The Research Of White Organic Light Emitting Diode Spectral Characteristics

Since 2003,the development of organic electroluminescent display(OLEDs)has been in the ascendant.Due to its features of high speed,high contrast,low energy consumption,and flexible display,it has become a trend of display technology.But,in the manufacturing process,there are great difficulties in making trichromatic OLEDs with large screens and high resolution display,to which the combination of white OLEDs with color filters will be an effective solution.However,at present,white OLED devices are all trapped by poor CIE color coordinates and low current efficiency.Therefore,developing a white light device with high efficiency has become the key to the problem.For this reason,this thesis designed a double-tandem white OLED device which mixes a bottom-emitting blue light and an orange light together,worked on the white light spectral adjustment and aimed to figure out how dielectric layer throws its effects on light extraction.The details are as follows.1.To create a high efficiency white organic electroluminescent device,A high-efficiency white organic light emitting diode was designed by matching the energy level structures in organic materials;based on the carrier balance theory,the best thickness of blue light emitting was founded by optimizing the thickness of the blue light emitting layer;combined with energy transfer theory,this thesis found the best emission structure of red and green light emitting layer by changing the red light doping ratio and the thickness of the red and green light emitting layer;after optimizing the injection ability of charge-generating layer,This thesis recognized the law of white spectral adjustment and found the optimal charge-generation layer structure;in accordance with the triplet-triplet quenching effect,hole transport material of high triplet energy level is put in front of the blue light-emitting layer,thus enhancing the intensity of the blue light;and through the weak micro-cavity effect,the entire device's optical path was re-adjusted.As a result,this thesis produced a current efficiency of 45 cd/A,CIE(0.31,0.33)white OLED devices.2.Considering that in the actual bottom-emitting white OLED display,the lights are all emitted through the SiNx and SiO2 films of the TFT drive circuit,a single dielectric SiNx film and a SiNx/SiO2 dual thin film dielectric layer are disposed between the glass substrate and the anode ITO.By changing the thickness of the dielectric layer,this thesis discovered the influence of dielectric layer on white light emission.And it was found that a SiNx monolayer with a thickness of 100 nm and a SiNx/SiO2 dual dielectric layer with a thickness of 50 nm/120 nm have a strong enhancement effect on green light emission;a SiNx/SiO2 double dielectric layer with a thickness of 50 nm/260 nm have a strong enhancement effect on red light emission.