Electrocaloric research through the ages

Abstract Research into electrocaloric materials has grown within the past two decades. After a brief introduction where we give a sense of this growth, we define electrocaloric effects by starting simplistically, making refinements, and including mechanistic information. We then describe the history of the field, explaining how the focus switched from bulk materials to thin films to multilayer capacitors, and how prototype coolers and measurements were pioneered. After that, we describe the current activity, which includes detailed material maps, improved metrology, and improved prototypes. Last, we comment on future directions, and the challenges that must be overcome for applications. In order for the reader to establish a holistic overview of electrocalorics, we have tended to avoid presenting chemical formulae, equations and metrics, all of which are readily available in the cited references. Graphical abstract