259 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. DOI: 10.4018/978-1-60960-186-7.ch017 Chapter 17 Dominant Spin Relaxation Mechanisms in Organic Semiconductor Alq 3 Sridhar Patibandla Virginia Commonwealth University, USA Bhargava Kanchibotla Virginia Commonwealth University, USA Sandipan Pramanik University of Alberta, Canada Supriyo Bandyopadhyay Virginia Commonwealth University, USA Marc Cahay University of Cincinnati, USA INTRODUCTION Recent interest in the field of “spintronics” stems primarily from the desire to use the spin degree of freedom of a single electron, or a collection of electrons, to store, process, detect and com- municate information. Digital information (in the form of binary bits 0 and 1) is encoded in the spin polarization of electron(s), then “processed” using spin-spin or spin-orbit interactions, subsequently ABSTRACT We have measured the longitudinal (T 1 ) and transverse (T 2 ) spin relaxation times in the organic semi- conductor tris(8-hydroxyquinolinolato aluminum) - also known as Alq 3 - at different temperatures and under different electric felds driving current. These measurements shed some light on the spin relaxation mechanisms in the organic. The two most likely mechanisms affecting T 1 are hyperfne interactions be- tween carrier and nuclear spins, and the Elliott-Yafet mode. On the other hand, the dominant mechanism affecting T 2 of delocalized electrons in Alq 3 remains uncertain, but for localized electrons (bound to defect or impurity sites), the dominant mechanism is most likely spin-phonon coupling.