Photo-physics of electroluminescent organic semicondustors

• Main Authors: Chia-Hsun Chen, 陳家勳
• Other Authors: Hsin-Fei Meng
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/az97t7

博士 === 國立交通大學 === 物理研究所 === 92 === We study three topics on the photo-physics of organic semiconductors:mechanism for photo-current generation for the excitation below the energy gap;electroluminescence yield improvement by magnetic doping; and device simulation for color-tunable multilayer organic light-emitting diode (LED). Chapter 2 first reviews the controversial photo-current induced by photo-excitation below band gap. Auger exciton dissociation through deep level defects was proposed as the possible mechanism. We calculate the inverse process of Auger process, impact ionization, as well. A feasibility of the electroluminescence for unipolar light-emitting diode based on the impact ionization process is presented. Chapter 3 presents a method to improve the electroluminescence efficiency of conjugated polymer LED theoretically. Doping magnetic complexes into polymer LED can turn on the transition channel between radiative singlet exciton and nonradiative triplet exciton. With suitable concentration for the doped magnetic complexes, it is possible for the singlet exciton ratio being beyond the spin independent value 25% and reach up to 80%. Chapter 4 presents device simulation for multilayer organic LED. Two device structures are shown to have the possibility to tune the luminescence color from orange-red, green, then to blue as the bias voltage increases. These structures provide a potential solution for full-color display with organic material other than the common technology by ink-jet printing method.