Insight into the Mechanism and Outcoupling Enhancement of the Excimer Associated White Light Generation
Journal
Chemical Science
Journal Volume
7
Journal Issue
6
Pages
3556-3563
Date Issued
2016
Author(s)
Ying-Hsiao Chen
Kuo-Chun Tang
Jiun-Yi Shen
Yu-Sin Wu
Shih-Hung Liu
Chun-Shu Lee
Chang-Hsuan Chen
Tzu-Yu Lai
Wen-Yi Hung
Min Jiao
Chen Y.-T
Abstract
Fundamental insight into excimer formation has been gained by using 9,10-bis[4-(9-carbazolyl)phenyl]anthracene] (Cz9PhAn) as a probe. Cz9PhAn exhibits a highly emissive blue fluorescence in solution and is found to emit a panchromatic white light spectrum (400-750 nm) in film, powder and single crystal, in which an additional excimer band appears at ∼550 nm. Detailed structural analyses, emission relaxation dynamics and a theoretical approach conclude the formation of an anthracene∗/phenyl ring excimer through an overlap between π∗ (anthracene) and π (phenyl ring) orbitals in a face-To-edge stacking orientation. The rate of excimer formation is determined to be 2.2 × 109 s-1 at room temperature, which requires coupling with lattice motion with an activation energy of 0.44 kcal mol-1. Exploiting Cz9PhAn as a single emitter, a fluorescent white organic light emitting diode (WOLED) is fabricated with a maximum external quantum efficiency (ηext) of 3.6% at 1000 cd m-2 (4.2 V) and Commission Internationale de L'Eclairage (CIE) coordinates of (0.30, 0.33). The white-light Cz9PhAn reveals a preferred orientation of the transition dipole moment in the emitting layer to enhance light outcoupling. This non-doped, single component (Cz9PhAn) WOLED greatly reduces the complexity of the fabrication process, rendering a green and cost-effective alternative among the contemporary display/lighting technologies. © The Royal Society of Chemistry 2016.
Other Subjects
Activation energy; Anthracene; Cost effectiveness; Fluorescence; Light emitting diodes; Organic light emitting diodes (OLED); Single crystals; Contemporary displays; External quantum efficiency; Preferred orientations; Stacking orientation; Theoretical approach; Transition dipole moments; White organic light emitting diodes; White-light generation; Optoelectronic devices
Type
journal article