White Organic Light-emitting Devices Based On Double-doped Organic Crystals

For nearly two decades,organic light-emitting devices(OLEDs)have attracted much attention among academia and manufacturing due to their outstanding advantages,such as,wide viewing angle,energy saving,large amount of material sources,environmental protection,light weight and large size flexible bending display.It had been called one of the most promising high-tech fields in the new century.After intensive research by researchers in various countries,OLEDs have undergone rapid development and now occupies an important position in the display and lighting consumer market,which has basically shifted from the experimental stage to the product-oriented stage.Among these,white OLEDs(WOLEDs)are particularly important.Generally speaking,their applications cover lighting,LCD backlights,special light sources,and so on.As a light source,WOLEDs show great potential applications.In particular,the ultra-thin and transparent WOLEDs with high color rendering index(CRI)are attracting the attention of the next generation of ideal lighting sources.In general,for WOLEDs,the white light is formed by a mixture of three primary colors of red,green and blue(RGB)or two primary colors of blue and yellow(ie,a plurality of light-emitting layers emit light simultaneously).However,the fabrication process of the device of these structures are slightly complicated and increase the cost,on the other hand,the color rendering index of the BY white device is generally lower than 70,which does not meet the performance requirement of the actual lighting source.To date,most WOLEDs devices have been made from fluorescent and phosphorescent small molecule,polymer amorphous materials.The existence of their own molecular arrangement of disorder,high impurity content and low carrier mobility defects severely limited the development of high efficiency,low power WOLEDs.As a result,researchers have sought to replace the traditional light-emitting materials,a new type of semiconductor optoelectronic functional material-organic crystals.In contrast,organic semiconducting crystalline molecules are highly ordered within the molecule and have fewer impurity content and fewer defects,resulting in higher carrier mobility than amorphous materials.This determines its important application value in the fields of OLEDs,organic semiconductor lasers and the field effect transistors.Pope et al had demonstrated electroluminescent devices using anthracene crystal materials for the first time,and successfully opened up the development path of OLEDs based on organic crystalline semiconductor materials.And after people's continuous efforts,in recent years,reports on the preparation of light-emitting diode devices based on organic crystalline semiconductor materials have also been published.Therefore,in this paper,we introduce the preparation of organic crystal-based white light-emitting diode devices through the doping method.In this method,we take BSB-Me blue crystal material as the host,which doped with tetracene and pentacene as the green and red dopants in turn.There existing the F?rster energy transfer process between host and two guest molecular materials in such a double-doped system.By adjusting the doping ratio of two kinds of guest molecular materials,the fluorescence peaks of the host materials and the guest materials are close to each other,thereby achieving uniform white light emission.Compared with the conventional white light devices based on two light-emitting layer or multi-light-emitting layer,the light-emitting layer of our devices is a single doped crystal material,which indicating a more simple device structure and a relatively easy preparation process.In addition,the three-color-strategy WOLEDs can achieve high color rendering index.