Electrochemical doping and the optical properties of light-emitting polymer materials and devices

The first three chapters of this dissertation serve as an introduction to the field of light-emitting polymers and polymer-based devices including materials, device construction, and measurement techniques. In chapter one I discuss the physical models necessary to understand semiconductivity in conjugated polymers. Chapter two reviews the device physics of several important applications. In chapter three I introduce the experimental techniques used in the following studies.; Two well established light-emitting polymer devices include the polymer LED and the polymer LEC. The LEC uses electrochemical doping to achieve the charge injection necessary for light emission, while the LED injects charge directly from contact electrodes. I use a technique employing simulations of interference effects in multilayered device structures, matching experimental device spectra to simulation in order to gain insight into the location of light emission within the device. In chapter four I use this technique to explore the thickness dependence of PLEDs. In chapter five I combine simulations of interference effects in LECs with studies of planar geometry devices, thereby providing information about the fundamental operating mechanism of these devices.; Several polymer-based applications include light-emitting electrochemical cells (LEC), electrochromic devices (ECD), and actuators, for which the operating mechanism depends heavily on electrochemical doping. Unfortunately, the doping of light-emitting polymers is not well understood. In chapter six I study the basic electrochemical doping reactions of one common light-emitting polymer, MEH-PPV. I explore factors affecting the fundamental doping reaction through cyclic voltammetry. Further, I investigate the optical properties of doped films in order to gain insight into the structural changes and changes in the energy band structure induced by doping.; Finally, I explore some unique functionalities of MEH-PPV, specifically electrochromic and thermochromic effects. Chapter seven presents a MEH-PPV based electrochromic device with a layered polymer/gel electrolyte structure that displays sharp contrast and high reversibility when biased at low operating voltages. In chapter eight I study the reversible, high-contrast thermochromic behavior of MEH-PPV gel films, occurring in a practically relevant temperature range and without phase or volume changes. (Abstract shortened by UMI.)...