Study On The Performance Of Host-guest Doped OLED Devices Based On TADF

Organic Light-Emitting Diode(OLED)with its self-luminous,full-color display,high brightness,high contrast,low voltage drive,low power consumption,thin and light shape,flexible,high luminous efficiency,fast response,Wide viewing angle and other excellent characteristics,has become a popular research direction in the field of lighting and display.With the development of scientific research technology,researchers have developed the third generation of OLED luminescent materials-Thermally Activated Delayed Fluorescence(TADF)materials,TADF materials have also been widely used in OLED devices,However,TADF OLED devices still face problems such as efficiency and longevity,and there is still room for development in these areas.In order to solve the above-mentioned problems of TADF OLED devices,this paper mainly studies the performance and luminescence mechanism of TADF OLED devices doped with TADF materials.By optimizing the doping ratio of the host and guest materials in the light-emitting layer of the device,the introduction of auxiliary dopants achieves The purpose of improving the performance of TADF OLED devices.The specific content of the study can be divided into the following three parts:First,CBP as the host material of the light-emitting layer,TADF material4Cz IPN as the guest material of the light-emitting layer.This chapter systematically explores the effect of the change in the dopant material concentration of the TADF OLED light-emitting layer guest on its light-emitting performance.By optimizing the doping concentration of the guest,the optimal device with the doping concentration of4Cz IPN of the guest material of 8wt%was obtained.It have a low start-up voltage of3V,a maximum luminous brightness of 20700 cd/m2,a maximum external quantum efficiency of 11.54%,a maximum power efficiency of 16.22 lm/W,and a maximum current efficiency of 36.14 cd/A.Combined with the EL spectrum of the device without doping concentration,it is obtained that the energy transfer is the main luminescence mechanism when the doping ratio is less than 8wt%,and when it is higher than 8wt%,the carrier capture luminescence mechanism begins to dominate.These tasks It also provides a basis for the subsequent experiments on efficiency and life span during the period.Then,on the basis of determining the optimal doping ratio of 4Cz IPN 8wt%,the effect of the mixed host doping system of the light emitting layer and the carrier modulation layer on the performance of the OLED device was studied.Compared with the traditional single host OLED device,the device's Co-evaporation of TPBi and CBP was added to the luminescent layer as a mixed host.Design experiments were made to prepare comparative devices with different concentration ratios of the mixed body.Through the curve analysis of the current density and luminescence brightness of the devices with different concentration ratios of the mixed body,the mixed host material CBP:TPBi The ratio=1:1,add a layer of 10nm CBP carrier modulation layer,the device under the combined effect of the two achieves a low start voltage of 3V and a maximum luminous brightness of 51500 cd/m~2,and the maximum EQE of the device Reached 23.93%.When TPBi is added to the light-emitting layer,the charge transport of the device is more balanced,which in turn improves the light-emitting brightness.Through the analysis of the photoelectric performance of the device,the CBP carrier modulation layer can block electrons and limit the carrier recombination center in the light-emitting layer,which is an important reason for the improvement of the efficiency and brightness of the device.Finally,This part of the content systematically studies the effect of the hole transport layer in the device structure on the life of the OLED device,and explores the difference in the improvement of the device life of different hole transport layer materials and the doping concentration of the phosphorescent dopant in the light-emitting layer,doping the luminescent layer of the device with different concentrations of Hex-Ir(phq)2(acac).When the phosphorescent dopant concentration in the luminescent layer is 7.5%,the T80 of the device reaches 191.29 h and the maximum brightness also reaches 47238 cd/m~2.In the same way,the EL spectrum analysis of the device under different voltages shows that Hex-Ir(phq)2(acac)is used as a luminescent material,and 4Cz IPN is used as an energy transfer intermediate medium to promote energy transfer.As a hole transport layer,TAPC can help to improve the life of the device.The introduction of phosphorescent materials reduces the aggregation of triplet excitons,avoids the occurrence of TTA phenomenon,and improves the lifetime.