Improving Luminescent Properties Of Organic Molecules Based On Ag Nanostructures And Molecular Orientation

Organic light-emitting diodes(OLEDs)have the advantages of self-illumination,wide viewing angle,light weight,many kinds of materials and low energy consumption.With the rapid development of OLEDs technology,it has gradually reached the level of commercial application in solid lighting,display etc.The mature development of OLEDs makes people full of hope for realizing the goal of electrically pumped organic solid-state lasers.In this paper,the surface plasma resonance(SPR)effect of silver nanostructures is used to enhance the performance of OLED devices and amplified spontaneous emission(ASE)of organic gain medium.Photoluminescence(PL)and ASE of BUBD-1,an organic gain medium,were optimized by controlling SPR and molecular orientation.The main contents of this paper are as follows:Section ?: The PEDOT:PSS:GO/Ag NWs were prepared composite electrodes by solution-processed spin-coating.Their respective advantages can be comprehensively utilized and the disadvantages of materials can be avoided to a certain extent.The parameters of composite electrode are superior that the sheet square resistance is 17 ?/sq and the transmittance at wavelength of 550 nm is 88.7%.The photoelectric properties of OLED devices were prepared on the composite electrode that is superior to OLED device performance based on ITO.The research show that the reasons for the improvement about performance of OLED device with the composite electrode,one is that the electrode itself has superior electrode performance that almost comparable to ITO,and the other is that the silver nanowires in the electrode will increase the optical coupling output and cause far-field SPR effect.Section ?: The effect of substrate temperature on the luminescence properties BUBD-1 films prepared by vacuum thermal evaporation method was studied.The PL intensity of BUBD-1 film decreased at first with the increase of substrate temperature,and reached the lowest intensity at the substrate temperature of 75 ?.Then the PL intensity increased with the increasing substrate temperature.While the trend of ASE characteristics with substrate temperature is opposite to that of PL intensity.The optimized ASE threshold is reduced by70% to 3.5?J/pulse at the substrate temperature of 75 ? comparing to the reference sample.It shows that the molecular orientation of BUBD-1 thin film has a great influence on its luminescence properties.The molecular orientation changes with the substrate temperature.When the substrate temperature was 75 ?,the vertical molecular orientations accounted for the largest proportion.It indicates that the vertical molecular orientation is favorable to the side emission(ASE)of the BUBD-1 film,while the horizontal molecular orientations are favorable to the bottom emission of the BUBD-1 film.Section ?: At first,the influence of silver island film's thickness on the luminescence properties of BUBD-1 films prepared by solution-processed spin-coating was studied.It is found that the surface plasma resonance(SPR)effect of the silver island film enhanced the luminescence properties of BUBD-1 film.And when the thickness of Silver island film is2 nm,BUBD-1 films had the best luminescence enhancement effect,and the luminescence intensity increased by nearly 12 times,the ASE threshold decreased by 34%,and the ASE gain was by 1.74 times.Secondly,the effect of the location of the silver island film on the luminescent properties of BUBD-1 film was studied.It is found that different locations of silver island films have different enhancement effects on ASE properties of BUBD-1 films.Finally,based on the effect of luminescent properties of organic films by silver island films,OLED devices were fabricated by vacuum evaporation and solution-processed spin-coating,respectively.It was found that the silver island can enhance the photoelectric performance of OLED devices fabricated by both of two methods.The reason is that the surface plasmon of silver nanoparticles can not only enhance the photoluminescence of the organic film,but also enhance the light scattering effect in the device and enhance the output coupling efficiency.