DEVELOPMENT OF NANO-THIN FILMS OF CONDUCTIVE POLYMERS BY USING POLY(VINYL ALCOHOL) AND SPIN-COATING FOR ORGANIC SOLAR CELL APPLICATIONS

Abstract

The integration of polymer blending and doping concepts to improve various properties of poly(3,4-ethylene dioxy thiophene) poly(styrene sulfonate) (PEDOT:PSS) nano-thin films were applied. According to the polymer blending concept, at 0.08 wt. %PVA, it could bring the conductivity of the blends to reach a maximum conductivity of 1.18 S/cm, and also could provide a good contact angle of 8.8o. The films transmission decreased with increasing PVA content; however, all specimens still showed excellent transmittance values of more than 80 %. The thermal stability and the resistance to abrasion of the nano-thin films were improved by strong covalent bonds between PVA and PSS. Use of the doping agent, quinoxaline, was aimed to particularly enhance the conductivity of PEDOT:PSS. The highest conductivity (2.75 S/cm) was achieved when 0.5 wt% quinoxaline was added into 0.08 wt% PVA/PEDOT:PSS while the other properties were not significantly altered. Poly(3,4-ethylenedioxythiophene): sulfonated polyimide (PEDOT:SPI) nano-thin films were successfully developed by the addition of anionic surfactant and poly(vinyl alcohol) (PVA). Sodium dodecyl sulfate (SDS) surfactant was introduced to improve the dispersion stability of the PEDOT:SPI particles in water. The highest conductivity was properly achieved at 0.08 wt. %PVA in PEDOT:SPI2/SDS/PVA film. In addition, PVA also improved the thermal stability of the conductive films. All of the conducting thin films showed a high transparency of more than 85% transmission. The interactions between conducting polymers, PVA, and SDS surfactant are the key factor to improve nano-thin film properties. Moreover, the interactions between SDS and SPI were proven to be different from those of between SDS and PSS in conventional PEDOT:PSS solutions.