Studies On Factors Impacting The Luminance Of Organic Electrophosphorescent Devices

Compared to organic electrofluorescent devices,electrophosphorescent devices have more extensive applications in future.Therefore,the latest focus for organic light-emitting devices(OLED)is electrophosphorescence.Based on the challenges in electrophosphorescent devices,this paper consists of four aspects:the impacting of different hosts on the luminance of electrophosphorescent devices;the sensitizing and the energy transfer from phosphorescent materials to fluorescent materials in light-emitting layer;the influence of electron-transporting materials doped in light-emitting layer with different concentrations on the luminance of the device;the influence of evaporation conditions of hole-blocking layer BCP and electron-transporting layer Alq₃ on the performance of emitting system.This paper consists of five chapters.In chapter one,the summary of organic light-emitting devices is introduced.Chapter two is aimed at the mechanism and the focus of the electrophosphorescent devices.The following three chapters study the mentioned four aspects by experiments and theory.Chapter six is the conclusion.(1)Host-guest system is always used in the light-emitting layer of organic electrophosphorescent devices,and energy transfer from host to guest improves the luminance of phosphorescent materials.Therefore,choosing appropriate host materials is one of the useful ways to improve the performance of organic electrophosphorescent devices.·Different devices with phosphorescent material tris(2-phenylpyridine)iridium [Ir(ppy)₃]doped in two kinds of hosts are constructed in this paper.Respectively,the two kinds of hosts are polyvinylcarbazole[PVK]and 4,4'-N,N-dicarbazole-biphenyl [CBP].The properties of energy transfer between host materials and dopants are studied, and the influences of different hosts on the luminance of devices are compared.(2)Based on(1),the devices with fluorescent material 5,6,11,12,-tetraphe-nylnaphthacene[Rubrene]and phosphorescent material[Ir(ppy)3]both doped in host are constructed,The energy transfer in the light-emitting layer With host and two dopants is studied and the sensitizing of Ir(ppy)₃ to Rubrene is confirmed.In addition, we have compared the different sensitizing effects in the two hosts.(3)The effects of electron-transporting materials PBD doped in light-emitting layer with different concentration on the luminescence properties are investigated.Through the analysis of these devices,we find that the brightness of these devices codoped with PBD is improved.(4)Many efforts focus on the effect of the preparation conditions of organic materials on the performance of the devices recently.In this paper,we study the influence of evaporation conditions of hole-blocking layer BCP and electron-transporting Alq₃ layer on the performance of the light-emitting system.