A Study Of The Influence Of Charge Genereation Layer Thickness Ontandem White OLED

Due to the development of materials and device architectures,white organic light-emitting diodes(OLEDs)are being considered as efficient solid-state lighting sources in display and lighting application.White OLEDs offer excellent properties such as higher power efficiency,more than fluorescent lamps and inorganic LEDs,thin and shape changeable,glare-free.It can be applied as not only solid state light source,but also flat panel display working together with color filter.These attractive characteristics have drawn OLEDs a lot of attention.Tandem white OLEDs contain a set of light emitting units with different regions of the spectrum,which are connected vertically in series with charge generation layer(CGL).Under an electric field,holes and electrons generated in CGL inject in to the adjacent emitting units,and then recombine with electrons from the cathode side and holes from anode side.The current efficiency scale linearly with the number of stacked electroluminescent units.In addition,under same initial luminance,tandem white OLEDs have longer lifetimes than conventional white OLEDs.In this study,we have fabricated a set of tandem white OLEDs by using a new CGL,which combines a p-doped hole transporting layer(HTL)with an electron extraction layer(EEL).In this CGL,holes and electrons are generated in p-doped layer,and the EEL assists electron tunneling into the adjacent electron transport layer.It is found that the CGL has high efficiency,high transparency and high stability,and furthermore,it has a high conductivity,which makes it possible to optimize the structure and adjust the color of the device by changing the thickness of the layer,but without affecting the electrical characteristics of the device.Compared with conventional white OLEDs,this tandem white OLED has simple process,high efficiency and high stability.It is expected that this tandem white OLED can be widely used in future display and lighting applications.