C. Y. Chen, C. Tang
Nov 16, 2001
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Journal
Applied Physics Letters
Abstract
We have discovered two stericly hindered green coumarin derivatives which showed significantly better thermal stability and overall electroluminescence (EL) performance than those of the corresponding 3-(2-benzothiazolyl)-7-(diethylamino)-2H-1-benzopyran-2-one (C-6) and 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl- 2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]pyrano[6,7, 8-ij] quinolizin-11-one (C-545T). The strategic incorporation of bulky spacer t-butyl groups in these dopants considerably delays the onset of concentration quenching. In particular, 10-[2(5,7-di-t-butyl)benzothiazolyl]-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo-[l]pyrano[6,7,8-ij]quinolizin-11-one (C-545TB) with its superb thermal stability (Tg=142 °C; Td=327 °C), high luminance efficiency (∼13 cd/A), good Commission Interationale d’Eclairage (CIE) coordinates (x=0.30; y=0.64) and a nearly flat EL efficiency dependence on drive current stands out as one of the best choice of green dopants for use in the passive-matrix organic light-emit...