HIGH EFFICIENCY PLANAR SOLAR CONCENTRATORS AND NOVEL STRUCTURES FOR ORGANIC LIGHT EMITTING DIODES

Open Access
Author:
Price, Jared Scott
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
December 14, 2017
Committee Members:
  • Noel Christopher Giebink, Dissertation Advisor
  • Noel Christopher Giebink, Committee Chair
  • Thomas Nelson Jackson, Committee Member
  • Jerzy Ruzyllo, Committee Member
  • Jian Xu, Outside Member
Keywords:
  • OLED
  • LED
  • CPV
  • Photovoltaics
Abstract:
Given the continual rise of the global population and energy consumption, it is arguably more important now than ever to reduce the amount of power produced through the combustion of fossil fuels and to implement more efficient means of utilizing that energy. This thesis is broken into two parts, the first being focused primarily on a novel planar concentrating photovoltaic (CPV) architecture, while the second component is dedicated to understanding the physics of organic light emitting diodes (OLEDs) operating at high brightness, and methods of enhancing their stability and commercial viability. The common theme tying these seemingly disparate fields together is the goal of designing and implementing technologically, environmentally, economically, and socially sustainable technologies to allow for better use of the energy that we produce and consume. The primary contributions of the work herein are as follows. First, we demonstrate that planar CPV is capable of outperforming traditional flat-plate silicon PV on a performance basis. Second, we establish a facile approach to understanding efficiency roll-off OLEDs and LEDs by repackaging standard light-current-voltage (LIV) data into a series of easy-to-interpret plots. Third, we illustrate a method of converting organic electronics from 2D to 3D structures using kirigami, thereby opening a route to high aspect ratio, high performance OLEDs in novel form factors. Finally, we establish a route of coevaporating amorphous fluoropolymers with organic semiconductors to enable a significant increase in operational temperatures with little change in the optoelectronic characteristics of functional devices. We begin with a broad survey of the state of the global energy landscape, and suggest that low-cost solar power generated via CPV may be part of the solution to the world's future energy woes. The design principles and fundamental limits of a catadioptric planar microtracking CPV architecture are explored, and we find that in a sunny location like Phoenix, AZ, such a system would be capable of producing 1.7x more energy annually than a traditional flat-panel Si PV module. This work culminates in a fully automated CPV system <2 cm thick that operates at fixed tilt with a microscale triple-junction solar cell at >660x concentration ratio over a 140 degree field of view. In outdoor testing over the course of two sunny days, the system operated from sunrise to sunset, reached a peak power conversion efficiency exceeding 30%, and ultimately outperformed a commercial silicon solar cell on an energy per unit area basis, which points towards the feasibility of CPV as a possible alternative to silicon-based PV. The second portion of this thesis provides a brief introduction the device physics of OLEDs as well as an overview of display and lighting applications. We develop and test an AC harmonic light and current based analytical framework to better understand OLED efficiency roll-off, and subsequently extend this technique to light emitting diodes with inorganic emitters. Various approaches are taken to bring OLEDs from a two-dimensional form-factor into the third dimension, which results in OLEDs with an increased brightness on a per-area basis as well as novel geometries and shapes. Finally, we endeavor to increase the morphological stability of OLEDs by co-evaporating an amorphous fluoropolymer into their transport layers, which results in improved current-voltage characteristics, addition to a >60 degreeC boost in device operating temperature. When taken together, these results all indicate that a range of simple solutions exist to vastly improve the performance of OLEDs.