Abstract
Part I : A series of oligo(phenylenevinylene) (OPV) derivatives with finite conjugation units were prepared in short steps from few building blocks. The central and terminal aryl groups of these OPV dyes contain a cyano and Ph2N substituents respectively, which affect color of fluorescence. The wavelength ranges from 472 nm (blue) to 614 nm (red) depending on the position of the cyano group. Part II : We report the synthesis and OLED devicesof a series of iridium-phenyl-1- isoquino line complexes with fluoro-substituents on the isoquinoline or phenyl groups. Among the studied complexes, strong absorption feature in the region of 440-490 nm was assigned to spin-forbidden 3MLCT bands, of which the extinction coefficients are comparable to those of spin-allowed 1MLCT bands, indicative of an anomalously strong spin-orbital coupling. Upon excitation, these complexes exhibit a single phosphorescent emission band in red region (595-631 nm) with excited state lifetime 1.04-2.46 μs in CH2Cl2 and 0.15-0.44 μs in solid film respectively. The short radiative lifetime greatly circumvents triplet-triplet annihilation in their OLED devices. For the parent complex Ir(piq)2(acac) (Ir-I-1), an excellent external quantum efficiency of ca. 7.0 ％ can be maintained at high current (J = 400 mA/cm2) to achieve a brightness 25,000 cd/m2 (x=0.68, y= 0.32) at 14 V. Among various fluoro derivatives of complex Ir-I-1, Ir(p-fiq)2(acac) (Ir-I-3) (p-fiq = phenyl-1-5-fluoro-isoquinoline) is superior to complex Ir-I-1 with regard to EL-performance because it is not only brighter at low voltages (1883 cd/m2 at 7.1 V; 8320 cd/m2 at 9.0 V) but also shows an external quantum efficiency of ca. 6.50 at high current (J = 400 mA/cm2). The maximum brightness is 38,218 cd/m2 (x = 0.68, y = 0.31) with the full width at half maximum (FWHM) only. 50 nm at 14 V. Complex Ir-I-3 is the first red phosphor that performs comparably to commercial blue and green OLED emitters.