Özyeğin Üniversitesi, Çekmeköy Kampüsü Nişantepe Mahallesi Orman Sokak 34794 Çekmeköy İstanbul

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Ağu 05, 2019 - Ağu 10, 2019

Thesis Defense - Metehan Elibol (MSME)


Metehan Elibol - M.Sc. Mechanical Engineering

Prof. Mehmet Arık - Advisor




Date: 08.08.2019

Time: 11:00

Location: AB1 231




Thesis Committee: 

Prof. Mehmet Arık,  Özyeğin University

Asst. Prof. Polat Şendur,  Özyeğin University

Asst. Prof. Mete Budaklı, Turkish-German University



Flat-panel display technologies have been well developed over the last decade towards high-end products which have slimmer, higher brightness and wider color gamut (WCG) characteristics. These challenges led to a dramatic increase in power consumption and restricting mechanical design by affecting optical components and also limiting the volume for thermal design. At the present time, LED (light-emitting diodes) technology with some unique advantages such as long lifetime, high energy efficiency and high reliability is the most desirable solution to overcome the challenges in the high-end TV market. LED TV is a type of LCD (liquid crystal display) television and utilizes LEDs at the backlight in place of the conventional CCFLs (cold cathode fluorescent lights).

A number of phosphor concentrations have been proposed for advanced LED TV systems. The LEDs doped with KSF (K2SiF6:Mn4+) phosphor have made a rapid penetration to the high-end TV market as a solution to meet the requirement of the wider color gamut. However, the light output of the KSF LEDs is approximately 15% lower than conventional LEDs. Hence, high brightness expectation of the TV must be met by increasing the power consumption of the TV. Considering the thermal sensitivity of a typical KSF phosphor with high power consumption, the key point is to identify the thermal performance of optical and mechanical components with an optimal LED type to design a thermally and optically stable TV system.

This study focuses on investigating thermal and optical effects of the various LEDs doped with KSF in a 65” LED TV with computational thermal models and experimental studies.  The low inner volume and complex geometry of a TV pose crucial challenges to overcome that has been the main focus of this study. Modeling is initiated with geometry idealizations, and an analytical model (1D resistance network) is established to find out the total thermal resistance to obtain the least thermal resistance in the TV system. CFD (computational fluid dynamics) simulations with commercial software, Ansys Icepak, have been created to determine 3D heat transfer behavior. Furthermore, the LED junction temperature and the temperature distribution on the LCD surface are predicted with computational models. In the experimental study, the validation of thermal models is investigated with thermal measurements and the optical performances of the TV system for various LEDs are determined with optical measurements. Finally, the thermal and the optical performances of different LED chips are compared with each other.


Metehan Elibol obtained his Bachelor’s Degree from the Department of Physics Engineering at Hacettepe University. He enrolled master program of Mechanical Engineering at Ozyegin University. His research interests are the optical design of optomechanical systems and the thermal management of LED TVs. He specifically has the experience to design the optical part of backlight systems in LED LCD TVs. He currently works for Vestel Electronic Company as the optical system design architect.