Study About Improving The Performance Of Oled By Doping And The Theoretical Research On Improving Chroma Of White OLED

Organic light-emitting device(OLED) have become a hot spot in flat panel and solid-state lighting technology research in recent years, owing to their excellent properties, such as wide-viewing angle, low power consumption, wide material sources, flexible display in large area and environmental friendliness etc. Due to the low mobility of common organic materials, the doping increased the conductivity of organic materials and reduced the driving voltage of the OLED. With the progress of human civilization, the requirements for illumination are not only for brightness but for the influence on physiology and psychology. In this study, we improve the electroluminescent performances of OLED by different electrical doping, and study the theoretical on improving chroma of white OLED based on the present situation and problems of white OLED in the indoor lighting field at the same time. The main contents involved in this dissertation are listed as follows:1. We focus on increasing the efficiency of carrier injection and transport in OLED and improve the performances of the devices base on green phosphorescent materials Ir(ppy)3. Firstly the efficiency of hole injection and transport in OLED was increased utilizing the electron acceptor MoO3 as the p-type dopant doped into a hole transporting material TAPC. The fabricated devices exhibit a higher current density and a lower driving voltage, the luminance reaches 3999 cd/m2 at 4 V, more than 4.1 times of that of the device without doping. Then we utilizing the CsN3 as the n-type dopant doped into a electron transporting material BPhen for producing an efficient effect of n-doping. As a result, the turn-on voltage was decreased, and the brightness and the luminous efficiency of the device was improved. The device shows a turn-on voltage of 2.41 V, the maximum current efficiency reaches 54.77 cd/A and the maximum power efficiency reaches 66.12 lm/W at 2.6 V, which are obviously superior to those of the device without doping. Finally, we study the effect of a new type of organic n-dopant MeOPBI on device performance. The results show that the electronic injection ability of Bphen:MeOPBI doped layer is less than that of the conventional LiF-Al cathode. Therefore, it is necessary to add a electron injection layer in front of the cathode in order to further reduce the electron injection barrier and obtain better performance of the device when the MeOPBI is used as the n-type dopant.2. Using MATLAB to write a Color rendering index(CRI) calculation program, and calculate the CRI of the combination of a variety of tri-chromatic wavelength. We get an optimized tri-chromatic OLED spectrum with low color temperature and high color. The spectrum is produced from fitting of tri-chromatic with the peak wavelength in 460 nm, 540 nm and 620 nm, which present Gaussian distribution according to the radiation intensity ratio of 1:3:5.3 with the full width at half maximum of 63 nm. The relative intensity of the blue light is small, the color coordinates are(0.4531, 0.4214), and the CCT 2857 K, CRI up to 92, and the Standard deviation of color matching(SDCM) with the planckian locus less than 3. Compared the "Candle light" OLED spectra before, the OLED spectrum we designed ensure low color temperature and high color rendering with greatly improved in light color at the same time. It provides a reference for the design of OLED lighting source.3. According to the theory of Top-emitting device, we verify the tuning effect on chroma of microcavity effect, a kind of weak microcavity structure was designed to improve the chroma of new small molecule white material Pt(O^N^C^N) based on the OLED simulation software "SimOLED". The red component in the spectrum of Pt(O^N^C^N) was greatly weakened and the chroma was tuned after improvement by microcavity effect. The color coordinates of spectrum change from(0.42, 0.46) to(0.34, 0.42), close to the(0.33, 0.33). But the CRI slightly lower and changed from 78 to 75.6, we think this is due to the blue component in the spectrum is too much and it is difficult to effectively compensate by the weak microcavity effect, which leads to the CRI can not be improved.