The Wet Method Process Manufacture And Research Based On The Polyfluorene Polymer Light-emitting Devices

Polymer light-emitting devices (PLED), which have the advantages of processable, low cost, easily to realize large-area and flexible display, have received more and more attentions, However, compared with inorganic LED and organic-small-molecule devices, the manufacture processes of PLED, especially spin-coating is an important challenge.Therefore, the PLEDs were fabricated by spin-coating technology and using blue-light emission of polyfluorene (PF) as light-emitting layer. The efficiency of PLED were investigated in detail. Ultimately, the solution-process technology of PLEDs was studied. As follow:The effects of spin-coating and heat-treatment parameters on the propertied of PLEDs were discussed. Firstly, the optimum process parameters of organic functional layers were obtained by orthogonal experiment and atomic force microscopy (AFM) images. The best parameters for hole-transport layer (HTL) PEDOT:PSS are concentration of1%(mass fraction),3drops solution and spining for40s at the rate of3000r/min, respectively; Meanwhile, The best parameters for organic light-emitting layer (EML) of PF are concentration of10mg/ml,6drops solution and spining for40s at the rate of1500r/min; The devices were heated to100℃by vacuum sublimation for15min. The optimum parameters were verified further.PLEDs were prepared by employing4,7-Bithiophene-2,1,3-benzothiadiazo-le (DBT) blended in PF with different proportion and a new polymer polyfluorene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole (PF-DBT) as light emitt-ing materials, respectively. There is an effective energy-transfer process from PF units to DBT units in based-on PF-DBT devices The PF:DBT devices with lower DBT concentration show lower turn-on voltage and higher luminance. The properties of based-on PF-DBT inferior to the devices of PF:DBT.The PLED devices with the structure of ITO/PEDOT:PSS/EML/Ca/Al were fabricated by using red-light4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) blended in PF with different proportion as EML. The results indicated that the emission color change from blue to red with the blended proportion of DCJTB at1%-20%. The near white light was observed at a proportion of2%with high efficiency and luminance.Finally, the device of ITO/PEDOT:PSS/PF/Cs2CO3/Ag was fabricated by solution-process technology. Screen printing method was employed to prepared electrode Ag by using conduction silver liquid instead of traditional vacuum evaporation. Optimized devices using Cs2CO3/Ag as cathode have better performances with high efficiency.