Highly Sensitive Absorption Measurements in Organic Thin Films: Charge Transfer Complexes and Light-Induced Changes

MRS Proceedings ◽

10.1557/proc-228-85 ◽

1991 ◽

Vol 228 ◽

Author(s):

Andrew Skumanich

Keyword(s):

Thin Films ◽

Charge Transfer ◽

Energy Levels ◽

Organic Thin Films ◽

Organic Films ◽

Charge Transfer Complexes ◽

Weak Charge ◽

Polymeric Thin Films ◽

Photothermal Deflection Spectroscopy ◽

Induced Changes

ABSTRACTUsing the sensitive absorption technique of Photothermal Deflection Spectroscopy (PI1S) it is possible to detect subtle spectral features in the absorption spectra of polymeric thin films that cannot be detected by other means. This paper describes observations of weak charge-transfer complex (CIC) formation and also light-induced changes in various organic films. The filns studied were those commonly used as charge transport materials in organic photoconductors, comprised of a small transport molecule and a polymer binder. The optically measured CTC bands can be used to establish single electron energy levels of the constituents. Reproducible photo-induced changes are manifest both in the strong UV transitions as well as in the “sub-gap” absorption and appear to be correlated with the photo-chemical stability of the constituents. The light-fatigue has both a reversible as well as irreversible component.

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Photoconductivity and magnetoconductance effects on vacuum vapor deposition films of weak charge-transfer complexes

Physical Chemistry Chemical Physics ◽

10.1039/c7cp02781h ◽

2017 ◽

Vol 19 (29) ◽

pp. 18845-18853 ◽

Cited By ~ 6

Author(s):

Ken Kato ◽

Shogo Hagi ◽

Masumi Hinoshita ◽

Eiji Shikoh ◽

Yoshio Teki

Keyword(s):

Thin Films ◽

Charge Transfer ◽

Vapor Deposition ◽

Pyromellitic Dianhydride ◽

Charge Transfer Complexes ◽

Weak Charge

Thin films of weak charge-transfer complexes (pyrene/dimethylpyromellidiimide or pyrene/pyromellitic dianhydride) were investigated by time-resolve ESR, photoconductivity, and magneto-photoconductance measurements.

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Vibrational Overtone Spectra in Polymeric Thin Films

MRS Proceedings ◽

10.1557/proc-228-91 ◽

1991 ◽

Vol 228 ◽

Author(s):

Andrew Skumanich ◽

Christopiier Moylan

Keyword(s):

Thin Films ◽

Wavelength Region ◽

Organic Thin Films ◽

Precise Determination ◽

Polymeric Thin Films ◽

Enhanced Sensitivity ◽

Photothermal Deflection Spectroscopy ◽

Vibrational Overtone ◽

Broad Energy Range ◽

Long Fibers

ABSTRACTWith the enhanced sensitivity of Photothermal Deflection Spectroscopy (PDS), vibrational overtone spectra have been obtained in organic thin films for the first time, covering the range from the near IR to the visible (0.4 - 2 eV). The absorption spectra of polycarbonate, for instance, exhibits C-I1 stretch modes for Δn> I where n is the vibrational quantum level. Previous measurements were constrained to either long fibers, which pose the problem of various scattering losses not related to absorption, or to a restricted wavelength region in the visible accessible by dye laser sources. The unparalleled sensitivity of PDS allows precise determination of frequency, lineshape and intensity of the various modes, even for films ∼10μm thick over a broad energy range. The overtone spectra can be used as a probe of various basic molecular properties. In a manner similar to NMR spectroscopy, it is possible to study specific atomic bonds.

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Raman studies of lattice vibrations in weak charge-transfer complexes: Naphthalene-tetrachlorophthalic anhydride

Chemical Physics Letters ◽

10.1016/0009-2614(84)85435-4 ◽

1984 ◽

Vol 109 (6) ◽

pp. 615-619 ◽

Cited By ~ 3

Author(s):

M.H. Kuok ◽

E.C. Looi ◽

S.H. Tang ◽

C.T. Lin ◽

C.A. Caetano

Keyword(s):

Charge Transfer ◽

Charge Transfer Complexes ◽

Lattice Vibrations ◽

Weak Charge

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Optoelectronic and Structural Properties of Vacuum-Deposited Crystalline Organic Thin Films

MRS Proceedings ◽

10.1557/proc-328-37 ◽

1993 ◽

Vol 328 ◽

Cited By ~ 4

Author(s):

S. R. Forrest ◽

P. E. Burrows ◽

E. I. Haskal ◽

Y. Zhang

Keyword(s):

Thin Films ◽

Quantum Wells ◽

Field Effect Transistors ◽

Organic Thin Films ◽

Potential Method ◽

Organic Films ◽

Light Emitting ◽

Organic Monolayer ◽

Molecular Beam Deposition ◽

Monolayer Growth

ABSTRACTRecently, it has been discovered that crystalline organic thin films can be deposited in nearly single crystalline form on a variety of substrates such as glass, polymers, etc. Since then, this discovery has led to the growth of crystalline organic quantum wells, waveguides, coupler/switches, and organic/ inorganic heterojunction devices such as field effect transistors and avalanche photodiodes. Organic light emitting diodes (LEDs) which luminesce in the red, green and blue have also been demonstrated. In this paper, we will report on several recent advances in the growth of organic thin films deposited by organic molecular beam deposition. We report on modeling of organic monolayer growth based on the atom-atom potential Method. The Model provides insight into the factors which control “quasi-epitaxial growth” i.e. the ordered growth of one layer of an organic film which is incommensurate with the substrate lattice. We also observe large optical nonlinearities which are a feature of both single and Multi-layer crystalline organic films. The growth of organic, nonlinear optically active crystalline organic compounds are also discussed.

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MOLECULAR MOTION IN WEAK CHARGE TRANSFER COMPLEXES

Canadian Journal of Chemistry ◽

10.1139/v66-138 ◽

1966 ◽

Vol 44 (8) ◽

pp. 945-952 ◽

Cited By ~ 15

Author(s):

D. F. R. Gilson ◽

C. A. McDowell

Keyword(s):

Nuclear Magnetic Resonance ◽

Charge Transfer ◽

Molecular Motion ◽

Charge Transfer Complexes ◽

Weak Charge ◽

Magnetic Resonance Studies ◽

Second Moments ◽

Line Nuclear Magnetic Resonance ◽

Pure Compounds ◽

Wide Line

"Wide line" nuclear magnetic resonance studies of several charge transfer complexes are reported. Line width transitions and comparisons of theoretical and experimental second moments indicate that molecular rotation occurs in several of these complexes. Estimates of the barriers to reorientation in the complexes show these to be lower than those observed for the corresponding pure compounds.

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