The Research Of White Organic Light Emitting Devices Based On Bipolar Mixed-hosts

Organic Light Emitting Devices has attracted wide attention due to its high efficiency,low turn-on voltage,less blue emission,surface light emission and can easily prepared on flexible substrates.However,the commercial promotion of OLEDs is still restricted by the complexity of the device structure and the low efficiency.To solve these problems,in this paper,used two different organic materials as a mixture to adjust the carrier balance of the host which will improve the photoelectric performance of the OLEDs and further simplify the structure of the device.First,the 3,5-Bis(3-(9H-carbazol-9-yl)phenyl)pyridine(35DCzPPy)and 2,4,6-Tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine(diphenylphosphinyl)phenyl]-1,3,5-triazine(PO-T2T)were used as the mixed host,and dropped Bis(3,5).-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(Ⅲ)(FIrPic)as blue light emission to prepare blue light OLEDs.The current efficiency of 15cd/A was achieved through the generation of exciplex and the improvement of 35DCzPPy carrier balance.Based on this study,the traditional hole transfer host material 1,3-Bis(carbazol-9-yl)benzene(commodity name:MCP)and the 4,6-Bis(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine(3,5-di(pyridin-4-yl)phenyl)-2-methylpyrimidine(commodity name:B4PYMPM)were used as the mixed host,and dropped FIrPic to prepare the blue light OLEDs.Through the optimization of the host structure,the device performances were improved and got the highest blue light OLEDs with a current efficiency of 29.24cd/A.Then by introducing the yellow light ultra-thin layer Iridium(Ⅲ)bis(4-(4-tert-butylphenyl)thieno[3,2-c]pyridinato-N,C2')acetylacetonate(commodity name:PO-01-TB)and adjusting the thickness of the ultra-thin layer,the highest power efficiency(71.3lm/W)of the white light device was obtained when the PO-01-TB layer was 0.1nm.And on the flexible substrate PET,the power efficiency of white OLED devices was still as high as 41lm/W.When the luminance of the device increased from1000 cd/m~2 to 10000 cd/m~2,the color coordinates of the device change from(0.37,0.45)to(0.38,0.47).The white light OLEDs was very stable.