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  • 1
    Online Resource
    Online Resource
    Triplet Excitons in Crystals of Aromatic Molecules
    AIP Publishing ; 1965
    In:  The Journal of Chemical Physics Vol. 42, No. 1 ( 1965-01-01), p. 309-323
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 42, No. 1 ( 1965-01-01), p. 309-323
    Abstract: In the present paper we consider the band structure and the Davydov splitting of the first triplet exciton states in crystalline naphthalene, anthracene, and biphenyl. It is found that: (a) An important contribution to the triplet exciton bandwidth arises from intermolecular exchange interaction. These interactions are calculated in the molecular orbital π-electron approximation. (b) Excitation exchange effects due to spin—orbit coupling are negligible. (c) Nonorthogonality corrections, considered within the framework of the symmetric orthogonalization procedure, have been found to be small. (d) Crystal-field mixing of triplet states arising from π→π* excitations has no effect on the triplet bands. (e) An important contribution to the triplet exciton bandwidth may arise from configuration interaction with charge-transfer states. The dynamics of triplet excitons in aromatic crystals was studied in the two limiting cases of strong and weak scattering. The band model, with the constant mean-free-path approximation, leads to a mean free path of the order of one to two lattice distances and seems to be inappropriate. Triplet—triplet annihilation leading to delayed blue fluorescence in crystalline anthracene can be adequately described in terms of a random-walk diffusion model when the effects of charge-transfer interactions are included.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1695693
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1965
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 2
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    Organic thin film transistors using 6,13-bis(tri-isopropylsilylethynyl)pentacene embedded into polymer binders
    AIP Publishing ; 2009
    In:  Applied Physics Letters Vol. 94, No. 1 ( 2009-01-05)
    Details
    In: Applied Physics Letters, AIP Publishing, Vol. 94, No. 1 ( 2009-01-05)
    Abstract: The active channel material of an organic thin film transistor (OTFT), 6,13-bis(tri-isopropylsilylethynyl)pentacene (TIPS pentacene), is a functionalized pentacene designed to enhance both the solubility and solid-state packing of the pentacene. In this work, in order to improve device performance, three types of polymer binders—poly(α-methylstyrene) (PAMS), poly(4-vinylbiphenyl) (PVBP), and poly(triarylamine) (PTAA)—were employed to fabricate OTFT devices with organic soluble TIPS pentacene. These binders improved film formation in a large area uniformly and helped the TIPS pentacene to form a stronger binding between source/drain electrodes onto dielectric layer. Thus, device performance was highly improved due to improvement of interfacial contact and an increase in the charge transfer in the active channel. OTFTs using TIPS pentacene with PAMS, PVBP, and PTAA for field effect mobilities in the saturation regime have 5×10−3, 8×10−3, and 2.7×10−2 cm2/V s, respectively.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    URL: Article
    DOI: 10.1063/1.3063123
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2009
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 3
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    Determination of the Madelung potential of ionic crystals with a polar surface by the Ewald method
    AIP Publishing ; 1980
    In:  The Journal of Chemical Physics Vol. 72, No. 11 ( 1980-06-01), p. 6164-6168
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 72, No. 11 ( 1980-06-01), p. 6164-6168
    Abstract: Application of the Ewald method to the evaluation of the Madelung potential of a crystal slab possessing two-dimensional periodicity has been studied. The method involves a simple differential equation to be solved. When each crystallographic plane parallel to the surface contains equal amounts of opposite charges, the unique boundary condition leads to a unique solution and the correct Madelung potential in the surface region and the bulk. If the planes are not charge neutral, the boundary condition is ambiguous. A slab consisting of a dipoleless repeating unit layer satisfies a unique boundary condition. The method is applied to NaCl, CsCl, and β-alumina. A simple surface modification is shown to produce the slab bulk self-potential equal to the infinite crystal bulk self-potential.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.439074
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1980
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 4
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    On the ionic conduction in β-alumina: Potential energy curves and conduction mechanism
    AIP Publishing ; 1975
    In:  The Journal of Chemical Physics Vol. 63, No. 2 ( 1975-07-15), p. 772-778
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 63, No. 2 ( 1975-07-15), p. 772-778
    Abstract: Potential energy curves for various carrier ions in β-alumina have been calculated. All ions except the carrier ions (Li+, Na+, Ag+, K+, Rb+, Cs+) were assumed fixed in their equilibrium positions. These ionic positions were taken from Roth’s work. In our calculation the motion of carrier ions is restricted on lines of the two dimensional hexagonal network. We show that the site energy difference between the anti-Beevers–Ross site and the Beevers–Ross site is approximately 2 eV in stoichiometric crystals. In nonstoichiometric crystals the extra carrier ions may be paired to form interstitialcy pairs. The potential energy barriers for the in-phase motion of the interstitialcy pairs are found to be comparable to the experimental activation energies. Attempt frequencies have been calculated, and a simple random walk model is used for the electrical conductivities.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.431356
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1975
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 5
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    Exciton—Exciton Interactions and Photoconductivity in Crystalline Anthracene
    AIP Publishing ; 1963
    In:  The Journal of Chemical Physics Vol. 38, No. 2 ( 1963-01-15), p. 366-373
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 38, No. 2 ( 1963-01-15), p. 366-373
    Abstract: In this paper we consider the mechanism of photoconductivity in crystalline anthracene. It is shown that two excitons may interact to form a pair of charge carriers and an unexcited molecule. The computed rate of generation of charge carriers is 3.7×108 cm—3 sec—1, in satisfactory agreement with the (approximate) experimental value of 7.2×108 cm—3 sec—1 when the exciton concentration is 1.2×1010 cm—3. Other qualitative features of the proposed mechanism are in agreement with observation if electron-hole recombination is accounted for. Recent experiments by Silver demonstrating a photocurrent proportional to the square of the light intensity, and by McGlynn demonstrating the necessity for singlet states as the kinetic intermediate in charge-carrier generation are in agreement with the model proposed.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1733666
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1963
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 6
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    Exciton States and Optical Spectra in Linear Molecular Crystals
    AIP Publishing ; 1970
    In:  The Journal of Chemical Physics Vol. 52, No. 7 ( 1970-04-01), p. 3691-3702
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 52, No. 7 ( 1970-04-01), p. 3691-3702
    Abstract: Configuration interaction of many Frenkel exciton bands and charge-transfer states is carried out exactly. Based on the exact solution of the problem, the optical spectra is discussed. If the monomolecular optical transition is allowed, the intensities of exact exciton states are borrowed from the Frenkel excitons. Within the borrowed intensity approximation, resonance peaks and antiresonance dips in the continuum band are expected to appear depending on the magnitude of parameters. Although locations of resonances are independent of the orientation of the light polarization vector, positions and numbers of antiresonances do depend on it. Total number of antiresonances is at most one less than the number of Frenkel exciton bands. In the absence of resonance the continuum intensity depends very strongly on the nearest-neighbor charge pair interaction energy with larger intensity for smaller interaction energy. For the discrete spectra, the intensity is mainly distributed to the number of states equal to or one more than the number of Frenkel exciton bands. The relative intensities of these lines depend on the orientation of the light polarization vector. The intensity and position of the extra line varies with the nearest-neighbor charge pair interaction energy.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1673545
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1970
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 7
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    Optical Absorption by Charge-Transfer Excitons in Linear Molecular Crystals
    AIP Publishing ; 1969
    In:  The Journal of Chemical Physics Vol. 50, No. 4 ( 1969-02-15), p. 1524-1532
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 50, No. 4 ( 1969-02-15), p. 1524-1532
    Abstract: The optical absorption of linear molecular crystals is investigated theoretically. A generalization of the theory of excitons in linear molecular crystals was carried out by Merrifield who constructed the excited states of the crystal by mixing monomolecular states (Frenkel excitons) and bimolecular ionized states in which an electron is removed from one molecule in the crystal and placed on a second (charge-transfer states). If the monomolecular optical transition is allowed, we find that the optical absorption consists of a series of bound states and a continuum absorption, which gives rise to photoconductivity; the strength of all the absorption is predominantly borrowed from the Frenkel exciton. The experimental possibilities may be classified into three cases: (1) the Frenkel exciton, the charge-transfer state with electron and hole at nearest neighbors, and the state with the electron and hole at large separation are well separated in energy. This case gives rise to a strong absorption line, small charge-transfer sidebands, and very small absorption into the continuum. (2) Near resonance between Frenkel and nearest-neighbor charge-transfer states. The strong absorption is now shared by two absorption lines with weak sidebands and very small continuum absorption. (3) Resonance between the Frenkel state and the states with the electron and hole at large separation. This case corresponds to autoionization in a solid, the bound states have very weak absorption, and a strong sharp line will be observed within the continuum absorption. The width of the resonance line is directly proportional to the background absorption.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1671237
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1969
    detail.hit.zdb_id: 3113-6
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  • 8
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    Electrical Transport in Solids
    AIP Publishing ; 1983
    In:  Physics Today Vol. 36, No. 10 ( 1983-10-01), p. 90-90
    Details
    In: Physics Today, AIP Publishing, Vol. 36, No. 10 ( 1983-10-01), p. 90-90
    Type of Medium: Online Resource
    ISSN: 0031-9228 , 1945-0699
    URL: Article
    DOI: 10.1063/1.2915326
    RVK:
    UA 1000
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1983
    detail.hit.zdb_id: 2031187-4
    detail.hit.zdb_id: 208863-0
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  • 9
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    Charge-Transfer Exciton States in Aromatic Molecular Crystals
    AIP Publishing ; 1964
    In:  The Journal of Chemical Physics Vol. 41, No. 11 ( 1964-12-01), p. 3294-3306
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 41, No. 11 ( 1964-12-01), p. 3294-3306
    Abstract: In this paper we consider some of the consequences of the mixing of neutral exciton states (neutral excitation waves or Frenkel excitons) with charge-transfer exciton states (ion-pair excitons) in the oriented gas model of aromatic molecular crystals. The lowest-energy charge-transfer exciton is described by suitable symmetry-adapted functions built on the basis functions of a near-neighbor positive and negative ion pair. It is then shown that the energy of this state is not greatly different from the p states of anthracene and naphthalene, and therefore that the ion-pair exciton and Frenkel exciton states can mix. For the cases of anthracene and naphthalene, such configuration interaction leads to the following contributions to the Davydov splitting of the triplet manifold: Δε=26/ΔE cm−1naphthalene,Δε=31/ΔE cm−1anthracene,where ΔE is the energy difference (in electron volts) between the triplet level and the near-neighbor charge-transfer level. In making the computations, it is necessary to consider carefully the effects of vibronic coupling and of configuration changes in the excited state. It is concluded that charge-transfer excitons can make an important contribution to the Davydov splitting of a triplet manifold. This conclusion is supported by preliminary estimates of the interaction matrix elements for crystalline benzene.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1725728
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1964
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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  • 10
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    Electronic States of a Disordered Polymer
    AIP Publishing ; 1970
    In:  The Journal of Chemical Physics Vol. 53, No. 7 ( 1970-10-01), p. 2726-2735
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 53, No. 7 ( 1970-10-01), p. 2726-2735
    Abstract: A method introduced by Schmidt to give the vibrational frequency spectrum of an isotopic disordered one-dimensional lattice is generalized and applied to an infinite one-dimensional disordered molecular crystal with nearest-neighbor interactions. Such a model is applicable to a polymer having several molecular species arranged randomly along the polymer axis. Equations are derived which may be solved numerically to give the density of states for the following types of polymer: (1) the general disordered polymer having a random arrangement of several molecular species, the coupling constants between two species being determined by the species being coupled; (2) the glassy polymer having only one molecular species but with the coupling constants distributed randomly according to a continuous probability law. A numerical calculation of the density of states is made for the isotopic disordered polymer both with and without positional correlation between the molecular species and for the glassy polymer. When the energies of the two species in the diatomic isotopic disordered polymer differ by more than the nearest-neighbor coupling constant, the density of states is quite structured. Several of the peaks in this structure are associated with clusters of one or two molecules of one species in a lattice of molecules of the other species. Structure also appears in the density of states for the glassy polymer when there is a finite probability of small values for the nearest-neighbor coupling integrals.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.1674396
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1970
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
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