Unleashing the power of giant negative electrocaloric effect through heterojunctions

The compact, integrated solid-state refrigeration using the electrocaloric effect (EC) has gained wide interest in electronics, healthcare, and defense sectors for its low power consumption. Despite rising interest, existing electrocaloric refrigeration materials typically face challenges including low efficiency and complex heat transfer dynamics. Here, we present a novel approach to achieve high cooling efficiency within a single electric field cycle via positive-negative electrocaloric synergy effects. A high-performance conversion of positive EC effect (ΔT_max ∼ 7.54 K) to negative EC effect (ΔT_max ∼ −11.85 K) over a wide temperature range (303 ∼ 443 K) is exampled in sandwich heterojunction-thin-film structure of Ca_0.2Zr_0.8O_1.8/85 %Pb(Mg_1/3Nb_2/3)O₃-15 %PbTiO₃/Ca_0.2Zr_0.8O_1.8. This linear dielectric dead layer of Ca_0.2Zr_0.8O_1.8 aids in the polarization reversal of pinned domains at the interfaces and promotes the emergence of polar nanodomains within this dead layer, enabling the leveraging of positive and negative EC synergy effects in a single electric field cycle. Our study enriches the functionalities of heterostructure interface, offering a distinctive approach to realize high-performance chip level electrocaloric films.