Linear correlation coefficients between ESI responses of anilines with the same substituents at different positions, i.e. <i>ortho-meta-para</i>.

<p>Linear correlation coefficients between ESI responses of anilines with the same substituents at different positions, i.e. <i>ortho-meta-para</i>.</p

Correlations between ESI response and molecular characteristics.

<p>The investigated molecular descriptors were summarized as descriptors of basicity (pKa, pH of 4 mM solution, gas phase basicity, proton affinity, substituent’s electronegativity, and polarizability), polarity (logD, logP, polar/nonpolar/solvent accessible surface area), size (molecular and molar volume, molar mass) and volatility (boiling point, vapor pressure, vaporization enthalpy). A significant linear correlation of signal intensity or ratio with one of the molecular descriptors of each group (basicity, polarity, size and volatility) with a coefficient >0.4 is denoted with “+”, a coefficient >-0.4 with “-“.</p

ESI response of aniline and 4-aminopyridine in presence of different, pH-modifying electrolytes.

<p>Analyses carried out a) by syringe pump infusion in 50% ACN on the API 2000, b) by sample flow injection in 50% ACN on the Esquire 3000+ and c) by sample flow injection in 80% ACN on the Esquire 3000+.</p

Response ratio of the ESI signal intensity at pH 3 and pH 7 in dependency on basicity.

<p>The response of every analyte in aqueous solution (pH 7) is compared to a solution adjusted to pH 3 by formic acid, analyzed for the whole set of analytes in 80% ACN on the API 2000.</p

Signal enhancement by solvent acidification.

<p>Enhancement is more pronounced for compounds with lower boiling points. Response ratio pH 3 / pH 7 plotted over the boiling point, double logarithmic graph.</p

Improving the Resistance of Molecularly Doped Polymer Semiconductor Layers to Solvent

The ability to form multi-heterolayer (opto)electronic devices by solution processing of (molecularly doped) semiconducting polymer layers is of great interest since it can facilitate the fabrication of large-area and low-cost devices. However, the solution processing of multilayer devices poses a particular challenge with regard to dissolution of the first layer during the deposition of a second layer. Several approaches have been introduced to circumvent this problem for neat polymers, but suitable approaches for molecularly doped polymer semiconductors are much less well-developed. Here, we provide insights into two different mechanisms that can enhance the solvent resistance of solution-processed doped polymer layers while also retaining the dopants, one being the doping-induced pre-aggregation in solution and the other including the use of a photo-reactive agent that results in covalent cross-linking of the semiconductor and, perhaps in some cases, the dopant. For molecularly p-doped poly(3-hexylthiophene-2,5-diyl) and poly[2,5-bis(3-tetradecyl-thiophene-2-yl)thieno(3,2-b)thiophene] layers, we find that the formation of polymer chain aggregates prior to the deposition from solution plays a major role in enhancing solvent resistance. However, this pre-aggregation limits inclusion of the cross-linking agent benzene-1,3,5-triyl tris(4-azido-2,3,5,6-tetrafluorobenzoate). We show that if pre-aggregation in solution is suppressed, high resistance of thin doped polymer layers to solvent can be achieved using the tris(azide). Moreover, the electrical conductivity can be largely retained by increasing the tris(azide) content in a doped polymer layer

Thin-Film Texture and Optical Properties of Donor/Acceptor Complexes. Diindenoperylene/F6TCNNQ vs Alpha-Sexithiophene/F6TCNNQ

In this work, two novel donor/acceptor (D/A) complexes, namely, diindenoperylene (DIP)/1,3,4,5,7,8-hexafluoro-tetracyanonaphthoquinodimethane (F6TCNNQ) and alpha-sexithiophene (6T)/F6TCNNQ, are studied. The D/A complexes segregate in form of π–π stacked D/A cocrystals and can be observed by X-ray scattering. The different conformational degrees of freedom of the donor molecules, respectively, seem to affect the thin-film crystalline texture and composition of the D/A mixtures significantly. In equimolar mixtures, for DIP/F6TCNNQ, the crystallites are mostly uniaxially oriented and homogeneous, whereas for 6T/F6TCNNQ, a mostly 3D (isotropic) orientation of the crystallites and coexistence of domains of pristine compounds and D/A complex, respectively, are observed. Using optical absorption spectroscopy, we observe for each of the two mixed systems a set of new, strong transitions located in the near-IR range below the gap of the pristine compounds: such transitions are related to charge-transfer (CT) interactions between donor and acceptor. The optical anisotropy of domains of the D/A complexes with associated new electronic states is studied by ellipsometry. We infer that the CT-related transition dipole moment is perpendicular to the respective π-conjugated planes in the D/A complex

<i>V</i>_oc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells

The film morphology and device performance of planar heterojunction solar cells based on the molecular donor material α-sexithiophene (6T) are investigated. Planar heterojunctions of 6T with two different acceptor molecules, the C₆₀ fullerene and diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom layer has been varied between room temperature and 100 °C for each acceptor. By means of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular orientation of 6T is influenced by the preparation conditions and that the 6T film templates the growth of the subsequent acceptor layer. These structural changes are accompanied by changes in the characteristic parameters of the corresponding photovoltaic cells. This is most prominently observed as a shift of the open circuit voltage (<i>V</i>_oc): In the case of 6T/C₆₀ heterojunctions, <i>V</i>_oc decreases from 0.4 to 0.3 V, approximately, if the growth temperature of 6T is increased from room temperature to 100 °C. By contrast, <i>V</i>_oc increases from about 1.2 V to almost 1.4 V in the case of 6T/DIP solar cells under the same conditions. We attribute these changes upon substrate heating to increased recombination in the C₆₀ case while an orientation dependent intermolecular coupling seems to change the origin of the photovoltaic gap in the DIP case