Synthesis And Study Of Electroluminescent Properties Of Dendritic Carbazole Derivative

As a bright future displaying technique, organic light-emitting diodes (OLEDs) have attracted more and more attention by particular advantages such as low cost, fast response, high luminescence, wide view angle, low driving voltage, flexible substrates and so on for about 20 yeas. In order to achieve full-color display, red, green and blue light-emitting materials are essential as three primary colors. Up to now, blue and red light-emitting materials show poorer performance than that of green ones in red-green-blue tricolor phosphor used in fabrication for their poor thermal stabilities and low life. So the currently major efforts research are focused on searching for new blue light-emitting materials which have good luminescence performance and thermal stabilities.Carbazole and their derivatives have received more attention as materials due to their excellent performance. Recently, series of productions of the carbazole derivatives show high hole transporting ability, glass transformation temperature and good brightness. In this paper carbazole was chosen as the basic molecular construction unit, and three dendritic carbazole derivatives CBP-G1, CBP-G2 and CBP-G3 with big conjugate system were designed and synthesised. Their structures were confirmed by 1H NMR and MALDI-TOF-MS. Among the three compounds, CBP-G2 and CBP-G3 have not been reported in literature.Their photoelectric properties were determined by Ultraviolet-visible Absorption Spectra, Photoluminescent Spectra and Cyclic Voltammetry. Their thermal stability were investigated by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The results showed that:All these compounds exhibited photoluminescence (PL) with maxima in 400 nm which is within the limits of blue emitting; CBP-G2 and CBP-G3 have high thermal stabilities for their glass transition temperature are 302℃and 377℃and the decomposition temperature are 502℃and 517℃respectively. Non-doped OLEDs were fabricated by spin coating method and their electroluminescent properties were investigated. The OLED structure of new blue light-emitting materials was ITO/CBP-G1, CBP-G2 or CBP-G3 (40 nm)/TPBI (30 nm)/LiF (1 nm)/Al (200 nm).