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)I-3 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 (Delta T) of 8.41 K at 30 MV m(-1) and electrocaloric strength (Delta T/Delta E) of 0.63 K m MV-1 at 10 MV m(-1), respectively. The prominent electrocaloric effects of MDABCO(NH4)I-3 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 degrees domain walls form in the [MDABCO](NH4)I-3 bulk, which is consistent with the experimental results. This work not only provides new insights into organic perovskite [MDABCO](NH4)I-3, but also guides for further developing to realize remarkable room-temperature electrocaloric cooling.