The organic light-emitting device performance optimization and charge transport mechanism
|Course||Condensed Matter Physics|
|Keywords||The organic light emitting device Electroluminescent efficiency Hole pairs High Contrast Charge transport OLED Light-emitting layer The organic semiconductor An electron transport layer Electron tunneling Carrier recombination Flat panel displays Cathode material Cathode improvement Electroluminescent properties TCNQ Performance Optimization External quantum efficiency Working life Work function|
Since in 1987, a two-tier structure of organic electroluminescent devices get a good efficiency, the organic electroluminescent device is likely to become a new generation of flat panel displays, more and more researchers into the study, the paper mainly studied the optimization of the thin film structure, the carrier transport mechanism to improve the performance of the device and the device in series, as follows: 1, the high contrast of the OLED. OLED device was prepared having a low reflectance of the cathode (Black Cathode), can improve the contrast ratio of the device is at work. The cathode adopts the the optical interfering destructively principle, constituted by a semitransparent metal layer, a dielectric layer, a metal layer. In the paper C 6 0) as the dielectric layer, the device for the ambient light reflectance can be as low as about 10%. This material can use the traditional thermal evaporation growth, simple and exclude is interested Growth films for damage, addition The C 60 good electrical conductivity, although the increase of 60nm C 60 , but the operating voltage of the device did not increase, and therefore very little energy consumption in C 60 on. Cathode for low reflectivity will absorb the light emitted by the device, the article also made an attempt to use of tandem structure of the cathode improved. 2 series devices have attracted a lot of research due to its high quantum efficiency and a long working life. In this article, we have adopted a new two-tier structure, Al 2 O 3 / F 4 -TCNQ: deposition apparatus, NPB was; Al: Alq 3 / F 4 -TCNQ: NPB as a series device in the charge generation layer. Unlike has been reported that the charge generation layer of the pn junction structure, an insulator Al 2 O 3 or a hole blocking layer Al: Alq 3 sub > replace the n-type thin film. We found the F 4 -TCNQ: NPB generated holes and electrons, a hole blocking layer to help create a localized high electric field on own. This local high field can reduce F 4 -TCNQ: the NPB electron tunneling wear into the light-emitting layer barrier. 3, to study the organic electroluminescent device electrically induced the temperature dependence of the light emitting efficiency. We found NPB device current varies with temperature not play a decisive role, but the device electroluminescence efficiency variation with temperature has important implications. We found no NPB, electroluminescent device efficiency decreases monotonically with increasing temperature, the electroluminescent device efficiency when NPB first increases and then decreases with increasing temperature, we use the NPB electron blocking ability gradually decreases with increasing temperature strong to explain this phenomenon. We also found that the temperature of liquid nitrogen, with two light emitting units without charge generation layer of the current efficiency of the device can be achieved only a light-emitting single components more than twice.