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Title
Investigation of Organic Thin Films for Application in
Electro-Optic Devices
Author
JOBANPUTRA, MANISH C
Degree
MS, University of Cincinnati, Engineering : Materials Science ,
2002.
Abstract
Conjugated poly(p-phenylene vinylene) (PPV) is one of the most
promising organic materials for electro-optic devices. The optimum thermal
elimination conditions to get fully converted PPV from the precursor route was
sought. The degree of conversion to PPV was determined using IR measurements,
which showed 92% conversion in the temperature range studied (100 - 225 ºC). A
large difference was observed in the photoluminescence (PL) efficiency
depending on the conversion conditions. Different spectroscopic methods,
includes UV-Vis, PL, FT-IR, were used for detailed investigation of this
elimination reaction. It enabled us to optimize the conversion conditions and
obtain fully converted PPV films with high PL efficiencies. It was found that
the precursor films should be heated to 200 ºC and kept at this temperature for
2 hrs. under vacuum to get the fully converted PPV films. The design and
fabrication of low-drive-voltage organic LEDs was also carried out and results
of the three-layer LED based on PVK-PPV-PANI systems are presented. Fully
converted PPV was used as an exciton confinement layer in this device. Such a
device requiring a very low drive voltage is very useful in the electro-optics
and related industries and has many potential applications. In most of the
electro-optic device applications the main fabrication problem is to get
uniform, defect-free and reproducible thin films of these materials. In this
investigation, a RF plasma reactor was used to produce cross-linked organic
thin films from different organic precursors, which included benzene, furan,
aniline and toluene. Uniform thin films of desired thickness were fabricated
using this plasma polymerization technique. The composition of the
plasma-polymerized films were determined using X-ray photoelectron spectroscopy
(XPS). FT-IR spectra of the monomers and plasma polymerized thin films prepared
were compared in order to analyze the chemical structure of the films. UV-VIS
absorption spectroscopy of these films shows the amount of conjugation present
in the films. PL spectra of the films show that these materials can be used
into electro-optic device applications. In particular PP benzene showed maximum
PL emission at 460 nm, PP furan at 445 nm and PP toluene at 487 nm with a
shoulder at 410 nm.
Keywords
plasma polymerization; LED'S; photoluminescence; organic thin
films; opto-electronics