Investigation of chromophore-chromophore interaction by electro-optic measurements, linear dichroism, x-ray scattering, and density-functional calculations

Abstract

Free-beam interferometry and angle-resolved absorption spectra are used to investigate the linear electro-optic coefficients and the linear dichroism in photoaddressable bis-azo copolymer thin films. From the first- and second order parameters deduced, the chromophore orientation distribution is calculated and displayed for several poling temperatures and chromophore concentrations. The influence of dipole-dipole interaction on the overall polymer dynamics is discussed. The first order parameter, and therefore the Pockels effect, peaks for a poling temperature of around 10 degrees C above the glass transition. The decrease of the Pockels effect above this temperature region is triggered by a head-to-tail chromophore orientation, i.e., a transition to a microcrystalline phase, increasing the second order parameter. Comparison of the experimentally observed absorption spectra and those obtained by density-functional calculations support the picture of differently aligned bis-azo dye molecules in a trans,trans configuration. Complementary wide-angle x-ray scattering is recorded to confirm the various kinds of ordering in samples poled at different temperatures.

Aqueous Processing of Low-Band-Gap Polymer Solar Cells Using Roll-to-Roll Methods

“…The reduced 1D data were analyzed by using the Bayesian inverse Fourier transform (BIFT). 19 GIWAXS of spin-coated films on glass were acquired by orienting the substrate surface just below the critical angle for total reflection with respect to the incoming X-ray beam (0.18°), maximizing scattering from the deposited film with respect to scattering from the substrate. In the wide scattering angle range (>5°), the X-ray scattering is sensitive to crystalline structure.…”

“…For the experiment we used a camera comprising an evacuated sample chamber with an X-ray photosensitive image plate as detector and a rotating Cuanode operating at 50 kV/200 mA as X-ray source, focused and monochromatized (Cu KR, λ = 1.5418 Å) by a 1D multilayer. 19 The samples were mounted 120 mm from the detector. The GIWAXS data were analyzed by reducing the acquired 2D data by azimuthal averaging of intensity as a function of scattering vector length, q, to determine the characteristic d-spacings of the polymers, using the software SimDiffraction.…”

High‐Performance Ambipolar Diketopyrrolopyrrole‐Thieno[3,2‐b]thiophene Copolymer Field‐Effect Transistors with Balanced Hole and Electron Mobilities

“…The GIWAXS measurements were performed at RISØ National Laboratory. [37] The X-ray energy was 8 keV and the incidence angle was chosen as 0.18°. The AFM images were obtained using a Digital Instruments Dimension 3100 AFM in tapping mode.…”

Patterning and Conductivity Modulation of Conductive Polymers by UV Light Exposure

“…The measurements were performed using a dedicated GIWAXS setup, described by Apitz et al [15] , using a rotating Cu anode as X-ray source, collimated and monochromatized by a multilayer mirror (wavelength 1.5418 Å). The substrates were aligned to an incidence angle of 0.18°, below the critical angle for total reflection for the silicon wafer, and the scattered data were recorded on photostimulable imaging plates.…”