The Study on White Phosphorescent Sensitized Polymer Electroluminescence Devices
|School||Beijing Jiaotong University|
|Keywords||White organic electroluminescent Energy transfer Bilayer devices Single layer device Electroluminescent exciplex|
Abstract: Since white organic light-emitting devices (WOLED) in the field of flat panel display and solid-state light source has a unique advantage, research hotspot in recent years, while the application of organic phosphorescent material makes WOLED efficiency to achieve a leap forward. This thesis is based on WOLED especially WPLED (white polymer light-emitting device) research field analysis of the current situation and problems of the white light emitting device as a research object, designed to obtain high brightness and high-efficiency white organic electroluminescent devices. This paper first studied the doubly doped system PVK: Ir (ppy) 3: DCJTB optical and electrical properties and physical processes. Study found that there are three kinds of doped system energy transfer processes, which are the main material PVK to guest material Ir (ppy) 3, the main material PVK to DCJTB guest material objects to transfer energy and phosphorescent Ir (ppy) 3 have the energy to fluorescent DCJTB transmission, wherein the Ir (ppy) 3 to DCJTB as the main energy transfer process, and DCJTB as the dopant concentration increases. Electroluminescent process, with the increase in doping concentration DCJTB, DCJTB on the increase in the composite form excitons in Ir (ppy) 3 is formed on the composite excitons reduced, while the Ir (ppy) 3 to increase the energy transfer DCJTB , resulting in Ir (ppy) 3 of the relative fluorescence intensity decreases. Meanwhile, the Ir (ppy) 3 triplet exciton formation cross section ratio DCJTB formation of singlet excitons large cross-section, as the applied voltage increases, Ir (ppy) 3 relative luminous intensity increases. Secondly, the research system based on dual-doped PVK: Ir (ppy) 3: DCJTB dual emission layer WOLED, single emission layer WOLED and based on electroluminescent white exciplex emission characteristics of the device, was found one.) Double the device ITO / PEDOT: PSS / PVK: Ir (ppy) 3: DCJTB (100:5:0.4) / NPB (X nm) / BCP (10 nm) / Alq3 (20 nm) / Al (X = 0,5, 10,20 nm) was white, in a thickness of 5 nm NPB when optimum device performance, color coordinates of (0.31,0.39). The light emitting layer by adding an electron transport material OXD-7, the ITO \, brightness, efficiency, and stability is improved. 2) single layer device ITO / PEDOT: PSS / PVK: Ir (ppy) 3: DCJTB: NPB (100:5:0.4: X) / BCP (10 nm) / Alq3 (20nm) / Al not white. The reason is PVK, NPB → Ir (ppy) 3 → DCJTB the energy transfer process, inhibiting the blue material NPB formation of excitons, while NPB doped suppressed energy to Ir (ppy) 3 passes, causing the energy to DCJTB transmission increase, so that Ir (ppy) 3 as a light emitting dopant concentration NPB increases. 3) in the structure of ITO / PEDOT: PSS / PVK / BCP (10 nm) / Alq3 (20nm) / Al devices has been based on electroluminescence exciplex emission of white light, the applied voltage from 18V to 28V conditions , the device emitting range from (0.35,0.34) to (0.37,0.37). The device's long-wave emission from BCP excited state (LUMO) to PVK electronic ground state (HOMO) energy level transitions.