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

TL;DR

This paper reports the first direct measurements of electrocaloric effects in ferroelectric nematic liquid crystals, showing significant temperature changes and high electrocaloric strength, with potential for efficient cooling applications.

Contribution

It introduces ferroelectric nematic liquid crystals as a new electrocaloric material with tunable temperature range and demonstrates their superior electrocaloric strength compared to existing materials.

Findings

Direct measurements show temperature jumps of ~0.2 K at low fields.

Up to 1.6 K temperature change at higher fields.

Electrocaloric strength up to 100% higher than incumbent materials.

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.