Fabrication And Properties Of Flexible Organic Light-emitting Devices Based On Graphene

Organic light emitting devices(OLED)are in widespread use in display and illumination devices due to their intrinsic characteristics such as high luminous efficiency,mechanical flexibility,ease of fabrication and lower cost of material.Graphene has great potential as the anode of OLED because of its high carrier mobility,good transmittance and excellent mechanical properties.However,there are still some issues,such as low work function,surface roughness and resistance.We attempts to use two methods to modify graphene anode to overcome the disadvantages and study on device performance.So the main investigations of this article are as follows:Firstly,the effect of chemical doping and surface modification on graphene films were studied.Transmittance of Chemical doped graphene films remained unchanged and the surface resistancewas reduced by 68%.A layer of organic polymer PEDOT:PSS film was spray coated on the surface of graphene films to optimize its surface properties,and graphene/PEDOT:PSS composite films had sheet resistance of 140 ?/?,average transmittance of 78%,and maintained stable conductivity during multiples bending test.On the other hand,a layer of inorganic oxide MoO3 was vapor-deposited to modify graphene film,and the composite films exhibited the transmittance of 80%and small surface roughness.Subsequently,the solution-processed blue FOLEDs with graphene/PEDOT:PSS-based conductive films was fabricated.The device structure was PET/Graphene/PEDOT:PSS/PFO/ZnO/Al.The preparation and performance of the PFO and the ZnO layers were studied.The effect of spin coating speed about ZnO layer on device performance was discussed,and the results indicated that device had a better performance at 3000 rpm whose turn-on voltage was 3 V.The maximal current efficiency of the flexible device is 0.51 cd/A and CIE color space for the OLEDs was(0.17,0.17).Besides,the EL spectra of the device kept pace with PL spectra of PFO.Finally,the evaporated green FOLEDs with graphene/MoO3-based composite films was prepared.The device structure was PET/Graphene/MoO3/TAPC/TCTA:Ir(ppy)3/TPBi:Ir(ppy)3/TPBi/LiF/A1.The effect of the thickness of MoO3 layer,the light-emitting layer and the transport layer on performance were investigated.It was indicated that maximal current efficiency of the double emissive layer device was 1.02 cd/A at a CIE 1931 chromaticity of(0.37,0.59)and the turn-on voltage was 3 V.Besides,the device did not exist offset phenomenon under different emission peak voltage.In conclusion,flexible OLEDs were fabricated successfully by surface modification of graphene films and optimization on preparation.This study provides some practical basis for preparation and structural design of flexible OLEDs based on graphene anode.