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...

Microcavities filled with biologically produced green fluorescent protein show polariton condensation at room temperature.

We report on a laser that is fully embedded within a single live cell. By harnessing natural endocytosis of the cell, we introduce a fluorescent whispering gallery mode (WGM) microresonator into the cell cytoplasm. On pumping with nanojoule light pulses, green laser emission is generated inside the cells. Our approach can be applied to different cell types, and cells with microresonators remain viable for weeks under standard conditions. The characteristics of the lasing spectrum provide each cell with a barcode-type label which enables uniquely identifying and tracking individual migrating cells. Self-sustained lasing from cells paves the way to new forms of cell tracking, intracellular sensing, and adaptive imaging.

Traditional low-molecular weight colorants that are widely applied in textile coloration, for printing purposes and nonlinear optics, now afford bulk heterojunction solar cells in combination with soluble C(60) fullerene derivative PCBM with power conversion efficiencies up to 1.7% under standard solar radiation.

The UV/vis spectra were measured with a JASCO V-550 UV-Vis spectrophotometer, the emission spectra with a CARY Eclipse fluorescence spectrophotometer. IR spectra were recorded on a JASCO FT/IR-4200 Fourier Transform spectrometer. NMR spectra ( 1 H and 13 C) were measured with a Bruker ARX 400 spectrometer using solutions in CDCl 3 ; J values are given in Hz. Mass spectra were obtained using a Varian MAT 311A instrument with an electro spray ionization source (ESIMS). The microwave-assisted synthesis was carried out in a Discover reaction unit (CEM) using sealed reaction vials. The temperature inside the vial was monitored by an IR sensor; the pressure by a hydraulic system. The polymerizations were performed under temperature control with a maximum microwave power of 300 W. MaterialsAll reactions were carried out under an argon atmosphere using the usual Schlenk techniques.TLC was carried out on dry silica gel plates. For liquid chromatography, silica gel with a pore size 0.06-0.2 nm was used. All solvents were of reagent grade and used as received, unless otherwise specified. 5,8-Dibromo-2,3-dioctylquinoxaline, 1 4,4-bis(2-ethylhexyl)-2,6bis(trimethylstannyl)-4H-cyclopenta- [2,1-b:3,4-b`]dithiophene 2-4 , 2-(tri-n-butylstannyl)thiophene, 5 and 4,7-dibromobenzo-2,1,3-thiadiazole 6 were prepared according to literature procedures. Synthesis 4,7-Bis(thiophen-2-yl)benzo-2,1,3-thiadiazole 4,7-Dibromobenzo-2,1,3-thiadiazole (17.01 mmol, 5 g), 2-(tri-n-butylstannyl)thiophene (37.4 mmol, 13.96 g), KF (136 mmol, 7.91 g) and PdCl 2 (PPh 3 ) 2 (1.36 mmol, 0.955 g) were placed in a 100 ml-Schlenk tube. After addition of dry THF (100 ml) the reaction mixture was stirred for 48 h at 80 °C. Then, the reaction mixture was poured into chloroform (200 ml). The organic phase was washed with water (2 × 200 ml), dried over anhydrous MgSO 4 and the solvent removed under reduced pressure. Purification by column chromatography (silica gel, toluene/n-hexane 1/4 v/v) gave 2.19 g (7.29 mmol; 42.9 %) of red crystals.

No abstract

Cellular forces are crucial for many biological processes but current methods to image them have limitations with respect to data analysis, resolution and throughput. Here, we present a robust approach to measure mechanical cell-substrate interactions in diverse biological systems by interferometrically detecting deformations of an elastic micro-cavity. Elastic resonator interference stress microscopy (ERISM) yields stress maps with exceptional precision and large dynamic range (2 nm displacement resolution over a >1 μm range, translating into 1 pN force sensitivity). This enables investigation of minute vertical stresses (<1 Pa) involved in podosome protrusion, protein-specific cell-substrate interaction and amoeboid migration through spatial confinement in real time. ERISM requires no zero-force reference and avoids phototoxic effects, which facilitates force monitoring over multiple days and at high frame rates and eliminates the need to detach cells after measurements. This allows observation of slow processes such as differentiation and further investigation of cells, for example, by immunostaining.

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.