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Instrumentation: 1 H NMR and 13 C NMR spectra were measured in deuterated chloroform using a Bruker DRX 400 and a Bruker AC 250. Chemical shifts (δ values) are given in part per million with tetramethylsilane as an internal standard. Elemental analysis was performed on a CHNS-932 Automat Leco. Differential scanning calorimetry (DSC) measurements were carried out on a Mettler DSC 30 with a cell purged with nitrogen. Calibration for temperature and enthalpy changes was performed using an Indium standard. The temperature was changed between 0 and 250 o C with a heating/cooling rate of 10 K/min. In total two heating-cooling cycles were performed on each sample. Thermogravimetric analysis (TGA) was performed on a Mettler TA-300-thermal analyzer operating under air atmosphere. The samples were heated from 0 to 700 °C with a heating rate of 10 K/min. Gel permeation chromatography was performed on a set of Knauer using THF as eluent and polystyrene as standard. The absorption spectra were recorded in dilute chloroform solution (c ≈ 10-6 mol l-1) on a Perkin-Elmer UV/VIS-NIR Spectrometer Lambda 19. Quantum-corrected emission spectra were measured in dilute chloroform solution with a LS 50 luminescence spectrometer (Perkin-Elmer). The solution photoluminescence quantum yields were calculated either according to Demas and Crosby against quinine sulfate in 0.1 N sulfuric acid as a standard (Φ f = 55%) 1 or in ethanol against rhodamine 6G standard (Φ f = 95%). Thin film (from CHCl 3 solution) absorption and emission spectra were measured with a Hitachi F-4500 Fluorescence Spectrophotometer. Their absolute photoluminescence quantum yields were measured in an intergrating sphere. The absorption spectra of thin film from chlorobenzene solution were recorded on Varian UV/Vis spectrophotometer and the corresponding emission spectra were recorded on a home-built photoluminescence setup. Thin films were spin coated on glass substrates using chlorobenzene based solutions (0.6-0.8 wt %). Infrared spectroscopy was recorded on a Nicolet Impact 400. Cyclic voltammetry (CV) was performed with a PA4 polarographic analyzer (Laboratory Instruments, Prague, CZ) with a

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The design of novel conjugated polymers suitable for use in plastic solar cells is one of today's challenges aiming towards improved key properties like the increase of photocurrent and open circuit voltage of such devices. In this work we present first results on arylene-ethynylene/arylene-vinylene hybrid polymers 3 (poly(-2,5-dioctyloxy-1,4-phenylene-diethynylene-2,5-dioctyloxy-1,4-phenylene-vinylene-2,5-di(2'-ethyl)hexyloxy-1,4-phenylene-vinylene)) and 5 (poly(2,5-dioctyloxy-1,4-phenylene-ethynylene-9,10-anthracenylene-ethynylene-2,5-dioctyloxy-1,4-phenylene-vinylene-2,5-di(2'-ethyl)hexyloxy-1,4-phenylene-vinylene)), demonstrating photovoltaic action in combination with the soluble C 60 derivative 1-(3-methoxycarbonyl) propyl-1-phenyl [6,6]C 61 (PCBM). Devices with an active layer thickness of about 100 nm yielded power conversion efficiencies of up to 2% under 100 mW cm 22 AM 1.5 white light illumination. The coarse grained morphology of the active layers was identified as the main limitation for the photocurrent, revealed by AFM measurements. The photovoltaic devices were characterized by current-voltage and spectral photocurrent measurements. The results show that the open circuit voltage is weakly dependent on the HOMO (highest occupied molecular orbital) level of the conjugated polymer used as donor.{ Electronic supplementary information (ESI) available: IR spectrum of polymer 5. See

The Horner-Wadsworth-Emmons olefination reaction of luminophoric dialdehydes 1 and 2 and bisphosphonates 3 provide high-molecular-weight and thermostable PPV/PPE hybrid polymers 4 and 5 of well-defined general constitutional structure -(CHdCH-Ph-CHdCH-Ph-CtC-Ph-CtC-Ph-) n, which was confirmed by NMR, infrared and elemental analysis. Soluble and good film-forming materials were obtained after attaching long linear alkoxy, e.g., dodecyloxy, octadecyloxy, or branched alkoxy side chains, e.g., 2-ethylhexyloxy, on the conjugated backbone. Thermotropic and lyotropic liquid crystalline behavior was observed with polarized optical microscopy. The presence of triple bonds along the PPV backbone increases the electron affinity of these polymers, which is reflected by the comparatively (with MEH-PPV) higher oxidation potential of 1.30 V vs Ag/AgCl. Polymers 4 and 5 are good photoconducting and highly luminescent materials. While almost identical photophysical behaviors for all polymers of type 4 (λ max,abs ) 450 nm, λmax,em ) 490 nm) or 5 (λmax,abs ) 470 nm, λmax,em ) 553 nm) were obtained in dilute chloroform solution, resulting in fluorescence quantum yields between 70 and 80% of the yellowish-green emission, the solid-state properties (color, thermal behavior, photoconductivity, absorption and emission spectra, and photoluminescence quantum yields) are dependent on the size, geometry, number, and location of the grafted alkoxy side groups. Exchanging for example the position of the side chains from 4ac) leads not only to a change in color of the material from orange to yellow but also a dramatic change in the photophysical behavior. In general, octadecyloxy side chains in position R 4 are necessary to obtain narrow and structured emission curves, small Stokes shifts, less excimer formation, and higher fluorescence quantum yields (30-40%). The fully substituted, deep orange-red polymer 5a (R 2 ) R 4 ) O(CH2)17CH3), for example, behaves as if its conjugated backbone was dissolved in a hydrocarbon solvent. This is confirmed by its very high photocurrent of 1.1 × 10 -9 A (which is at least 2 orders of magnitude higher than that of all the other polymers), detected at the lowest threshold voltage of 10 V, and its highest φfl value of 54%. It can be assumed from these facts that photoconductivity is more an intramolecular phenomenon than an intermolecular one. Strong π-π interchain interactions not only lead to fluorescence quenching through excimer formation but also have a negative effect on photoconductivity.

High-molecular-weight, soluble and thermostable alkoxy-substituted arylene−ethynylene/arylene−vinylene conjugated polymers, 13 and 14, have been successfully synthesized through the Horner−Wadsworth−Emmons olefination of luminophoric dialdehydes 7 and 9 and bisphosphonate 12 in very good yields. They were characterized through 1H NMR, 13C NMR, IR, and elemental analysis. The investigation of their photophysical and electrochemical properties has been carried out. Although almost identical absorption and emission spectra were obtained in dilute chloroform solution for all polymers 13, the full width at half-maximum (fwhm) value of the emission curves depends on the length of the attached side chains. The presence of anthracenylene units in 14 leads to a red shift of its absorption and emission spectra relative to 13. Strong self-reabsorption after excitation in solution was observed for this polymer. The solid-state photophysical properties of 13 and 14 (photoconductivity, absorption and emission spectra, fluorescence quantum yield, Stokes shift, and fwhm) greatly depend on the nature (linear or branched), length, and location of the grafted alkoxy side groups. Photoconductivity is easily detected in polymers having octadecyloxy chains (13aa, 13ab, 14). Long linear (octadecyl, i.e., 13aa) or short branched (2-ethylhexyl, i.e., 13 cc) side chains at position R2 (phenylene−vinylene segment) are necessary to obtain sharp and well-resolved emission spectra accompanied by high fluorescence quantum yields. The quasi-donor (phenylene−vinylene segment)−acceptor (arylene−ethynylene segment) nature of these polymers could explain the great discrepancy between the electrochemical band gap energy, E g ec ≈ 1.60 eV, as obtained from the onset values of the redox potentials in cyclic voltammetry and in differential pulse polarography measurements, and the optical band gap energy, E g opt ≈ 2.30 eV, from the absorption spectra.

Alkoxy-substituted CN-containing phenylene−vinylene−alt-phenylene−ethynylene hybrid polymers (CN−PPV−PPE), 3a, 3b, and 7a, were obtained from luminophoric dialdehydes 1 by step growth polymerization via Knoevenagel reaction as high molecular-weight materials. Corresponding CN-free polymers 3c and 7b and an ethynylene-free polymer 5 with similar side chains were synthesized for the purpose of comparison. The chemical structures of the polymers were confirmed by IR, 1H and 13C NMR, and elemental analysis. Thermal characterization was conducted by means of thermogravimetric analysis and differential scanning calorimetry. Morphology was investigated by means of optical microscopy and small-angle light scattering. The final morphologies are determined by the molecular characteristics (side chains volume fraction, backbone stiffness) of the studied polymers. All the CN-containing polymers 3b, 5, and 7a exhibit higher fluorescence quantum yield in solid state (50 to 60%), but lower quantum yields (12−40%) in dilute chloroform solution, in total contrast to CN-free polymers 3c, 3d, and 7b. Identical optical, E g opt, and electrochemical band gap energies, E g ec, were obtained for 3b, 3c and 3d with intrinsic self-assembly ability, whereas a discrepancy, ΔE g, was observed in the cases of the fully substituted polymers 5, 7a, and 7b, whose values are dependent on the level of backbone stiffness and length of the side groups combined with the presence or absence of CN units. The incorporation of CN units in 3b and 7a lowers their respective LUMO level by 220 and 350 meV compared to their corresponding CN-free counterparts 3c and 7b, suggesting an improvement of the electron-accepting strength. Polymers 3b and 7a are efficient electron acceptors suitable for photovoltaic application. The experiments indicate that 3b is a better electron acceptor when used together with M3EH−PPV, but transport properties seem to be better for 7a. With 3b, high external quantum efficiencies of up to 23%, an open circuit voltage of up to 1.52 V, and a white light energy efficiency of 0.65% could be realized in bilayer solar cell devices. LED-devices of configuration ITO/PEDOT:PSS/polymer/Ca/Al from 3b, 3c, 7a, and 7b showed low turn-on voltages between 2 and 2.5 V. The CN-free polymers 3c and 7b exhibit far better EL parameters than their corresponding CN containing counterparts 3b and 7a.