Towards electrocaloric heat pump - A relaxor ferroelectric polymer exhibiting large electrocaloric response at low electric field

A polymer that generates large cooling under applied voltage is attractive for many applications. The past decade has witnessed the discovery and advancement in electrocaloric (EC) polymers, which display large electric field induced temperature and entropy changes. However, in contrast to the burgeoning literature on large electrocaloric effects (ECEs) in various ferroelectric materials, there are no EC devices employing these EC polymers, demonstrating a meaningful cooling power. Here, we show that it is the dielectric breakdown, the weakest link problem, in EC materials which poses a critical barrier for transitioning these advanced EC materials to practical EC coolers. Hence, high quality EC films and high performance of EC materials, exhibiting large ECE at low electric fields, are required to overcome this barrier. Here, we show that by expanding the compositions in EC polymers, a relaxor tetrapolymer exhibits a critical end point at low electric fields, leading to large ECE induced at low electric fields.