Sharif, Parisa
This thesis presents a novel method for fabrication of OLEDs on a specific flexible PET substrate with graphene anodes, demonstrating low sheet resistance, high work function, and an extremely high luminance. Firstly, a single-layer graphene growth process with chemical vapor deposition (CVD) method is optimized. Flexible anodes are then fabricated by stacking 7-layers of graphene films and doped with nitric acid to reduce the sheet resistance. Modified few layer graphene anodes by 29 Ω/□ sheet resistance and 84% transparency are used to fabricate OLEDs with a new family of thermally activated delayed fluorescence (TADF) materials. Observation of TADF in conjugated systems redefined the molecular design approach to realize highly efficient OLEDs in the early 2010s. Enabling effective reverse intersystem crossing (RISC) by minimizing the difference between singlet and triplet excited state energies (ΔEST) has been proven to be a widely applicable and fruitful approach, which resulted in the unproduction of numerous OLED devices with remarkable external quantum efficiencies (EQE). Here, a new series of TADF materials (SeTADFs) with heavy-atom selenium is used as emitters in OLED structure. One of these materials, SeDF-B, resulted in pure blue emission with EQEs approaching 26%. Additionally, flexible graphene-based electrodes were developed for OLEDs vi and revealed similar performance with indium tin oxide (ITO) on glass in most cases while, remarkably, suppressing ITO/Glass in pure blue OLED devices. These devices highlight the first-ever TADF based OLEDs that utilize graphene-based anodes in the literature.


Magnetic Properties and Cation Distribution of Bimetallic (Mn-Co) Doped NiFe2O4 Nanoparticles
Baykala, A.; Eryiğit, Sümeyra; Amir, Md; GÜNGÜNEŞ, HAKAN; Sozeri, H.; Shirsath, Sagar E.; Sertkol, M.; Asiri, Sarah M. (2017-11-01)
Nickel ferrite (NiFe2O4), an inverse spinel crystal structure and a soft transition metal oxide, contemplated as a good magnetic semiconducting material with low coercivity and saturation magnetization (M (s)). In this study, Ni1-2xMnxCoxFe2O4 (0.0 <= x <= 0.5) nanoparticles were synthesized by the microwave assisted approach with citric acid as fuel. The effect of both cobalt and manganese substitution on the morphological, structural, and magnetic properties of the NiFe2O4 nanoparticles were studied. X-ra...
Accuracy of the Surface Integral-equation Formulations for Large Negative Permittivity Values
Karaosmanoglu, B.; Ergül, Özgür Salih (2017-05-25)
Computational solutions of plasmonic problems involving metals at optical frequencies formulated with surface integral equations are considered. Numerical inaccuracies arise when using the conventional formulations for penetrable bodies, especially as the negative real permittivity becomes very large at the lower frequencies of the optical spectrum. In order to close the gap between plasmonic and perfectly conducting simulations, it is required to extend the applicability of surface integral equations to in...
Comparison of conventional and collapsed region operation of capacitive micromachined ultrasonic transducers
Huang, Yongli; Haeggstrom, Edward; Bayram, Barış; Zhuang, Xuefeng; Ergun, Arif Sanh; Cheng, Ching-Hsiang; Khuri-Yakub, Butrus T. (2006-10-01)
We report experimental results from a comparative study on collapsed region and conventional region operation of capacitive micromachined ultrasonic transducers (CMUTs) fabricated with a wafer bonding technique. Using ultrasonic pulse-echo and pitch-catch measurements, we characterized single elements of 1-D CMUT arrays operating in oil. The experimental results from this study agreed with the simulation results: a CMUT operating in the collapsed region produced a higher maximum output pressure than a CMUT ...
Experimental investigation of effects of cutting parameters on surface roughness in the WEDM process
Gökler, Mustafa İlhan (2000-10-01)
The experimental study presented in this paper aims to select the most suitable cutting and offset parameter combination for the wire electrical discharge machining process in order to get the desired surface roughness value for the machined workpieces. A series of experiments have been performed on 1040 steel material of thicknesses 30, 60 and 80 mm, and on 2379 and 2738 steel materials of thicknesses 30 and 60 mm. The test specimens have been cut by using different cutting and offset parameter combination...
Nonlinear optical properties of low temperature annealed silicon-rich oxide and silicon-rich nitride materials for silicon photonics
Minissale, S.; Yerci, Selçuk; Dal Negro, L. (2012-01-09)
We investigate the nonlinear optical properties of Si-rich silicon oxide (SRO) and Si-rich silicon nitride (SRN) samples as a function of silicon content, annealing temperature, and excitation wavelength. Using the Z-scan technique, we measure the non-linear refractive index n(2) and the nonlinear absorption coefficient beta for a large number of samples fabricated by reactive co-sputtering. Moreover, we characterize the nonlinear optical parameters of SRN in the broad spectral region 1100-1500 nm and show ...
Citation Formats
P. Sharif, “TRANSPARENT GRAPHENE ANODES FOR ORGANIC LIGHT EMITTING DIODES,” Ph.D. - Doctoral Program, Middle East Technical University, 2021.