Optical detection of deep electron traps in poly(p-phenylene vinylene) light-emitting diodes

The trap-limited electron currents in poly(p-phenylene vinylene) (PPV) derivatives can be modeled using a Gaussian trap distribution that is positioned approximately 0.75 eV below the lowest unoccupied molecular orbital (LUMO) of PPV. Photothermal deflection spectroscopy measurements and internal photo-emission spectroscopy measurements confirm...

Retention time and depolarization in organic nonvolatile memories based on ferroelectric semiconductor phase-separated blends

Resistive switches have been fabricated using a phase-separated blend film of ferroelectric random copolymer poly(vinylidene fluoride-co-trifluoroethylene) with the organic semiconductor regio-irregular poly(3-hexylthiophene) (rir-P3HT). Spin-coated blend films have been contacted with symmetrical Ag top and Ag bottom electrodes, yielding...

Charge transfer dynamics in polymer-fullerene blends for efficient solar cells

Blends of poly(3-hexylthiophene) (P3HT) and the bis-adduct of [6,61-pheuyl-C\61-butyric acid methyl ester (bisPCBM) show enhanced performances in bulk-heterojunction solar cells compared to P3HT:PCBM thin films due to their higher open-circuit voltage. However, it is not clear whether the decrease of the shortcircuit current observed in P3HT...

Electron trapping in higher adduct fullerene-based solar cells

Here, the performance of bulk-heterojunction solar cells based on a series of bisadduct analogues of commonly used derivatives of C60 and C 70, such PCBMs and theirthienyl versions, is investigated. Dueto their higher lowest unoccupied molecular orbital an increase in open-circuit voltage and thus performance is expected. It is shown that the...

Mechanistic study of excitation energy transfer in dye-doped PPV polymers

The mechanism of excitation energy transfer is studied using host-guest systems consisting of green and yellow emitting poly(phenylene vinylene) (PPV) based polymers into which red emitting dyes are dispersed. The photoluminescence from such polymer-dye systems is studied in the steady-state and time resolved. Furthermore, the...

Computer-modeling-based QSARs for analyzing experimental data on biotransformation and toxicity

Over the past decades the description of quantitative structure-activity relationships (QSARs) has been undertaken in order to find predictive models and/or mechanistic explanations for chemical as well as biological activities. This includes QSAR studies in toxicology. In an approach beyond the classical QSAR approaches, attempts have been made...