A fluorescent organic triarylamine with a symmetric structure, 2,7-bis(N-α-naphthyl-phenylamino)-9,9- diethylfluorene (NPAEF) was synthesized using two methods, modified Ullmann coupling and modified palladium-catalyzed amination. An activated copper and a combination of Pd(OAc)2/P(t-Bu)3 and Pd(dba)2/P(t-Bu)3 were selected as catalysts to improve yields of reactions. These synthetic procedures were also successfully applied to an asymmetric 2-dimesitylboron-7-(N-phenyl-α-naphthylamino)-9,9-diethylfluorene (BNPEF). Photoluminescent emission peaks in solid film and in diluted solution of NPAEF were both observed at 461 nm, while the main emission peaks of BNPEF appeared at 422 nm in hexane, and at 480 nm in methanol. The double emission peaks of BNPEF in hexane reflected fine structure in the vibrational state. With an increasing polarity of solvent, the main PL emission peaks were red-shifted and vibrational fine structure disappeared. Additionally, energy levels of NPAEF were investigated and an electroluminescence (EL) device of ITO/PVK:NPAEF/Al was fabricated, which showed a turn-on voltage of 9 V and peaked at 462 nm. The EL spectrum was in good agreement with PL spectrum, which indicated that they were from the same emitting center in the device.
This paper reports an investigation on the electrical properties of thin film devices made by Copper(II) phthalocyanine derivative and polycarbonate (PC) composite. The conducting and injection mechanism are further discussed. Materials of a variety composition were prepared into the thin film via spin-coating. ITO and aluminum were used as the bottom and top electrode respectively. J-V characteristic was measured and the result demonstrates that at a small bias region an Ohmic contact was achieved. As the forward bias increased, the current became space charge limited. The result of AC impedance measurement indicates the device could be equivalent to a parallel RC system. The introduction of PC into the CuPc possibly reduces the charge overlapping between the aromatic rings and led to a reduction in the molecular interaction. Hence, the ac conductivity decreases sharply as PC composition increases. But no change in the transport mechanism is found.
WANG Ting-tingHE Zhi-qunZHENG Xiao-panWANG Yong-shengZHANG Chun-xiuZHANG Wen-guan
