  Solid-state cooling applications based on the electrocaloric (EC) effect are
particularly promising from a technological point of view due to their downsize
scalability and natural implementation in circuitry. However, EC effects
typically occur far from room temperature, involve materials that contain toxic
substances and require relatively large electric fields ($\sim 100$-$1000$ kV
cm$^{-1}$) that cause fateful leakage current and dielectric loss problems.
Here, we propose a possible solution to these practical issues that consists in
concertedly applying hydrostatic pressure and electric fields on lead-free
multiferroic materials. We theoretically demonstrate this strategy by
performing first-principles simulations on supertetragonal
BiFe$_{1-x}$Co$_{x}$O$_{3}$ solid solutions (BFCO). It is shown that
hydrostatic pressure, besides adjusting the occurrence of EC effects to near
room temperature, can reduce enormously the intensity of the driving electric
fields. For pressurized BFCO, we estimate a colossal room-temperature EC
strength, defined like the ratio of the adiabatic EC temperature change by the
applied electric field, of $\sim 1$ K cm kV$^{-1}$, a value that is several
orders of magnitude larger than those routinely measured in uncompressed
ferroelectrics.
