Electroluminescence of Polymer Nanocomposites

Mal’tsev, É. I.; Lypenko, D. A.; Bobinkin, Vladimir V.; Shapiro, B. I.; Тамеев, А. Р.; Wright, J.; Berendyaev, V. I.; Kotov, B. V.; Ванников, А. В.

doi:10.1080/10587250108025741

Cited by 6 publications

(4 citation statements)

References 8 publications

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“…From data on polarographic halfwave redox potentials of CD and from the energy gap (EG ¼ 1:49 eV) of the J-aggregates in the API layer, the HOMO (À5:36 eV) and LUMO (between À3:6 and À3:8 eV) energies were found elsewhere. 21) In the API, anthracene containing moiety is responsible for the transport of holes. 20) According to Vilesov et al, 25) the ionization potential of the anthracene molecular crystal is ranged between 5.0 and to 5.6 eV so the charge transfer between donor (i.e., anthracene moiety in the API) and acceptor (i.e., carbocyanine core in the J-aggregate) is plausible.…”

Section: Resultsmentioning

confidence: 99%

“…Thin films of the API/CD (9 wt %) composite (in which about one-half of the CDs forms J-aggregates) with the thickness ranged between 1 and 2 m were spin-cast from a chloroform solution. 21) The drift mobility of charge carriers was measured by a conventional time-of-flight (TOF) technique at room temperature. We described the experimental details elsewhere.…”

Section: Methodsmentioning

confidence: 99%

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Enhanced Charge Mobility in Polymer Nanocomposites Incorporating Donor–Acceptor Interfaces

Тамеев

Nikitenko

Ванников

2011

Jpn. J. Appl. Phys.

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Charge carrier transport in donor–acceptor (D–A) composites based on either poly(N-vinyl carbazole) or polyimide derivative incorporating either carbon single-walled nanotubes or nanocrystals of J-aggregated cyanine dyes is shown to exhibit a similar behavior. In the composite films, polymer/nanomaterial interface provides pathways of the high conductivity. Charge–transfer states (CTS) formed at the D–A interface are involved in the transport. The charge transport along the interface is suggested to arise due to the D–A integer charge transfer and strong interaction between adjacent opposite charges located on the donor and acceptor molecules. The approach based on the concept of sequence of charge carrier transfers through charge transfer states describes the increased electron and hole mobility in the composites. The approach predicts enhanced conductivity with reduced activation energy. Moreover, once the density of electron–hole pairs at the interface is rather high, significant part of the charge carriers can avoid hopping transport resulting in conductivity of metal type. The value of two-dimensional conductivity is estimated by numerical modeling.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Enhanced Charge Mobility in Polymer Nanocomposites Incorporating Donor–Acceptor Interfaces

Тамеев

Nikitenko

Ванников

2011

Jpn. J. Appl. Phys.

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“…3, curve for D=kT ¼ 5). In materials discussed in [2,4] D is large enough (D ' 0:5 eV), while preliminary experimental data indicate that formation of J-aggregates does not change mobility of holes in composite materials with small D [7].…”

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confidence: 99%

“…These so called J-aggregates [3] have spatially ordered structure and usually contain many molecules of a dye. Resulting composite polymeric materials demonstrate intense electroluminescence with narrow emission bands (attributed to J-aggregates) that could be exploited in electronic organic devices [2].There are reliable experimental indications that J-aggregates should serve as traps for electrons and holes, and yet hopping mobilities of both kinds of carriers are much greater (by order of magnitude or even more) in nanocomposite material in comparison with undoped polymer [2,4]; polymer matrices doped with non-aggregated dyes do not demonstrate increase in carrier mobility. This observation suggests that in relatively thin (with thickness l ' 100-200 nm) transport layers aggregates provide channels connecting the opposite electrodes so carriers could travel from one electrode to another without need to enter into the polymer matrix itself.…”

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confidence: 99%

Hopping transport of charge carriers in nanocomposite materials

Novikov

2003

phys. stat. sol. (c)

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Charge transport in polymers containing J-aggregates of cyanine dyes serving as fast transport channels is considered. Shape of photocurrent transient depends on initial spatial distribution of carriers. If carriers are homogeneously generated at the electrode surface, then at the initial stage current raises reflecting carrier collection to fast channels and corresponding rate constant is determined by channel density.1 Introduction Under certain conditions organic polymers (polyimides and others) doped with cyanine dyes demonstrate formation of nanosized dye aggregates in the bulk of the polymer matrix [1,2]. These so called J-aggregates [3] have spatially ordered structure and usually contain many molecules of a dye. Resulting composite polymeric materials demonstrate intense electroluminescence with narrow emission bands (attributed to J-aggregates) that could be exploited in electronic organic devices [2].There are reliable experimental indications that J-aggregates should serve as traps for electrons and holes, and yet hopping mobilities of both kinds of carriers are much greater (by order of magnitude or even more) in nanocomposite material in comparison with undoped polymer [2,4]; polymer matrices doped with non-aggregated dyes do not demonstrate increase in carrier mobility. This observation suggests that in relatively thin (with thickness l ' 100-200 nm) transport layers aggregates provide channels connecting the opposite electrodes so carriers could travel from one electrode to another without need to enter into the polymer matrix itself. Motion of carriers inside quasi-crystalline channels with reduced energetic disorder naturally explains higher mobilities of carriers in composite materials. Recently formation of sparse mesh of very long gently curved fibrils (with length 200-300 nm and longer) consisting of individual threads of J-aggregates with thickness of about 2.3 nm or, at larger concentration, of bundles of interwoven threads (with diameter about 10 nm) has been directly visualized in aqueous solutions of cyanine dyes [5]. Typical mesh scale is about 100 nm or greater.Thus, it seems that the simplest yet reasonable model of the composite material should be an isolated quasi-crystalline cylindrical channel with radius b that connects two electrodes and is surrounded by disordered polymer matrix. We used the lattice model of dipolar glass [6] to describe disordered polar polymer serving as a source of residual energetic disorder UðrÞ inside the channel. Sites of the channel carry no dipole moment and all energy fluctuations at these sites are due to contributions of the surrounding dipolar matrix (see Fig. 1). In the case of non-zero moment, aggregate's molecules still do not contribute to the energetic disorder and provide only spatially periodic addition to energy landscape. To model difference in positions of energy levels in the dipolar matrix and J-aggregate a constant value D was subtracted from the energy of every site inside the channel. Every basic cell

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