Development Of Benzosilole Optoelectronic Materials And Their Applications In Deep Blue OLED Devices

Organic light-emitting diodes（OLEDs）have gradually become the mainstream of the display field due to their unique advantages of self-illumination,wide color gamut,low energy consumption,flexible bendability and so on,leading the development of display and lighting technology.Blue light-emitting OLEDs are important constituent components in white light and high color rendering OLED devices.Therefore,the development of efficient and stable optofunctional materials applied in blue light-emitting OLEDs is of great significance to the development of OLED devices.In this paper,electron-donor/acceptor units are introduced in the blue luminescent benzosilole with excellent electron transporting ability,we studied the synthesis of substitution modification at different structural positions of benzosilole and their photoelectronic properties.We studied the photoelectronic properties of 1-position methyl or phenyl-substituted and 2-position electron-donor carbazole-substituted benzosilole compounds and their applications in electroluminescent devices.By constructing the molecular structure of type D-A,the effects of different electron donors（carbazole,acridine units）,the number of electron donors and the molecular configuration on the photophysical properties of benzosilole modified by the same electron acceptor（triazine）were studied,and the application prospect of these optoelectronic materials in OLED devices was explored.The specific research contents are as follows:（1）The electron donor carbazole substituted and methyl/phenyl substituted benzosilole derivatives Cz-Me BS and Cz-Ph BS were synthesized,and the molecular structures were characterized.We studies the thermal properties,electrochemical and photophysical properties of these two molecules.Photophysical experiment results show that both compounds emit deep blue light（～432 nm）in aggregated state,and their luminescence mechanism is conventional fluorescence.Combined with theoretical calculations,the results reveal that these two compounds have wide HOMO-LUMO energy gaps（～3.2 e V）and good electron transporting property.Doped deep blue OLED devices were fabricated by using the deep-blue light-emitting material Cz-Ph BS as the guest dopant.Among them,the deep blue OLED device with high doping concentration of Cz-Ph BS（21.56%）has the best performance with a maximum EQE of 4%.After the turn on of the device,the maximum peak of the device’s electroluminescent spetrum is 434 nm,and the CIE color coordinate is（0.151,0.076）under the voltage changing from 3 to 10V,indicating that the device has good electroluminescent stability.The preliminary application results of the phosphorescent OLED device prepared by Cz-Ph BS as the host material and Ir（ppr）₃ as the guest dopant show that the maximum emisstion peak of the electroluminescent spectrum at the voltage of 5 V is 512 nm and the CIE color coordinates of the device is（0.297,0.458）,which realizes the OLED device characterization of the green emitting phosphorous material Ir（ppy）₃.（2）The electron acceptor triazine was introduced at the 1-position of benzosilole,and the electron donor（carbazole or acridine）was introduced in the 2-and 3-positions,and the D-π-A structure of double-substituted,electron donor-benzosilole-electron acceptor was constructed to synthesize two compounds DCz-BS-TRZ and DDMAc-BS-TRZ.We characterized their molecular structures.Experimental results combined with theoretical calculations show that compared with single-substituted benzosiloles,the double-substituted benzosiloles with D-π-A structure have smaller HOMO-LUMO energy gaps（～2.5 e V）and their emission are red-shifted.Among them,the acridine double-substituted benzosilole DDMAc-BS-TRZ has better thermal stability with a decomposition temperature of 372?C and higher fluorescence quantum yield（36.6%）in the aggregated state.Furthermore,as compared to the solution state,this compound in the aggregated state has a fluorescent lifetime of 16μs,which indicates the characteristic of aggregation-induced lifetime increases.This result proves that for the first time,a long lifetime luminescent benzosilole compound has been succsussfully developed.