Study Of Fabrication Of Flexible White Organic Light Emitting Devices And Their Performance

Flexible organic light emitting devices(FOLED)is bending, easy to carry, lightness and broading OLED using range greatly, compared with OLED with glass underlayment, FOLED can able to bear and impingement and may come true continuing melting drum-type production. So FOLED provides the basis of realizing low cost and large-scale ,and is an important direction of the development of OLED. Recently, white organic light-emitting diodes (OLEDs) have drawn much attention due to their potential applications in full color displays, in backlight for LCDs, and in solid state lighting sources. Therefore the research and the development of Flexible white organic light emitting devices has the special significance.This paper revolved the fabrication of flexible white organic light emitting devices and enhances the efficiency and the lifetime, and we have done the following work:Firstly, We fabricate a bilayer white OLEDs with a TPD layer as a HTL and a Zn(BTZ)2 layer as both ETL and EML. White light is observed which consisting of the two parts, the one is the exciplexes emission from the interface of TPD and Zn(BTZ)2, the other one is the exciton emission from Zn(BTZ)2 layer. Its CIE coordinates is (0.33, 0.33) at 11V. We study on the effect of thickness of Zn(BTZ)2 layer on carriers recombination zone. When the thickness of Zn(BTZ)2 layer is thicker(80 nm), the electrons and holes recombine in Zn(BTZ)2 layer, when thickness of Zn(BTZ)2 layer is thinner (65nm), electrons and holes can recombine at the interface of TPD and Zn(BTZ)2 with the form of exciplexes emission, and the others recombine in the Zn(BTZ)2 layer with the from of exciton emission.In order to get higher efficient device, we have designed a device of new multi-layer structure and carried out the experiment on white light-emitting. The structure is PET/ITO/PVK:TPD/CBP:TBPe(20nm)/BAlq:Rubrene(10nm)/BCP(15nm)/Alq3(25nm)/ Mg:Ag(100nm)/ Ag(90nm). The bright and steady light emitting has been obtained,and the brightness of the devices comes to 3000cd/m2. The maximum quantum is 0.75 % . Furthermore, we attempted to use Zn(BTZ)2 as emitting materal and electron transport material. The device had a very low starting voltage at 5V. Bright white light, The brightness of white light is over 4000cd/ m2, The maximum exteral quantum efficiency reached 0.90%. The CIE coordinates of the white OLED was(0.32,0.34), which constantly located in the white-light region with changing voltage. Besides those, we also discussed the luminescence mechanisms and the capability of the devices curved.Lastly, two kinds of encapsulated material were used to envelop FOLED, and the lifetime of two kinds devices was studied and compared. Although lifetime of our enveloped devices was far less than commercial standard, it had made a remarkable progress.