| Over the last years, PEDOT:PSS attracted a great attention for its applicability in the field of organic electronics like organic field-effect transistor, organic light emitting diode, organic solar cell, and organic resistance random access memory et al. due to its attractive properties:high stability, high conductivity, high transparency, flexibility, low weight et al.The pattern method is the key step to forming the electronic devices for it will influence the performance, integrated density and cost of the device. However, PEDOT.PSS is not amenable to conventional silicon semiconductor processing methods because of its properties are totally different from the silicon semiconductor. In the past decade, many techniques such as micro contact printing, inkjet printing have been developed to pattern organic electronic devices, but each has limitations. For example, micro contact printing needs the use of rubber molds, which are distorted by the organic solvent.In this paper, we will use the Nanoimprint lithography to fabricate ordered 2D or 3D Micro/Nano structures because this pattern method is a high output and low cost technique. The biggest challenge to pattern the PEDOT:PSS by Nanoimprint lithography is that PEDOT:PSS is non-thermoplastic with mechanical properties changing very little from 25 to 200℃. We add some amount of glycerol into PEDOT:PSS so that the thin film will be softened. We use a series of process parameters to fabricate miro/nano patterns, and find the key parameter is the bake time. We also develop a model to explain what role the glycerol played during imprinting. At last, we successfully fabricate grating with width of 600nm, height of 90nm, period of 1.2um and hexagon pores with diameter of 600nm, depth of about 95nm period of 1.2um on the surface of PEDOT:PSS thin film.We also test the patterned PEDOT:PSS thin film by XRD and Raman. It shows that the polymer backbones in the PEDOT:PSS imprinted films do not exhibit any preferred in-plane orientation along or perpendicular to the grating direction in contrast to the Nanoimprinted semiconducting polymers like P3HT. What is more, we test the conductivity of Nanoimprinted films by Al/PEDOT:PSS/Al structure. It shows there is no change of conductivity after Nanaimprinting. Still, it is useful to fabricate Mico/Nano patterns on the surface of PEDOT:PSS since it will increase the scattering effect, which will be helpful to increase the transfer efficiency of organic solar cell and the luminescent efficiency of organic light emitting diode. Finally, we test the contact angle of the films. It shows Nanoimprinting will increase the surface energy and lower the contact angle, which will be helpful when spin-coating other materials on top of PEDOT:PSS.The second most important part of this paper is fabricating PEDOT:PSS/PVP Nano-fibers by electro-spinning. 1D Nanomaterials attracted great attention for its remarkable characteristics:very high porosity, very large surface area to volume ratio. We dissolve a proper amount of PEDOT:PSS and PVP in DMF, and try different process parameters to electro-spun PEDOT:PSS/PVP nano-fibers. We find the applied voltage is a very important parameter. It should be higher than 18KV so that we can get separated PEDOT:PSS/PVP nano-fibers. We test the PEDOT.PSS/PVP nano-fibers by Raman, it shows both PEDOT:PSS and PVP are left in Nano-fibers. We also proved the dried process is necessary so that the Nano-fibers can be kept for longer.At last, we made a gas sensor by PEDOT:PSS/PVP Nano-fibers thin film. We electrospun amount of PEDOT:PSS/PVP Nano-fibers on top of A1 finger electrodes. And then test the change of resistance of the thin film when it is exposed in THF gas. I-V test shows this gas sensor is very sensible to THF gas.Generally speaking, we successfully fabricated ordered 2D and 3D structures on PEDOT:PSS thin film and 1D disordered Nano-fibers structure of PEDOT:PSS/PVP. Those processes will be very useful to fabricate organic devices. |
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