Study On Effects Of Interlayer On Color Stability For White Organic Light-emitting Diodes

Organic light-emitting diode(OLED)attaches many advantages such as ultra-thin,low consumption,green,flexible,folding and etc.These make OLED be a hot-spot of recent market and scientific research area.To research the effects of interlayer between emission layers on white organic light-emitting diode(WOLED)and to obtain a white device with a highly stable color purity,some processes have been done in this work.Firstly,the effects of the material match between host and electron transport materials which affect on the performances of devices have been studied based on a blue OLED by replacing the single emission layer with double blue emission layers.The study shows that a part of excitons generated by Firpic can be returned to the host material because the triplet energy level of TmPyPb is close to that of Firpic.It forms triplet excitons of host material,occurs resonance effect,then improves the energy utilization rate.Next,based on the above conclusion,green and blue emission layers close to cathode and red emission layer close to anode are the key to design this WOLED whose host materials are TmPyPb for blue and green emission layers similarly.It is efficient for green emission layer to utilize excitons from TmPyPb and Firpic according to the comparison between devices.Then,the research for studying the influences of interlayer on this white device indicates that it is similar to emit mainly red for the devices with no interlayer and green and blue emission layers inserted with 2 nm TmPyPb,respectively.The light components are green and blue when the 2 nm TCTA interlayer is inserted between blue and red emission layers.The device with two interlayers achieves a near standard white and maximum efficiency of 22.56 cd/A through the exciton distribution,energy transfer of Dexter and F?rster,and the amount of the three primary colors.Finally,a series of WOLEDs have been fabricated to discuss the effects of TmPyPb on color stability by changing the thickness of TmPyPb between the green and blue emission layers.It is discovered that the intensity of blue is the continuously highest and the intensities of green and red are inverse to the thickening of TmPyPb.The stable color device is obtained when the thickness of TmPyPb exceeds 4 nm,which shows the color coordinate of(0.33,0.36)under the current densities of 10 mA/cm~2,30 mA/cm~2,and 100mA/cm~2.The CIE(Commission Internationale de L'Eclairage)coordinates and color rendering index are influenced by exciton diffusion and quenching which follow with the different thickness of TmPyPb under varied current densities.