Abstract
In the thesis, five imidazole derivatives with styryl group, PPIE, TPIE, NPIE, MBIE and PBIE have been synthesized. We adopt rigid phenanthrene and phenanthroline moieties to improve the thermal stability of the materials. All compounds exhibit high decomposition temperature of 411 ~497 ℃. Especially, PPIE possesses high Tg (190 ℃) with good morphology of thin film. The HOMO level of these materials is between the 5.35~5.75 eV, and the LUMO level is between 2.66~3.02 eV. In particular, PPIE exhibits the high fluorescent quantum yield (83%), which can harvest the excitons efficiently via Förster energy transfer from the host material (P1). The blue fluorescent device using P1 as a host and PPIE as a dopant performs the external quantum efficiency of 8.2%, a current efficiency (ηc) of 11.2 cd/A, a power efficiency (ηp) of 5.5 lm/W, and CIE coordinates of (0.15, 0.16), respectively. We successfully synthesized five imidazole derivatives incoperating anthracene moiety to be used as blue host matrials. These materials display highly twisted structure responsible for the low degree of aggregation in the thin film. The compounds exhibit high decomposition temperature of 335~436 ℃ and high glass trasition temperature of 94~148 ℃. The EL device featuring PPIA as an emitter exhibited the excellent external quantum efficiency of 4.1% with the CIE coordinates of (0.15, 0.09), and the turn-on voltage is merely 3.3 V. The device using PPIA as a host and BCzVBi as a dopant shows the external quantum efficiency of 7.9%, a current efficiency (ηc) of 9.0 cd/A, a power efficiency (ηp) of 4.9 lm/W, and CIE coordinates of (0.14, 0.12), respectively. Finally, we fabricated an optimized blue fluorescent device composed of PPIA doped with PPIE.The surface of PPIA . The device performs an external quantum efficiency of 8.6%, a current efficiency (ηc) of 12.3 cd/A, a power efficiency (ηp) of 4.5 lm/W, and CIE coordinates of (0.14, 0.17), respectively.