Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Fabrication and Characterization of Perylene Diimide Doped Polyfluorene Based Solution Processed Blue Organic Light Emitting Diodes(2023) Varlıklı, Canan; Utlu, Sevde Nur; Demir, Mustafa Muammer; Varlıklı, Canan; Demir, Mustafa MuammerBlue is considered as the major component in many applications of organic light emitting diodes (OLEDs). Most of the polymeric blue emitters including poli[9,9-di-(2-diethylhexyl)-fluorenyl-2,7-diyl] (ADS231BE) attract attention with their solubility and potential in reducing the application costs, but also suffer from wide electroluminescence resulting in color purity issues. Annealing temperature and solvent choice have great influence on morphology and electronic properties. A typical OLED is fabricated by using ADS231BE as the emitter material and effect of annealing temperature on EL properties is investigated between 60C and 150C. OLEDs produced using toluene have shown better efficiency compared to those using chlorobenzene. Regardless of the solvent used, the efficiencies gradually decreased, but the stability and color purity of the devices increased with increasing annealing temperatures. Surface morphologies were examined, and suitable coating conditions were determined. Small molecule orange-red-emitting N,N'-bis(2-ethylhexyl)perylene-3,4,9,10-dicarboxylic diimide (PDI) derivatives were introduced into the blue-emitting conjugated polymer ADS231BE at a concentration of 0.1 wt.%. Electroluminescence, morphology, photoluminescence and Raman analysis of the developed devices were completed to determine the type of aggregation and conformational change caused by PDI doping. Subsequently, to balance charge and improve the electroluminescent character of the devices, a hole transfer layer (HTL) consisting of Poly (N-vinyl carbazole) (PVK) and PVK:1,3-Bis(N-carbazolyl) benzene (mCP) was added to the device structure. Similar morphological and Raman analyses were performed. Compared to the bare ADS231BE containing devices, without changing the CIE coordinate values, approximately, 10 folds of luminance and more than 5 folds of EQE increments were obtained.Master Thesis Development of Nanopatterns on Self Assembled Monolayer (sam) Organic Films Using Scanning Probe Microscope (spm) Nanolithography Techique(Izmir Institute of Technology, 2006) Gül, Semra; Okur, SalihPatterning and fabrication of nanostructures on surfaces is a great demand for nanoscale electronic and mechanical devices. Current techniques such as electron beam lithography and photolithography provides limited resolution and they are not capable of reproducible in nanoscale. Among those, Scanning Probe Microscopy (SPM) lithography that uses a nanometer sharpened tip has demonstrated outstanding capabilities for nanometer level patterning on various surfaces. Moreover, SPM techniques offer creating nanopatterns of Self Assembled Monolayers (SAMs) with molecular precision and visualizing surfaces with the highest spatial resolution. In this work, nanoscratches on gold surfaces and oxidation patterns on titanium surface were successfully performed as example of SPM lithography. In the second stage, Octadecylamine-HCl, Octadecanetiol (ODT) and Decylmercaptan (DM) SAM organic films were fabricated on various substrates; i.e., mica, silica, titanium surface deposited on silicon, n and p type silicon, using self assembly film preparation techniques. The film thicknesses were measured with Atomic Force Microscope (AFM). Nanopatterns were fabricated on SAM films using AFM tip by exerting a local high pressure at the contact that causes the displacement of SAM molecules by a high shear force. It was observed that there was no formation of SAMs on n type Si and silica substrates whereas there were organic assemblies on the other substrates. Fabricated nanopatterns were examined and thickness measurement was done. Molecular lengths of the organics were evaluated by using of SPARTAM 02 LINUX-UNIX with the method of PM3 and the measured values were compared with the calculated ones and it was concluded that monolayers were formed on the surfaces.Master Thesis Application of Self Assembled Monolayer Technique To Imporove Hole Transport in Organic Leds(Izmir Institute of Technology, 2011) Şeker, Mavişe; Okur, SalihThis thesis concentrates on the fabrication and characterization of highly efficient Organic Light-Emitting Diode (OLED) with surface modification of indium tin oxide (ITO) anodes by using self-assembled monolayer (SAM) technique. ITO has beencommonly used as an anode for OLEDs, because of the combination of high optical transparency and good electrical conductivity. That is why, ITO substrate is used in this study. On the other hand, the ITO film has often a rough surface, relatively low work function compared with the adjacent organic layer and its surface energy is not well matched to nonpolar organic film. For this purpose, in this work, eleven different SAM molecules were examined to modify ITO surface. Clearly, we aim to reduce the barrier of hole injection, lower the turn-on voltage and improve charge transfer characteristic at the anode-organic film interface using SAM molecules.The ITO work function with the SAM molecules was measured using Kelvin Probe Force Microscopy (KPFM). KPFM measurements were carried out to investigate if there is any increase in ITO work function. Atomic Force Microscopy (AFM) via semi-contact mode was examined the surface morphology of modified ITO. The transmittances of the ITOs with SAM were measured using an UV spectrometer. In addition to these surface analyses, the device performances were characterized by Keithley 236 and High-Resolution Spectrometer. Moreover, Space-Charge-Limited Current (SCLC) and Schottky models were used to analyze the I-V characteristics to calculate hole mobility and barrier heights, respectively.