| Summary: | 博士 === 國立成功大學 === 化學系碩博士班 === 94 === Organic light-emitting diodes (OLEDs) have potentials for application in the flat panel display and have received vast attentions. This work focuses on synthesizing various green and red phosphorescent emitters based on iridium complexes.
Firstly, four novel red phosphorescent emitter compounds bis(1-phenyl- isoquinolinato-N,C2’)iridium(acetylacetonate), (piq)2Ir(acac), bis(1-(1’naphthyl) isoquinolinato-N,C2’)iridium(acetylacetonate), (1-niq)2Ir(acac), bis(1-(2’-naphthyl) isoquinolinato-N,C2’)iridium(acetylacetonate), (2-niq)2Ir(acac), and bis(1-phenyl- 5-methyl-isoquinolinato-N,C2’)iridium(acetylacetonate), (m-piq)2Ir(acac), have been synthesized and fully characterized. Electroluminescent devices with a configuration of ITO / NPB / CBP : Dopant / BCP / AlQ3 / LiF / Al were fabricated. All devices emitted in the red region with an emission ranging from 624nm to 680nm. (m-piq)2Ir(acac) shows a maximum brightness of 17164 cd/m2 at a current density of J = 300 mA/cm2 and the best luminance efficiency of 8.91 cd/A at a current density of J = 20 mA/cm2. (1-niq)2Ir(acac) exhibits pure-red emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates (x=0.701, y=0.273).
Secondly, novel red phosphorescent emitter bis(4-phenylquinazolinato-N,C2’) iridium(acetylacetonate) [(pqz)2Ir(acac)], bis(1-(1’-naphthyl)-5-methylisoquinolin ato-N,C2’)iridium(acetylacetonate) [(1-mniq)2Ir(acac)] and bis(1-(2’-naphthyl)- 5-methylisoquinolinato-N,C2’)iridium(acetylacetonate) [(2-mniq)2Ir(acac)] have been synthesized and fully characterized. The electronegative effect of (pqz)2Ir(acac) ligand shows almost the same influence as the extended π-conjugation effect of (2-mniq)2Ir(acac). Density functional theory (DFT) was applied to calculate the Kohn-Sham orbitals of HOMOs and LUMOs in the iridium complexes to illustrate the N(1) electronegative atom effect. Finally, lowest triplet state (T1) energies calculated by time-dependent DFT (TDDFT) were compared with the experimental electroluminescent data. The calculated data for the iridium complexes agreed fairly well with experimental data. Electroluminescent devices with a configuration of ITO / NPB / CBP : dopant / BCP / AlQ3 / LiF / Al were fabricated. The device using (pqz)2Ir(acac) as a dopant showed deep-red emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates x = 0.70, y = 0.30.
Thirdly, we developed a new process at high vacuum (5×10-5 torr) and high temperature (300℃) to produce meridional iridium complexes from the dimer; interestingly, mer-Ir(m-ppy)3 overthrows the concept of poor efficiency and shows excellent efficiency that is almost equal to fac-Ir(ppy)3, fac-Ir(m-ppy)3 and (ppy)2Ir(acac). In this approach, we have found that mer-Ir(m-ppy)3 in fact results in a blue shift with respect to fac-Ir(ppy)3 and produces a fairly pure green emission. Electroluminescent devices with a configuration of ITO / NPB / CBP : dopant / BCP / AlQ3 / LiF / Al were fabricated. The device using mer-Ir(m-ppy)3 as a dopant showed green emission with 1931 CIE (Commission International de L’Eclairage) chromaticity coordinates x = 0.31, y = 0.59. This result suggests us a new direction in developing novel emitter for OLEDs.
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