Study On The Performance Of Blue Fluorescent Organic Light-Emitting Diodes

Blue organic light-emitting diodes(OLEDs)provide the blue light necessary for illumination and display,so blue OLEDs have always been the focus of re-search in the these fields.Compared to blue phosphorescent OLEDs and blue th-ermally activated delayed fluorescent(TADF)OLEDs,blue fluorescent OLEDs do not have the problem of efficiency roll-off,but the performance of blue fluo-rescent OLEDs needs to be further improved.This thesis focuses on the chroma-tic stability and the efficiency improvement of blue fluorescent OLEDs.In the f-irst part of this thesis,a novel blue fluorescent material BD313 is used as the luminescent material.The chromatic stability of the device is improved by empl-oying host-guest system.In the second part of this thesis,a classic blue fluores-cent material,l-4-di-[4-(N.N-diphenyl)aMino]styryl-benzene(DSA-ph),is used as the luminescent material,which was fabricated by solution process to form the emission layer.The efficiency of the device is improved by introducing TADF exciplex host materials for the first time.1 Blue fluorescent OLEDs were constructed on a novel blue small molecule luminescent material,BD313.The chromatic stability of the device was studied and the chromatic stability of the device is improved by introducing host material.We found that with increasing the voltage,the new emission band peaking at 580 nm appears in the electroluminescence spectrum of OLEDs,which affects the device chromatic stability.This emission peak may be caused by the degradation of BD313 molecules.In order to solve this problem,the host materials,4,4?,4?-Tris(carbazol-9-y1)triphenylamine(TCTA)and 4,7-Diphenyl-1.10-phenanthroline(Bphen)are introduced on the basis of suppressing the aggregation of BD313 miolecules and balancing the carrier distribution.Thereby the chromatic stability of the device is improved.When the doping concentration of the luminescent material BD313 is 3%,the chromatic stability of the device is optimal.The applied voltage ranges from 4 V to 12 V,and the color coordinates are stable at(0.1482,0.1290).The device performance is also improved.The device luminance is increased from 301 cd/m2to 892 cd/m2,and the current efficiency is increased from 0.53 cd/A to 1.34 cd/A.2 A classic blue fluorescent material DSA-ph is used as the luminescent material and was fabricated by solution process to form the emission layer.The efficiency of the device is improved by introducing the TADF exciplex host.In this emission system,the triplet excitons generated in the exciplex materials are upconverted to the singlet state by the reverse intersystem cross.Then,the upconverted singlet excitons are transferred to the fluorescent dopant DSA-ph.The performance of the OLEDs using exciplex hosts are notably improved compared to standard OLEDs without exciplex hosts.The device luminance is increased from 2133.6 cd/m2 to 3597.6 cd/m2 and the current efficiency of device is increased from 1.44 cd/A to 3.15 cd/A.