A novel PEDOT:PSS/SWCNH bilayer thin film counter electrode for efficient dye-sensitized solar cells

Thin platinum deposited over fluorine-doped tin oxide glass substrate is a well-known and widely used counter electrode for efficient dye-sensitized solar cells. In this paper, we investigated a potential and Pt-free bilayer thin film counter electrode based on single wall carbon nanohorn over PEDOT:PSS film. The bilayer thin film counter electrode was developed using a simple spin coat process. The results of atomic force microscope and scanning electron microscope unveil the uniform distribution of single wall carbon nanohorns over PEDOT:PSS with average size of 76 nm. The extensive electrochemical analysis demonstrated superior electrocatalytic behavior for bilayer counter electrode with lower peak-to-peak separation potential of 0.6 V, lower Rs and R_CT values of 25.9 Ω and 399 Ω, and higher J_o value of 2.4 mA cm⁻². The fabricated DSSC using bilayer counter electrode witnessed higher power conversion efficiency of 5.1%, compared to PEDOT:PSS (3.87%) and SWCNH (1.88%), and is almost equivalent to the platinum-based counter electrode (5.53%). The present study of bilayer counter electrode has great potential in terms of low-cost and non-platinum counter electrode for dye-sensitized solar cell applications.