Designed Giant Room-Temperature Electrocaloric Effects in Metal-Free Organic Perovskite [MDABCO](NH₄)I₃ by Phase–Field Simulations

Achieving a colossal room-temperature electrocaloric effect is essential for practical solid-state refrigeration applications with low-cost and high-efficiency. Here, through the design of applying external stimuli (hydrostatic pressure and misfit strain), giant room-temperature electrocaloric effects in the bulk and thin film of metal-free organic perovskite [MDABCO](NH₄)I₃ are obtained by using a combination of thermodynamic calculations and phase–field simulations. Under the hydrostatic pressure of 1 GPa, there emerges excellent room-temperature (300 K) electrocaloric performance with the temperature change (ΔT) of 8.41 K at 30 MV m⁻¹ and electrocaloric strength (ΔT/ΔE) of 0.63 K m MV⁻¹ at 10 MV m⁻¹, respectively. The prominent electrocaloric effects of MDABCO(NH₄)I₃ may be related to its rapid change rates of free energy barrier height. Additionally, it can be found that some stripe domains and non-180° domain walls form in the [MDABCO](NH₄)I₃ bulk, which is consistent with the experimental results. This work not only provides new insights into organic perovskite [MDABCO](NH₄)I₃, but also guides for further developing to realize remarkable room-temperature electrocaloric cooling.