| Other Abstract | In present dissertation, hole transport in phosphorescent dyes, bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1Hbenzoimidazol-N,C3) iridium(acetylacetonate) [(fbi)2Ir(acac)], tris(2-phenylpyridine) iridium [Ir(ppy)3], tris[1-phenylisoquinolinato-C2,N]iridium [Ir(piq)3], bis(4,6-difluorophenyl)-pyridina-to-N,C20]-picolinate (FIrpic) and bis（4’,6’-difluorophenylpyridinato）tetrakis(1-pyrazolyl)borate (FIr6)] doped host molecule films of [N,N-diphenyl-N,N-bis(1-naphthylphenyl)-1,1 -biphenyl-4 ,4 -diamine (NPB), 4,4,4-tri(Ncarbazolyl)triphenylami (TCTA) and 4,4’-N,N’-dicarbazole-biphenyl (mCP)] are systematically investigated by using admittance spectroscopy (AS) method and important conclusions are drown.
1. Hole mobility of phosphorescent iridium complexes, bis(2-(9,9-diethyl-9 H-fluoren-2-yl)-1- phenyl-1Hbenzoimidazol-N,C3) iridium (acetylacetonate) [(fbi)2Ir(acac)]、Tris(2-phenylpyridine) iridium [Ir(ppy)3] and tris[1-phenylisoquinolinato-C2,N]iridium [Ir(piq)3] doped fluorescent host NPB and TCTAfilms, as well as FIrpic and FIr6 doped mCP film, were investigated. Important results are obtained. (1) For thicker films (>300 nm), the electric field dependence of hole mobility is, as expected, positive, i.e., the mobility increases exponentially with the squareroot of electric field. However, for thin films (<300 nm), the electric field dependence of hole mobility is negative, i.e.the hole mobility decreases exponentially with the electric field. (2) For (fbi)2Ir(acac) doped NPB film, the dopant molecule function as hole traps, and lower the hole mobility. For thickness at the order 100 nm, the hole mobility decreases exponentially with the square root of the electric field. (3) For Ir(piq)3 doped NPB film around 100 nm thick, the mobility decreases exponentially with the square root of the electric field,. In general, the variation of mobility with the doping concentration is insignificant. For an applied bias of 9 V, the mobility varies in the range of 1.310-52.410-5 cm2/Vs for a wide doping concentration range of from 1.0 wt.% to 9.0 wt.%. In addition, the dependence of mobility on the temperature is weak. For a doping concentration of 3.0 wt.% and an electric field of 5×105 V/cm, the mobility varies in the small range of 1.8×10-5～2.1×10-5 cm2/Vs in a large temperature range of from 78K to 300K. (4) For (fbi)2Ir(acac) and Ir(ppy)3 doped TCTA films, in the case of light doping, the mobility decreases with the square root of the electric field, w... |
