Correlation between Dispersivity of Charge Transport and Holographic Response Time in an Organic Photorefractive Glass

Hofmann, Uwe; Grasruck, M.; Leopold, André; Schreiber, Andreas; Schloter, Stefan; Hohle, Christoph; Strohriegl, Peter; Haarer, and D.; Zilker, Stephan J.

doi:10.1021/jp9935283

Cited by 31 publications

(24 citation statements)

References 22 publications

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“…The response time, initially 30 ms, [64] can be pushed down to 2.5 ms with the use of an optimized plasticizer and a high Dn of 6 Â 10 À3 was obtained. [65,66] Furthermore, shelf lifetimes of nearly two years have been reported. [65] Thus, low molecular weight glasses show promise for further development; nevertheless, systematic variations of the chromophore and the photoconductor require extensive synthetic efforts.…”

Section: Low Molecular Mass Glassesmentioning

confidence: 99%

“…Performance characteristics of organic photorefractive materials in terms of holographic speed t À1 and optical gain G at a power density of 1 W cm À2 . The systems are the amorphous glass DR1-DCTA [65] and the fastest liquid crystal reported so far. [77] The host ± guest systems depicted are PVK composites with the chromophores AODCST, [55] DMNPAA, [48] FTCN, [36] and PDCST, [37] a polyfluorene (TFB), [32] and TPDac.…”

Section: Qualitative Comparisonsmentioning

confidence: 99%

“…[65] Whereas the mobility barely changed, the plasticizer EHMPA strongly increased the degree of dispersivity, meaning that it increased D 0 .…”

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confidence: 99%

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Materials Design and Physics of Organic Photorefractive Systems

Zilker¹

2000

ChemPhysChem

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Section: Low Molecular Mass Glassesmentioning

confidence: 99%

Section: Qualitative Comparisonsmentioning

confidence: 99%

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Materials Design and Physics of Organic Photorefractive Systems

Zilker¹

2000

ChemPhysChem

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“…Zilker and co-workers have also shown that a more dispersive charge transport leads to a slower holographic response. 26 The doping of B6 with ferrocene also results in a decrease in steady-state amplitude of the diffracted beam. This evolution is shown in Fig.…”

Section: Photorefractive Propertiesmentioning

confidence: 99%

Effect of the chromophore donor group and ferrocene doping on the dynamic range, gain, and phase shift in photorefractive polymers

Hendrickx

Steenwinckel

Persoons

et al. 2000

The Journal of Chemical Physics

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Diffraction efficiency and phase stability of poly (N-vinylcarbazole) -based photorefractive polymer composites as a function of azo-dye concentrationWe have studied the photorefractive performance of poly͑N-vinylcarbazole͒-based composites doped with various concentrations of two structurally related dipolar chromophores, at 780 nm. The two chromophores had different electron donor groups, N,N-diethylamine and julolidine, respectively. Complete internal diffraction and gain coefficients Ͼ130 cm Ϫ1 were obtained for polymers doped with these chromophores. The polymers prepared with the chromophore having the strongest electron donor group, the julolidine group, had the largest dynamic range, but proved to be slower and had a smaller photorefractive phase shift.

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“…Additional HTOF investigations in an organic glass were performed in Ref. [37]. As mentioned above, for dispersive charge transport the relationship between the drift velocity measured by the time delay of the first peak in a non-oscillating HTOF trace and the actual distribution of mobilities is not a-priori clear.…”

Section: Review Of Mobility Investigations Performed Using Htofmentioning

confidence: 99%

Holographic Time of Flight

Biaggio

Photo-Excited Processes, Diagnostics and Applications

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The Holographic Time of Flight (HTOF) method for the all-optical, contact-less investigation of charge transport in non-centrosymmetric insulators and semiconductors is based on the instantaneous photoexcitation of a spatially modulated distribution of charge carriers and on the linear electro-optic (Pockels) effect to visualize a charge-displacement by its associated refractive index change. It can be used with a free-carrier density so low that it does not otherwise have any detectable influence on the optical properties of a material, and with short free carrier lifetimes of the order of nanoseconds or less. HTOF is an especially striking example of how several independent linear and nonlinear light-matter interaction mechanisms can join to deliver a peculiar wave-mixing effect that is directly determined by a seemingly unrelated microscopic parameter: the free-carrier mobility. This chapter reviews the HTOF method and provides a detailed theoretical treatment that will be invaluable to experimentalists interested in applying this method to new materials. The author discusses the experimental parameters that influence the HTOF results and presents the basic assumptions and experimental conditions that allow the characterization of charge transport in the bulk of a material, with a sub-nanosecond time resolution only limited by the duration of the laser pulses, and for transport lengths down to a fraction of a micrometer. IntroductionBy illuminating a dielectric material with a pulsed laser it is possible to optically excite free electrons or holes, either from donor centers in the energy band gap between valence and conduction band, or directly by interband transitions. This leads to a transient increase in the number of free charge carriers, and therefore of the conductivity. Transient studies of current initiated by optical excitation of charge carriers lead to several ways to study charge transport processes in insulators and semiconductors.Homogenous charge-carrier photoexcitation in the bulk of a sample can be achieved by photoionization of impurity centers with energy levels inside the energy band gap. The analysis of such a homogenous photoconductivity transient gives some information on the charge transport properties, but generally delivers only indirect information on the charge-carrier mobility.On the other hand, the optical excitation of a packet of charges localized at the surface of a sample, either by interband excitation or by charge-carrier injection, is at the basis of conceptually simple methods to measure drift mobilities [1]. These methods rely on the observation of the drift of a charge-carrier packet in an applied electric field by its controlled photoexcitation and the detection of its time-of-arrival after a well-defined transport length. A well-established tool to CHAPTER 4

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Correlation between Dispersivity of Charge Transport and Holographic Response Time in an Organic Photorefractive Glass

Cited by 31 publications

References 22 publications

Materials Design and Physics of Organic Photorefractive Systems

Materials Design and Physics of Organic Photorefractive Systems

Effect of the chromophore donor group and ferrocene doping on the dynamic range, gain, and phase shift in photorefractive polymers

Holographic Time of Flight

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