Highly sensitive permeation measurements are crucial for the characterization and development of polymeric substrates for flexible display applications. In particular, organic light-emitting devices require substrates with extremely low permeation rates for water and oxygen. Here we demonstrate a concept for measuring ultralow permeation rates. The amount of oxidative degradation in a thin Ca sensor is monitored by in situ resistance measurements. The benefits of this technique are demonstrated for polyester foils with single- and double-sided barrier coatings. A sensitivity limit is imposed by the quality of the encapsulation. The resulting base line contribution to the water vapor transmission rate of a glass reference is below 10−6 g/m2 day at accelerated test conditions.

Organic light-emitting diodes were fabricated on a 125-μm-thick polyethylene terephthalate substrate covered with 100 nm indium tin oxide. The luminance–current–voltage performance and the emission spectrum of the devices are investigated in the bent state under mechanical stress at different bending radii. Down to a curvature of 15 mm, no significant decrease in the device performance is found compared to the relaxed state, as well as to conventional devices on glass substrates.

The active pixel concept is a promising architecture for imaging systems. We report on the electrooptical characterization of a hybrid organic active pixel sensor (APS) where an organic photodiode is integrated on top of an amorphous silicon thin-film transistor circuitry, which drives the image sensor and performs the signal processing. The active pixel approach provides an on-pixel amplification of the signal with a charge gain of up to 10. A fill factor that is close to 100% is obtained by embedding all transistors underneath the organic photodetector. We show that, as compared with organic passive pixels, the organic APS shows a higher sensitivity, making the detection of smaller signals possible.

Unrestricted geometry optimizations on [2.2]paracyclophane and cyclobutane at the MP2/6-31G(d) level led to significant ring distortions in agreement with experimental results. The MP2 method proved most successful in the study of the ring puckering of cyclobutane where various theoretical methods and basis sets were compared. Frequency calculations on [2.2]paracyclophane at the D 2 minimum and at the D 2 h saddle point demonstrate the influence of the molecular twist on the vibrational spectra. The two distorted minima are separated by a C 2 h symmetric barrier of 2.5 kJ/mol. Possible causes for the ring deformation in [2.2]paracyclophane are discussed.

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Accurate O–H⋯O hydrogen-bond dissociation energies were measured for the supersonic-jet-cooled complexes 1-naphthol⋅S with S=D2O, ethanol, oxirane, and oxetane. A mass-selective pump–dump–probe method was used, combining stimulated emission pumping with resonant two-photon ionization and ion-dip techniques. The ground-state dissociation energies D0(S0) are 5.83±0.13 kcal/mol for d1-1-naphthol⋅D2O, 7.94±0.02 kcal/mol for 1-naphthol⋅ethanol, 7.71±0.14 kcal/mol for 1-naphthol⋅oxirane and >8.17 kcal/mol for 1-naphthol⋅oxetane. The D0’s increase by 5%–7% upon excitation of 1-naphthol to the S1 state. These dissociation energies are compared to those of the analogous complexes with S=H2O, methanol, NH3, and ND3 [Chem. Phys. Lett. 246, 291 (1996)]. The trends in D0 are compared to the electric dipole moments μ, molecular polarizabilities ᾱ, and gas-phase proton affinities of the H bond acceptor molecules. For the O-containing acceptors, the D0’s correlate well with ᾱ, but the only good overall correlation for both O- and N-containing acceptors was found between the dissociation energies and proton affinities.

Hydrogen-bonded complexes of the photoacid 1-naphthol with NH3 and ND3 were investigated by resonant two-photon ionization, spectral hole burning, and fluorescence spectroscopies. Although the intermolecular vibrations are weak in both absorption and emission, with typical Franck–Condon factors <2% relative to the electronic origin, all six intermolecular modes were identified, namely the hydrogen bond stretch σ, the ammonia torsion τ, two in-plane wags β1 and β2, and two out-of-plane rocking motions ρ1 and ρ2. Several ammonia torsional excitations were observed, with spacings in good agreement with the S0- and S1 state effective torsional barriers derived by Humphrey and Pratt [J. Chem. Phys. 104, 8332 (1996)]. The β1, β2, and ρ2 vibrational excitations exhibit large (2–8 cm−1) torsional splittings, which indicate strong anharmonic coupling with the ammonia internal rotation. The observed Franck–Condon factors of the intermolecular stretching vibration imply a contraction of the O–H⋅⋅⋅N hydrogen bond by ≈0.01 Å upon S1←S0 excitation.

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