Synthesis And Property Research Of D-A Type Organic Small Molecule Luminescent Materials With Oxadiazole As Acceptor Unit

Organic electroluminesence display(OLED)had been widely developed due to their excellent performance,promising applications in full-color flat-panel display technology and light-emitting electrochemical cell(LEC).The bipolar host material has the advantages of low driving voltage and high efficiency.In the emission layer of the OLED device with the bipolar host material,holes and electrons achieve a good balance,which improves the device performance.In this paper,we designed and synthesized a series of carbazole-oxadiazole-based small-molecule host materials and explored their luminescent properties.The specific research contents of this paper are as follows:(1)Three D-A type organic light-emitting materials were designed and synthesized using9-(2-bromophenyl)carbazole as the raw material,and their thermodynamic,photophysical and electrochemical properties were studied.The research results showed that all of the three materials showed good thermal stability,and they had a high glass transition temperature T_g,indicating that they had good morphological stability.All of these materials emitted deep blue fluorescence in solution.This series of materials all exhibited reversible redox behaviors and could form stable cations and anions,indicating that these materials had ambipolar carrier transport properties.(2)Five D-A organic light-emitting materials were designed and synthesized using2,6-difluorobenzonitrile and carbazole as raw materials,and the thermodynamics,photophysics,electrochemistry and the performance of OLED devices were studied.The results showed that the thermal stability of the five materials was very good,the high values of glass transition temperature(T_g)and decomposition temperature(T_d)meaned that they could withstand vacuum thermal sublimation and inhibit aggregate formation,while maintaining the amorphous nature of the film properties.These materials emitted light in the deep blue range.All of the five materials exhibited reversible redox behaviors,indicating that the target product could form stable cations and anions upon oxidation or reduction,which further suggested bipolar carrier transport properties.Cz OXD-246,j-Cz OXD-2,j-Cz OXD-246 were selected as the host materials of the light-emitting layer to prepare several red Ph OLED devices.Through the device characterization results,it was found that the maximum brightness reached 19491 cd/m~2for j-Cz OXD-2,the highest current efficiency was j-Cz OXD-246 with a maximum current efficiency of 15.07 cd/A.To further study the optoelectronic properties of bipolar host materials,these three materials were used as the host material of the light-emitting layer to prepare several green Ph OLED devices,the device characterization results showed that the maximum brightness reached 31486 cd/m~2for j-Cz OXD-246,and the j-Cz OXD-246 had the highest current efficiency with a maximum current efficiency of 17.76 cd/A.(3)Four D-A type organic light-emitting materials were designed and synthesized using9-(4-bromophenyl)carbazole as raw material,and the thermodynamic,photophysical,electrochemical properties and the performance of OLED devices were studied.The research results showed that the thermal stability of the four materials was good,and these molecules had good glass transition(T_g)and decomposition temperature(T_d)values,presumably they could withstand thermal sublimation under vacuum and remain amorphous during device operation.All of these materials emitted deep blue fluorescence in solution and exhibited reversible redox properties,indicating that the four materials had ambipolar carrier transport properties.To further study the optoelectronic properties of bipolar host materials,these four materials were used as the host material of the light-emitting layer,several red Ph OLED devices were prepared.Through the device characterization results,it was found that the maximum brightness reached 26249 cd/m~2for d-Cz OXD-26,among which,d-Cz OXD-3 had the highest current efficiency with a maximum current efficiency of 11.15 cd/A.Four kinds of materials were used as the host material of the light-emitting layer to prepare several green Ph OLED devices.The device characterization results showed that the maximum brightness reached 33021 cd/m~2for d-Cz OXD-246,among which,d-Cz OXD-24 had the highest current efficiency with a maximum current efficiency of 20.11 cd/A.