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Nanosphere Templated Continuous PEDOT:PSS Films with Low Percolation Threshold for Application in Efficient Polymer Solar Cells

Seminar Group: 


Bumjoon J. Kim


Department of Chemical and Biomolecular Engineering
Korea Advanced Institute of Science & Technology


Friday, March 15, 2013 - 4:00pm


ESB 1001


Profs. Ed Kramer and Craig Hawker

Self-assembled monodisperse spheres can be used as templates for the production of continuous conducting polymer phases with low percolation thresholds. In this work, nanometer-sized monodisperse polystyrene nanospheres (PS NS) were designed as an opal template for the formation of three-dimensionally continuous poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. The resultant films were successfully applied as the anode buffer layer (ABL) to produce efficient polymer solar cells (PSCs) with enhanced stability. The effect of the PS NS template on the PS NS-PEDOT:PSS film (PS NS-PEDOT:PSS) was thoroughly examined regarding the morphological and electrical behavior as a function of the PS NS volume fraction (φPS). The conductivity of the PS NS-PEDOT:PSS films was maintained up to φPS=0.75-0.80, which indicates that the percolation threshold of the continuous PEDOT:PSS layer in the film was as low as 0.20-0.25. This value is in good agreement with the void volume fraction in the film of hexagonally close packed spheres, indicating that the formation of continuous PEDOT:PSS films using PS NS templates was successful. The photovoltaic performances of both PSCs were maintained up to φPS=0.8. In addition, the use of a reduced amount of PEDOT:PSS polymer in the ABL dramatically enhanced the air stability of the PSCs compared to the device containing a pure PEDOT:PSS ABL. This approach provides a methodology to produce semiconducting blends that are processable as both films and bulk samples and that combine electrical conductivity with enhanced stability.