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Title:Spectrum management for high efficiency photonic devices
Author(s):Cifci, Osman Safa
Director of Research:Braun, Paul V.
Doctoral Committee Chair(s):Braun, Paul V.
Doctoral Committee Member(s):Shim, Moonsub; Chen, Qian; Toussaint, Kimani C.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Spectrum management
Abstract:Spectrum management holds great promise for high-performance photonics devices. Optical elements that split, up- or down-convert the available light to a specified spectrum can result in higher efficiencies in various devices such as photovoltaic cells, photodetectors, and electronic displays. In this thesis, the method of spectrum splitting to efficiently utilize the full spectrum of sunlight in converting from solar energy to electricity was demonstrated. Multi-junction solar cells are already efficient, but further gains are possible by splitting the solar spectrum laterally, rather than vertically, onto electrically isolated cells. A textured thin film was used to diffract two spectral bands to laterally displaced regions in the far field. The optimized optical element having multi-level textures was fabricated using 3D direct laser writing on photoresist. The fabricated samples were optically characterized and potential modifications to achieve even higher efficiencies were pointed out. Further, this thesis demonstrated a new display architecture that can alleviate problems associated with liquid crystal display (LCD) devices: substantial losses in optical intensity due to employed color filters and low ambient contrast ratio because of reflection of external light from the front surface. A luminescent film having quantum dots was placed inside an enclosed microcavity. The design for a high-contrast and high efficiency display comprised an enclosed cavity having a front wall and a back wall, where the front wall comprised a pinhole opening for emission of light from the cavity and the back wall was configured to transmit light into the cavity. The outer surface of the front wall was made to absorb substantially all optical wavelengths of externally incident light so as to appear black. The inner surface of the front wall and sidewalls were highly reflective to promote photon recycling within the cavity and light emission through the pinhole opening. Finally, although the single pixel demonstration served to optimize the optics within the cavity and study the physics of the proposed architecture, a micrometer sized pixel array was proposed since the current portable electronics industry demands displays with large pixel arrays, where each pixel is on the order of micrometers in size. An individually addressable micropixel array was proposed and fabricated using standard microfabrication techniques that can be integrated into commercial displays.
Issue Date:2018-10-02
Rights Information:Copyright 2018 Osman Cifci
Date Available in IDEALS:2019-02-07
Date Deposited:2018-12

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