UScholar Works
 
Filters: Format: "application/pdf" Collection: "ir_uspace" Subject: "Excitons"
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CreatorTitleDescriptionSubjectDate
1 Mishchenko, EugeneCharge response function and a novel plasmon mode in graphenePolarizability of noninteracting 2D Dirac electrons has a 1 1 / √qv-ω singularity at the boundary of electron-hole excitations. The screening of this singularity by long-range electron-electron interactions is usually treated within the random phase approximation. The latter is exact only in the ...Excitons; Random phase approximation2008-04
2 Lupton, John MarkEfficient dipole-dipole coupling of Mott-Wannier and Frenkel excitons in (Ga,In)N quantum well/polyfluorene semiconductor heterostructuresWe investigate interactions between Mott-Wannier (MW) and Frenkel excitons in a family of hybrid structures consisting of thin organic (polyfluorene) films placed in close proximity (systematically adjusted by GaN cap layer thickness) to single inorganic [(Ga, In)N/GaN] quantum wells (QWs). Charac...Mott-Wannier; Frenkel; Excitons; Dipole-dipole coupling; Semiconductor heterostructures2007-07
3 Vardeny, Zeev ValentineExcitons, polarons, and laser action in poly(p-phenylene vinylene) filmsWe have used a multitude of linear and nonlinear cw optical spectroscopies to study the optical properties of water precursor poly(p-phenylene vinylene) (PPV) thin films. These spectroscopies include absorption, photoluminescence, photoinduced absorption and their respective optically detected magne...PPV films; Excitons; Laser action; Poly(p-phenylene vinylene)2003
4 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Illumination-induced metastable polaron-supporting state in poly(p-phenylene vinylene) filmsWe found an illumination-induced metastable polaron-supporting state in films of a soluble derivative of poly-p-phenylene vinylene (MEH-PPV). Pristine, nonilluminated MEH-PPV polymer films do not show longlived photogenerated polarons. Prolonged UV illumination, however, is found to induce a revers...Metastable polaron-supporting state; Poly(p-phenylene vinylene); PPV; MEH-PPV; Excitons2007-07
5 Vardeny, Zeev ValentineLaser action in conducting polymersWe discuss both cooperative radiation and stimulated emission and consider their role in spectral narrowing of luminescent conducting polymers. We argue that cooperative radiation is favored in films with poor optical confinement. On the other hand, directional stimulated emission can be observed in...Laser action; Cooperative radiation; Stimulated emission; PPV; Disubstituted polyacetylene; Excitons; Spectral narrowing; Plastic lasers; Superfluorescence; Microcavity lasers1997
6 Vardeny, Zeev ValentinePhotophysics of excitons in quasi-one-dimensional organic semiconductors: single-walled carbon nanotubes and ∏-conjugated polymersThe nature of the primary photoexcitations in semiconducting single-walled carbon nanotubes (S-SWCNTs) is of strong current interest. We have studied the emission spectra of S-SWCNTs and two different rr-conjugated polymers in solutions and films, and have also performed ultrafast pump-probe spectro...Photophysics; Excitons; Quasi-one-dimensional; Single-walled carbon nanotubes; pi-conjugated polymers2006-02
7 Lupton, John MarkRecombination kinetics in wide gap electroluminescent conjugated polymers with on-chain emissive defectsWe analyze the experimental dependence of temporally and spectrally resolved electroluminescence (EL) from polyfluorene-based light-emitting diodes on electric field and temperature. The blue band in the EL spectrum is caused by emission from the polymer backbone, while the low-energy green emission...Recombination kinetics; On-chain emissive defects; Wide gap; Blue-emitting; Green-emitting; Excitons2003
8 Vardeny, Zeev ValentineTransient spectroscopy of Frenkel and charge transfer excitons in α-sexithienyl filmsPhotoexcitations dynamics are investigated in a-sexithienyl nanocrystalline films using transient photomodulation in a spectral range from 0.4 to 2.5 eV and time domain from 200 fs to 50 ms. We identify intrachain and interchain excitations. The former are even parity excitons with ultrafast dynami...Transient spectroscopy; Excitons; Frenkel exciton; Charge transfer exciton; Transient photomodulation1997-10
9 Vardeny, Zeev ValentineUltrafast dynamics of excitons and solitons in disubstituted polyacetyleneWe studied the ultrafast photoexcitation dynamics in disubstituted polyacetylene (DPA). We found two distinctively different relaxation channels for the photogenerated excitons; ionic and covalent pathways. In DPA films the photogenerated odd-parity (Bu) excitons that are responsible for the high ...Ultrafast dynamics; Photoexcitation; Excitons; Disubstituted polyacetylene; Excitons; DPA; Relaxation channels2003-01
10 Vardeny, Zeev ValentineUltrafast spectroscopy of excitons in single-walled carbon nanotubesWe studied the femtosecond dynamics of photoexcitations in films containing semiconducting and metallic single-walled carbon nanotubes (SWNTs), using various pump-probe wavelengths and intensities.We found that confined excitons and charge carriers with subpicosecond dynamics dominate the ultrafas...Ultrafast spectroscopy; Excitons; Single-walled carbon nanotubes; SWNT2004-01
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