Excimer Formation by Electric Field Induction and Side Chain Motion Assistance in Polyfluorenes
作者:Hsin-Hung Lu、Ching-Yang Liu、Tzu-Hao Jen、Jin-Long Liao、Hao-En Tseng、Chih-Wei Huang、Ming-Chin Hung、Show-An Chen
DOI:10.1021/ma051594z
日期:2005.12.1
For poly(9,9-di(6-(2-(3-oxetanyl)butoxyl)hexyl)-2,7-fluorene) (POBOHF), measurements on field induction-thermally stimulated current (FI-TSC) and electroluminescence (EL) under a wide temperature range demonstrate that electric field induction (FI) accompanied by side chain motion can lead to a formation of excimers, which contribute to a growth of a green component in the EL spectrum. This phenomenon also happens to poly(9,9-di-n-octyl-2,7-fluorene) (PFO), especially under long-term operations with higher electric fields (1 x 10(6) V/cm), copolymers of OBOHF and FO (PF-1/1 and PF-1/3), and even cross-linked POBOHF. The higher polarity of the side chain in the polyfluorenes (PFs) can cause a more pronounced FI effect. For POBOHF, the green component can even dominate after a few cycles of device operation. Lowering the content of cross-linkable commoner in the copolymers from 50 to 25 mol % only moderately suppresses the formation of FI excimers.