Effect of Ag-doping on crystal structure and high temperature thermoelectric properties of c-axis oriented Ca3Co4O9 thin films by pulsed laser deposition

► Ag-doped c-axis oriented Ca3Co4O9 thin films have been prepared by pulsed laser deposition. ► Ag substitution limit at Ca site is found to be ∼5 at% and heavy Ag-doping results in composite structure. ► Ag-substitution increases carrier concentration and mobility; while Ag-compositing greatly reduces Seebeck coefficient. ► Power factor reaches ∼0.73 mW m−1 K−2, which is about 16% improvement.