| 초록 |
Novel poly(p-phenylenevinylene) derivatives with a cyanophenyl as an electron-withdrawing group onto the polymer backbone, poly[2-(2’-ethylhexyloxy)-5-(4’-cyanophenyl)-1,4-phenylenevinylene] (PEHCNPV), and poly[2-dimethyloctylsilyl-5-(4’-cyanophenyl)-1,4-phenylenevinylene] (PSi8CNPV), were synthesized through the Gilch polymerization. These polymers were highly soluble in common organic solvents, and showed good thermal stabilities up to 400 oC. Surprisingly they showed very high glass transition temperatures above 180 oC, which is a great advantage to the EL device stability. The HOMO and LUMO energy levels of the polymers were quite lowered compared with the common PPV derivatives due to introducing an electron-withdrawing cyanophenyl group. The electroluminescence maximum peaks of PEHCNPV and PSi8CNPV were at 546 nm and 513 nm, respectively, when the light-emitting diodes of ITO/PEDOT/polymer/LiF/Al were fabrivcated. Especially, LED device with PSi8CNPV showed pure green emission whose CIE coordinate (0.330, 0.599) is very close to that of the standard green (0.30, 0.60) for high definition television (HDTV), with a maximum external quantum efficiency of 0.67% and a maximum brightness of 2900 cd/m2. |
