INVESTIGATION OF ORGANIC THIN FILMS FOR APPLICATION IN ELECTRO-OPTIC DEVICES
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.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:plasma polymerization led s photoluminescence organic thin films opto electronics
Date of Publication:01/01/2002