Research on small-molecule-based organic semiconductors has undoubtedly been strongly influenced by xerographic photoconductors like triarylamines, the first important organic electronic materials in market products.[1] Their development was strongly influenced by the Bässler model, which provided a rationale for the design of amorphous organic photo-and semiconductors.[2] According to this model, only compounds that lack dipole moments are considered promising for charge-carrier transport because the increased energetic disorder associated with dipole moments is thought to impede charge hopping. Recently, we questioned this paradigm in the field of organic photovoltaics (OPV) and successfully implemented highly dipolar merocyanine dyes as active components for light harvesting as well as exciton and hole transport in solution-cast bulk heterojunction (BHJ) solar cells.[3] The rationale behind our concept [4] was that highly dipolar donor-acceptor (D-A) substituted p systems (also called push-pull dyes) self-assemble into centrosymmetric dimers, [5] thus effectively eliminating molecular dipole moments on the supramolecular and material levels.[6] Two drawbacks of our BHJ materials, however, limited the acceptance of our concept so far. Firstly, the best solar cells were obtained for merocyanine dyes whose molecular scaffolds were equipped with rather bulky substituents that interfere with close face-to-face antiparallel dimerization.[3] Secondly, the power-conversion efficiencies (h) under standard AM1.5, 100 mW cm À2 simulated solar illumination conditions for solution-cast BHJ cells with fullerenes-although significantly advanced by more sophisticated vacuum processing [7] -could not be improved beyond 2.6 %, which is significantly lower than the best solutionprocessed small-molecule-based BHJ devices fabricated with A-D-A and D-A-D chromophores, for example, acceptorsubstituted oligothiophenes (up to 3.7 %) [8] and triarylamines (up to 4.3 %), [9] diketopyrrolopyrroles (up to 4.4 %), [10] and squaraines (up to 5.2 %).[11] Herein, we introduce dipolar D-A dyes with flat structures that undoubtedly form centrosymmetric dimers [5] with perfectly cancelled dipole moments in the solid state. Solution-processed BHJ solar cells derived thereof exhibit power-conversion efficiencies up to 4.5-5.1 % (dependent on light intensity), clearly placing D-A dyes now among the top-performing small molecules in the field of organic photovoltaics.Scheme 1 outlines the synthetic route that follows our earlier work on merocyanine dyes for photorefractive materials [12] and the simple access to 5-dialkylamino-thiophene-2-carbaldehydes by Hartmann.[13] Detailed synthetic procedures and characterization data are described in the Supporting Information.The optical properties of the synthesized dyes were investigated by UV/Vis and electro-optical absorption spectroscopy.[14] Furthermore, cyclic voltammetry was performed for each dye to obtain information about their highest occupied molecular orbital (HOMO) and lowest unoccupied molecu...

In order to be competitive on the energy market, organic solar cells with higher efficiency are needed. To date, polymer solar cells have retained the lead with efficiencies of up to 8%. However, research on small molecule solar cells has been catching up throughout recent years and is showing similar efficiencies, however, only for more sophisticated multilayer device configurations. In this work, a simple, highly efficient, vacuum‐processed small molecule solar cell based on merocyanine dyes – traditional colorants that can easily be mass‐produced and purified – is presented. In the past, merocyanines have been successfully introduced in solution‐processed as well as vacuum‐processed devices, demonstrating efficiencies up to 4.9%. Here, further optimization of devices is achieved while keeping the same simple layer stack, ultimately leading to efficiencies beyond the 6% mark. In addition, physical properties such as the charge carrier transport and the cell performance under various light intensities are addressed.

Research on small-molecule-based organic semiconductors has undoubtedly been strongly influenced by xerographic photoconductors like triarylamines, the first important organic electronic materials in market products.[1] Their development was strongly influenced by the Bässler model, which provided a rationale for the design of amorphous organic photo-and semiconductors.[2] According to this model, only compounds that lack dipole moments are considered promising for charge-carrier transport because the increased energetic disorder associated with dipole moments is thought to impede charge hopping. Recently, we questioned this paradigm in the field of organic photovoltaics (OPV) and successfully implemented highly dipolar merocyanine dyes as active components for light harvesting as well as exciton and hole transport in solution-cast bulk heterojunction (BHJ) solar cells.[3] The rationale behind our concept [4] was that highly dipolar donor-acceptor (D-A) substituted p systems (also called push-pull dyes) self-assemble into centrosymmetric dimers, [5] thus effectively eliminating molecular dipole moments on the supramolecular and material levels.[6] Two drawbacks of our BHJ materials, however, limited the acceptance of our concept so far. Firstly, the best solar cells were obtained for merocyanine dyes whose molecular scaffolds were equipped with rather bulky substituents that interfere with close face-to-face antiparallel dimerization.[3] Secondly, the power-conversion efficiencies (h) under standard AM1.5, 100 mW cm À2 simulated solar illumination conditions for solution-cast BHJ cells with fullerenes-although significantly advanced by more sophisticated vacuum processing [7] -could not be improved beyond 2.6 %, which is significantly lower than the best solutionprocessed small-molecule-based BHJ devices fabricated with A-D-A and D-A-D chromophores, for example, acceptorsubstituted oligothiophenes (up to 3.7 %) [8] and triarylamines (up to 4.3 %), [9] diketopyrrolopyrroles (up to 4.4 %), [10] and squaraines (up to 5.2 %).[11] Herein, we introduce dipolar D-A dyes with flat structures that undoubtedly form centrosymmetric dimers [5] with perfectly cancelled dipole moments in the solid state. Solution-processed BHJ solar cells derived thereof exhibit power-conversion efficiencies up to 4.5-5.1 % (dependent on light intensity), clearly placing D-A dyes now among the top-performing small molecules in the field of organic photovoltaics.Scheme 1 outlines the synthetic route that follows our earlier work on merocyanine dyes for photorefractive materials [12] and the simple access to 5-dialkylamino-thiophene-2-carbaldehydes by Hartmann.[13] Detailed synthetic procedures and characterization data are described in the Supporting Information.The optical properties of the synthesized dyes were investigated by UV/Vis and electro-optical absorption spectroscopy.[14] Furthermore, cyclic voltammetry was performed for each dye to obtain information about their highest occupied molecular orbital (HOMO) and lowest unoccupied molecu...

Phenylazathiacrown ether monostyryl and bis(styryl) dyes were synthesized and their complex forming ability was evaluated in acetonitrile by absorption and fluorescence spectroscopy. It was found that dyes are sensitive to the presence of H+ and Hg2+, Ag+, Cu2+ cations. The most stable complexes were formed with mercury. Stability constants and UV–Vis spectra of complexes defined stoichiometry were determined with the use of HYPERQUAD program. Evidence was given for the occurrence of two stoichiometries: LM and LM2. The pronounced optical response on complex formation was found both in absorption and emission spectra that could be used for optical detection of cations. Copyright © 2008 John Wiley & Sons, Ltd.

New styryl dyes containing azadithia 15 crown 5 fragments were synthesized. The com plexation of these compounds with Ag + , Pb 2+ , Cu 2+ , Hg 2+ , and H + cations was studied by 1 H NMR spectroscopy, steady state, and time resolved spectroscopy. The stability constants of the complexes were calculated from the spectrophotometric titration data. The photophysical properties and E-Z photoisomerization of styryl dyes and their complexes with mercury and copper(II) cations in acetonitrile were examined.A considerable progress in chemistry of macrocyclic compounds is associated not only with their fundamental importance but also with their practical applications in organic synthesis, biology, medicine, and industry. 1-5 Macroheterocyclic sulfur containing compounds (crown compounds, cryptands, catenanes, rotaxanes, and cyclo phanes) have attracted great interest 6-11 because of their ability to selectively form stable complexes with transition and heavy metal cations. These compounds are of consid erable interest as by products in the synthesis of polymers containing thiacrown groups, selective chromogenic and photochromic reagents for metal cations, and extractants for metal salts.The aim of the present study was to synthesize de rivatives of azathiacrown ethers having affinity for heavy and transition metal cations, investigate the complex ation of metal cations with different heteroatoms of the macrocycle, and reveal the influence of complex ation on the optical and photochemical characteris tics of these compounds. Studies of azacrown contain ing styryl dyes demonstrated 12,13 that complexation with rare earth metal cations leads to shifts in absorp tion spectra as large as 50-70 nm. On the one hand, the compounds synthesized and investigated in the present study contain the ionophoric fragment of the phenylazacrown macrocycle, which gives promise that the complexation with metal cations will result in a large optical response. On the other hand, the introduction of sulfur atoms into the macrocycle makes it possible to achieve selective binding with metal salts, which is of