Electrophotography

Weiss, David S.; and, J. Robin Cowdery; Young, Ralph H.

doi:10.1002/9783527618248.ch73

Cited by 13 publications

(8 citation statements)

References 345 publications

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“…The absence of a long lasting tail in the stimulated emission indicates that only adsorbed sensitizer molecules undergoing efficient electron injection are probed and that free dye anions in solution have only a negligible contribution. The dynamics measured on ZrO 2 shows clearly that two reactions with very different rates take place from the singlet excited state of the dye: An ultrafast process with dynamics similar to what was observed on TiO 2 , and a slower one which resembles the natural decay of the singlet state. The solid lines on the graphs represent polyexponential fits of the experimental data.…”

Section: Resultsmentioning

confidence: 61%

“…Light-induced electron injection from molecular dyes into the conduction band of wide-band gap semiconductor nanoparticles is currently intensely studied. This process is at the base of numerous technical applications, such as silver photography, xerography, and molecular photovoltaics, , which rely on the redox sensitization of semiconducting materials. From a fundamental standpoint, electron transfer from the excited state of a donor molecule to a continuum of electronic acceptor states in a solid also has significant importance.…”

Section: Introductionmentioning

confidence: 99%

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Femtosecond Dynamics of Interfacial and Intermolecular Electron Transfer at Eosin-Sensitized Metal Oxide Nanoparticles

2003

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Photoinduced electron injection from eosin Y into the conduction band of titanium dioxide was further scrutinized, as previous studies on the charge injection from xanthene dyes have led to diverging conclusions. Eosin-sensitized TiO 2 constitutes in many aspects a model system for studying the dynamics of charge injection: Adsorption of the sensitizer onto the oxide surface through electrostatic interaction and hydrogen bonding make this system exemplary of the weak electronic coupling case. The formation of dimeric eosin on the surface of metal oxide nanoparticles in an aqueous suspension was inferred from the study of the deactivation of the dye's singlet excited state on insulating particles, such as ZrO 2 and Al 2 O 3 , and of the formation of the resulting radical ion pair, using femtosecond stimulated emission and transient absorption. It was found that dimers undergo ultrafast dismutation with a time constant of 500 fs. The same process occurs also on TiO 2 particles and results in a competition between interfacial and intermolecular electron transfer. Two time constants of 160 fs (58%) and 1 ps were obtained for the charge injection from the singlet excited state of eosin into this semiconductor. The presence of poly(vinyl alcohol), often used as a stabilizer for aqueous colloidal suspensions, was observed to prevent the dimer formation on the surface but also to slow the rate of electron injection by orders of magnitude. This observation is rationalized in terms of an increased distance between the semiconductor surface and the chromophore because of the adsorption of polymeric chains onto the particles and a decrease of the electronic coupling matrix element associated to the charge transfer process. These findings remove the apparent discrepancies perceived between early measurements and more recent reports and highlight the role played by the mode of adsorption of the sensitizer in controlling electron injection kinetics.

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Section: Resultsmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Femtosecond Dynamics of Interfacial and Intermolecular Electron Transfer at Eosin-Sensitized Metal Oxide Nanoparticles

2003

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“…Triarylamines are important hole-conducting materials for optoelectronic devices, most importantly for OLEDs but also for electrophotography. − The donor strength can easily be tuned by substituents in ortho - and para -positions whose presence is also a prerequisite for making triarylamine radical cations chemically stable as these tend to dimerize at the otherwise unblocked para -position. , Furthermore, the relatively small reorganization energy of the triarylamines supports fast electron-transfer processes.…”

Section: Introductionmentioning

confidence: 99%

Charge-Transfer Interactions in a Multichromophoric Hexaarylbenzene Containing Pyrene and Triarylamines

Lambert¹,

Ehbets²,

Rausch³

et al. 2012

J. Org. Chem.

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Two different hexaarylbenzenes with three pyrene and three triarylamine substituents in different positions (trigonal symmetric and asymmetric arrangement) were synthesized, and their charge-transfer states were investigated by optical spectroscopy. In these multichromophoric systems triarylamine acts as the electron donor and pyrene as the electron acceptor. A reference chromophore with only one donor-acceptor pair was also investigated. All these chromophores form charge-transfer states upon photoexcitation which relax with a moderate fluorescence quantum yield to the ground state. The compounds do not differ significantly concerning most of their fluorescence properties, which shows that the fluorescent charge-transfer state is very similar in all chromophores. This observation indicates symmetry breaking for the symmetric chromophore within fluorescence lifetime of several tens of ns. This interpretation was substantiated by fluorescence excitation anisotropy measurements in a sucrose octaacetate matrix.

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“…Organic MV systems with triarylamine redox centers are the focus of many studies − because of their close relationship to the triarylamine systems that are widely used as hole conductive layers in (opto)electronic devices such as organic light-emitting diodes, field-effect transistors, or solar cells. − In these devices, the dynamics of intermolecular hole transfer play a crucial role, and tuning this process is of the utmost importance for device optimization. While many studies of charge carrier mobility in triarylamine-based solid state materials are available, almost nothing is known about the rates of the elementary hole transfer step between two adjacent triarylamine groups.…”

Section: Introductionmentioning

confidence: 99%

Electron Paramagnetic Resonance Spectroscopy of Bis(triarylamine) Paracyclophanes as Model Compounds for the Intermolecular Charge-Transfer in Solid State Materials for Optoelectronic Applications

et al. 2009

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A set of seven bis(triarylamine) mixed-valence radical cations with different bridging moieties were investigated by temperature-dependent electron paramagnetic resonance (EPR) spectroscopy in methylene chloride and ortho-dichlorobenzene to evaluate the thermal electron transfer rate constants. The bridges used comprise [2,2]paracyclophane and [3,3]paracyclophane as well as fully conjugated phenylene spacers. The cyclophanes serve as model structures for studying the intermolecular electron transfer in solid state materials. The activation barriers derived by EPR measurements are compared with those estimated by the two-state Marcus-Hush analysis as well as by its extension to three states. Both methods gave good agreement with the EPR data, the three-state method being slightly better than the two-state method. On the basis of the choice of the different bridging groups, our study shows that the bridge can have a significant influence on the internal reorganization energy. [2,2]Paracyclophane and [3,3]paracyclophane bridge units show practically the same electronic coupling and thermal barrier. Conjugated bridges have thermal rates about 1 order of magnitude larger than the radical cations with broken conjugation. These two aspects show that in solid state materials triarylamines drawn close to their van der Waals radii may exhibit efficient coupling and rate constants by only 1 order of magnitude smaller than fully conjugated materials.

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Electrophotography

Cited by 13 publications

References 345 publications

Femtosecond Dynamics of Interfacial and Intermolecular Electron Transfer at Eosin-Sensitized Metal Oxide Nanoparticles

Femtosecond Dynamics of Interfacial and Intermolecular Electron Transfer at Eosin-Sensitized Metal Oxide Nanoparticles

Charge-Transfer Interactions in a Multichromophoric Hexaarylbenzene Containing Pyrene and Triarylamines

Electron Paramagnetic Resonance Spectroscopy of Bis(triarylamine) Paracyclophanes as Model Compounds for the Intermolecular Charge-Transfer in Solid State Materials for Optoelectronic Applications

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