Highly conductive and stable PEDOT:PSS films were prepared by ethylene-glycol (EG) addition and heated-stir treatment that enhanced the electric conductivity up to 1228.4 S cm⁻¹. Analysis of the long-term figure-of-merit (FoM) performances of EG-treated films with respect to variations in stirring temperatures indicated that the highest value of 78.5 was realized by the facile heated-stir treatment at 90 °C. The underlying mechanism was validated by the synergetic effect of reordering linear PEDOT chains and the effective removal of water via the supplement of thermal energy that considerably displayed the improved film conductivity based on the formation of interconnected PEDOT structures. Furthermore, via combining treated PEDOT:PSS films and Si nanowires, high-performance hybrid solar cells were realized. This was accomplished by reduced charge-transfer resistance and sound heterojunction characteristics that facilitated the charge separation and eventual charge collection by the electrode, thus contributing to the enhancement efficiency. The optimal heated-stir treatment at 90 °C led to improved cell conversion efficiency achieving 12.2%, which was 1.3 times higher than the result based on the conventional room-temperature process.