Design, Synthesis, And Properties Of Organic Light-Emitting Materials Based On Pyrene

Organic light-emitting diodes (OLED) have been considered to be one of the most promising display technologies and may replace liquid crystal displays. This is because OLEDs have many advantages for the potential applications, such as active emission, wide view angles, low drive voltages, and can implement flexible display. The development of information technologies requires advanced materials to support. One of the key challenges on the path to commercializing OLEDs is to explore high-performance electroluminescence (EL) materials. Based on the survey of the development and the state of the art of EL materials, several novel EL materials based on pyrene were synthesized and their EL properties were studied. The main researching contents are as follows:1. X-shaped pyrene derivatives containing alkyne bondsConsidering the tradeoff between luminescence enhancement and charge carrier mobility, two X-shaped compounds based on pyrene were synthesized through Suzuki and Sonogashira coupling reactions. Their photophysical, electroluminescent and field-effect charge transport properties were studied. The two compounds show high fluorescence yields. In addition, Compound 9 displays the unique PL characteristics that its fluorescence spectra can be reversibly converted from 610 nm to 574 nm in the solid state. Electroluminescent devices employing 7 and 9 as the emitting layer were fabricated, and the device based on 7 exhibits better EL performances. Field-effect hole mobility of up to 4.0×10-3 cm2V-1s-1 for 7 were obtained. The EL performance is better than those of the pyrene materials in which theπaggregate is completely prevented. Therefore, the design of highly efficient organic light-emitting materials based on pyrene should balance the relationship between fluorescent enhancement and charge transfer.2. Aggregation-induced enhanced emission-active pyrene derivativesTwo new pyrene-based fluorophores, namely 1-[4-(2,2-diphenylvinyl)phenyl]pyrene (PVPP) and 1,3,6,8-tetrakis[4-(2,2-diphenylvinyl)phenyl]pyrene (TPVPP), were synthesized. PVPP exhibits an interesting aggregation-induced enhanced emission behavior. Despite with same substituent, TPVPP shows a different fluorescent behavior. The distinct fluorescent behavior was discussed by analyzing their crystal structures. The results manifest that the weaker fluorescence of TPVPP in the solid state is ascribed to multiple intermolecular C-H…πinteractions (12 interactions for each molecule). The two compounds show good thermal stabilities and high glass transition temperature. The performance of devices based on PVPP and TPVPP were investigated by utilizing them as emissive layers. The devices based on the two materials exhibit maximum luminescence of 30996 and 103835 cd m-2, maximum current efficiency of 2.06 and 5.19 cd A-1, and power efficiency of 1.06 and 3.38 lm/W, respectively. The results demonstrate that PVPP and TPVPP are promising EL materials.3. A-shaped pyrene derivativesA-shaped geometry configuration of Troger's base is not easy to formπ-πclose stacking, which commonly results in fluorescence quenching in the solid state. Pyrene has attracted significant attention as a candidate in OLEDs because of its excellent fluorescent properties. Considering the two aspects, we synthesized a A-shaped compound based on pyrene (TBPy). Its photophysical, thermal, electrochemical and electroluminescent properties were studied. The experiment results indicate that Troger's base plays an important role in suppressing theπaggregates formation between planar pyrene moieties and can improve the stability of amorphous films. TBPy not only shows high fluorescence quantum yields in dilute solutions, but also shows strong photoluminescence in the solid state. After storage for four months under ambient conditions, the amorphous film of TBPy shows no trend of crystallization.