Giant room temperature elastocaloric effect in metal-free thin-film perovskites

Solid-state refrigeration which is environmentally benign has attracted considerable attention. Mechanocaloric materials, in which phase transitions can be induced by mechanical stresses, represent one of the most promising types of solid-state caloric materials. Here, we develop a thermodynamic phenomenological model and predict extraordinarily large elastocaloric strengths for (111)-oriented metal-free perovskite ferroelectric [MDABCO](NH4)13 thin films. The predicted room-temperature isothermal elastocaloric ΔSc/Δσ and adiabatic ΔTad/Δσ for [MDABCO](NH4)13 are 60.0 J K−1 kg−1 GPa−1 and 17.9 K GPa−1, respectively, about 20 times higher than traditional ferroelectric oxides such as BaTiO3 thin films. We also demonstrate that the elastocaloric performance can be improved by reducing the Young’s modulus or enhancing the thermal expansion coefficient (e.g., via chemical doping). These discoveries may spur further interest in metal-free organic ferroelectrics for next-generation elastocaloric refrigeration devices.