Nondoped Carrier Generation Unit And Its Tandem And Inverted Organic Light-emitting Diode

Organic Light-Emitting Devices(OLEDs)have attracted wide attention in academia and industry due to their low driving voltage,high efficiency and flexibility.It is promising to be the third generation display technology following the flat panel display and solid-state lighting.However,when it comes to the industrial production,there are some nuts in the traditional OLED,such as the lower luminance and shorter lifetime.Due to these problems,the study of tandem Organic Light-Emitting Device and inverted Organic Light-Emitting Device have been favored by more and more researchers in recent years.However,most of the existing carrier generation layers are doped,the preparation process is complex,the repeatability is poor,the driving voltage is high,and the electron injection layer of IOLED depends on the work function of cathode barrier.To solve these problems,we proposes the undoped carrier generation layer,and applies it to the tandem and inverted OLED to achieve the purpose of high efficiency.1?We propose to use undoped LiF/AL/HAT-CN as carrier generation layer and use FIrpic as phosphorescent dye and prepare laminated blue phosphorescence device and white light device by evaporation.The generation process and mechanism of carrier are analyzed.The thickness of AL in the middle layer is optimized by combining its transmissivity and C-V characteristics.It is concluded that when the thickness of AL is 5nm,the performance of the device is optimal.Compared with conventional devices,the current efficiency of the blue device and white device is 53.1 cd/A and 94.9 cd/A respectively,which is 2.1 times and 1.9 times of that of single-layer devices.Compared with the doped carrier generation layer,Li F/AL/HAT-CN has the advantages of simple preparation,high repeatability and higher efficiency,which provides a demand for future commercial production.2?In order to obtain the optimal device structure,we replace the HAT-CN in the carrier generation layer(Li F/AL/HAT-CN)with Mo O3,and use Li F/AL/Mo O3 as the connection layer to prepare the blue phosphorescence device by the evaporation method.Then the organic material Liq is used to avoid the influence on the device performance caused by the high evaporation temperature of the inorganic material Li F.The thickness of the interconnect layer Liq/AL/HAT-CN is optimized again and the influence of the thickness of the interconnect layer on the device performance is analyzed.From the experimental results,we find that when the thickness of Liq is 3.5 nm,the current efficiency of the laminated blue light devices reaches 48.5 cd/ A,which is greatly improved compared with the conventional devices.3?Based on the charge generation ability of the undoped carrier generation layer(Li F/AL/HATCN),we apply it to the inverted structure.In the inverted structure,the HAT-CN/AL/Li F is used as the electron injection layer and the appropriate device structure is designed in combination with the charge generation mechanism,and the inverted fluorescence device with good performance is fabricated.At the same time,we have prepared doped and undoped blue phosphorescence devices using this electron injection layer.The current efficiency of doped inverted blue phosphorescence OLED can reach 29.4 cd/ A.Compared with common inverted devices,the undoped phosphorescence devices don't depend on the work function of the cathode,improve the stability of the device and promote the industrial production in the future.