incorporating the 4-(dimethylamino)phenyl donor end group and a variety of strong heterocyclic acceptor end groups, including tricyanofurans and tricyanopyrroles. In particular, we study the variation of the molecular second-order polarizability (beta) with the acceptor end group and when inserting auxiliary donors (thiophene) and acceptors (thiazole) into the pi bridge. Both finite-field calculations (in the context of local contributions) and sum-over-states calculations were carried out in order to probe the relationship between beta and the chemical structure of the various chromophores. The trends obtained with these two methods are fully consistent. The large beta values (up to 700 x 10(-30) esu) as well as the observed tunability of the optical absorption maximum (lambda(max)) make the chromophores investigated here interesting candidates for use in electro-optic applications at telecommunications wavelengths.     

供体-受体型共轭聚合物电子结构和导电性能的理论设计

以苯并[1,2-c:4,5-c']二[1,2,5]噻重氮和吡嗪并[2,3-g]喹喔啉为电子受体(A),噻吩、噻吩并[3,2-b]噻吩和二噻吩并[2,3-b:2',3'-d]噻吩为电子供体(D),设计了6种D-A型共轭聚合物.采用B3LYP方法,研究了这6种聚合物的几何结构和电子性质.D-A型共轭聚合物的几何结构和电子结构与电子供体和电子受体的性质,特别是与其提供电子和接受电子的能力密切相关.聚合物的能隙主要受键长交替控制,键长交替越小,能隙越窄.所设计的6种聚合物中,p-BBT-TT具有较窄的能隙(0.48 eV)、较小的载流子有效质量和相对较大的能带宽度,具备理论上的良好导电性能,可能是潜在的优良导电聚合物材料.     

Time-dependent density functional theory investigations on structural modification in carbazole-based organic photosensitizers to improve electron injection in dye-sensitized solar cell

The time-dependent density functional theory approach, implemented at hybrid-B3LYP, GGA-PBE, and density functional-based tight binding levels of theory, was used to model photoinjection in organic dye/TiO₂ quantum dot to explore the prospects of improvement of dye-sensitized solar cell (DSSC). The photosensitizer used in this study consisted of six carbazole-based organic dyes, a cyanoacrylic acid group as an acceptor and an oligothiophene π-bridge spacer. The modifications were made in the dyes by increasing the length of the spacer by adding thiophene and oxadiazole rings at different positions of the donor-acceptor bridge. The structural variations appeared to alter the electronic and optical properties of dyes studied via energy levels and excitation spectra. The UV-Vis spectra calculated for all the dyes in solvents exhibited a red shift in spectral peaks with an increase in the polarity of the solvents. The findings of the study pointed toward the indirect photoinjection of the dye-(TiO₂)₉₆ complex for six different dyes. The substitution of the oxadiazole ring at the center and addition of a thiophene ring at the edge of the spacer produced two dyes that exhibited the lowest injection energies of 0.11 and 0.17 eV, along with the regeneration energies of 1.18 and 1.12 eV, respectively. The dyes reported here may have promising applications in photoanode for enhancing the performance of DSSC.     

Effect of furan π-bridge on the photovoltaic performance of D-A copolymers based on bi(alkylthio-thienyl)benzodithiophene and fluorobenzotriazole

The medium band gap donor-acceptor(D-A) copolymer J61 based on bi(alkylthio-thienyl)benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit and thiophene as π-bridge has demonstrated excellent photovoltaic performance as donor material in nonfullerene polymer solar cells(PSCs) with narrow bandgap n-type organic semiconductor ITIC as acceptor.For studying the effect of π-bridges on the photovoltaic performance of the D-A copolymers,here we synthesized a new D-A copolymer J61-F based on the same donor and acceptor units as J61 but with furan π-bridges instead of thiophene.J61-F possesses a deeper the highest occupied molecular orbital(HOMO) level at-5.45 eV in comparison with that(-5.32 eV) of J61.The non-fullerene PSCs based on J61-F:ITIC exhibited a maximum power conversion efficiency(PCE) of 8.24%with a higher open-circuit voltage(V_(oc)) of 0.95 V,which is benefitted from the lower-lying HOMO energy level of J61-F donor material.The results indicate that main chain engineering by changing π-bridges is another effective way to tune the electronic energy levels of the conjugated D-A copolymers for the application as donor materials in non-fullerene PSCs.     

The molecular and crystal structure of stable 5-methyl-2-methylsulfonyl-3-thiophenecarbonitrile oxide

A stable thiophene derivative, 5-methyi-2-methylsulfonyl-3-thiophenecarbonitrile oxide, which is active in reactions with dipolarophiles, was studied by means of X-ray structural analysis. In the crystalline state the structure includes two independent molecules with similar values of geometric and conformation parameters. The bond angle at the C atom of the nitrile oxide group is significantly different from 180°. The intramolecular distances between the C and S atoms in the nitrile oxide and sulfonyl groups are well below the equilibrium distance. The stability of the molecule is thought to be increased by electrostatic or donor-acceptor interactions between the atoms of these groups. The mutual orientation of the two independent molecules in the crystal is nearly orthogonal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–727, April, 1993.     

噻吩在M(111)(M=Pd,Pt,Au)表面的吸附(英文)

采用密度泛函理论(DFT),选取DMol3程序模块,对噻吩在M(111)(M=Pd,Pt,Au)表面上的吸附行为进行了探讨.通过对噻吩在不同底物金属上的吸附能、吸附构型、Mulliken电荷布居、差分电荷密度以及态密度的分析发现,噻吩在Pd(111)面上的吸附能最大,Pt(111)面次之,Au(111)面最小.吸附后,噻吩在Au(111)面上的构型几乎保持不变,最终通过S端倾斜吸附于top位;噻吩在Pd(111)及Pt(111)面上发生了折叠与变形,环中氢原子向上翘起,最终通过环平面平行吸附于hollow位.此外,噻吩环吸附后芳香性遭到了破坏,环中碳原子发生sp3杂化,同时电子逐渐由噻吩向M(111)面发生转移,M(111)面上的部分电子也反馈给了噻吩环中的空轨道,这种协同作用最终导致了噻吩分子稳定吸附于M(111)面.