Thickness dependence of electrocaloric response in ferroelectric thin films

•The influence of film thickness on electrocaloric (EC) is precisely determined.•EC strength described by (ΔT/Δε) decreases as the film’s thickness decreases,•EC strength increases when decreasing the thickness in the thinnest films.•Values of EC response for BST films are higher than values measured for BTO films. The first-principles-derived approach combined with the Wang-Landau algorithm is used to precisely determine the thickness dependence of the ferroelectric and electrocaloric (EC) effect response in stress-free (Ba0.50Sr0.50)TiO3 thin films under ideal short-circuit electrical boundary conditions. The results indicate that as the film’s thickness decreases, the polarization, transition temperature, and diffuseness character of the phase transition are enhanced, while the maximum value of the specific heat occurring near the transition temperature increases when the film thickness increases. The calculations also reveal that the EC strength described by ΔT/Δε in the thinnest-studied BST films increases when decreasing the thickness of the films, while this response decreases as the film’s thickness decreases in the thickest-investigated BST film. At room temperature, the calculated values of the EC response for BST films are higher than values measured for BTO films.