Large electrocaloric strength in ferroelectric nematic liquid crystals with a tuneable operational temperature range

Abstract

The electrocaloric (EC) effect offers a promising energy-efficient and clean cooling technology. We present the first direct measurements of EC temperature change in a new family of EC fluids, ferroelectric nematic liquid crystals (FNLCs), demonstrating in two such materials temperature jumps of $|\Delta T_j|$ ~ 0.2 K for field changes as low as $\Delta E$ ~ 0.1 $V\mu m^{-1}$. Indirect measurements of adiabatic temperature change $|\Delta T|$ confirm that these direct measurements are an underestimate and that $\Delta E$ = 2 $V\mu m^{-1}$ can induce up to $|\Delta T|$ ~ 1.6 K, yielding EC strengths $|\Delta T/\Delta E|$ up to 100% higher than incumbent materials. For temperature spans of 5-10 K, we predict a coefficient of performance of ~21-40. We find $|\Delta T|$ ~ 1 K for >100 FNLCs that collectively span all temperatures between $0{}^{\circ }$C and $100{}^{\circ }$C. This, together with the new device concepts conceivable with fluid EC materials, offers huge potential for cooling applications.

13 pages, 6 figures. Submitted to Nature Energy