Room-Temperature Electrocaloric Effect in Layered Ferroelectric CuInP₂S₆ for Solid-State Refrigeration

Abstract

A material with reversible temperature change capability under an external electric field, known as the electrocaloric effect (ECE), has long been considered as a promising solid-state cooling solution. However, electrocaloric (EC) performance of EC materials generally is not sufficiently high for real cooling applications. As a result, exploring EC materials with high performance is of great interest and importance. Here, we report on the ECE of ferroelectric materials with van der Waals layered structure (CuInP2S6 or CIPS in this work in particular).Over 60% polarization charge change is observed within a temperature change of only 10 K at Curie temperature. Large adiabatic temperature change (|ΔT|) of 3.3 K, isothermal entropy change (|ΔS|) of 5.8 J kg -1 K -1 at |ΔE|=142.0 kV cm -1 at 315 K (above and near room temperature) are achieved, with a large EC strength (|ΔT|/|ΔE|) of 29.5 mK cm kV -1 . The ECE of CIPS is also investigated theoretically by numerical simulation and a further EC performance projection is provided.Electrocaloric refrigerators using electrocaloric materials are low noise, environmentfriendly and can be scaled down to small dimensions, compared to the common vaporcompression refrigerators. 1-13 Electrocaloric cooling is also much easier and lower cost to realize compared to other field induced cooling techniques such as magnetocaloric and mechanocaloric cooling, because the electric field is easily to be realized and accessible. Thus, electrocaloric effect is promising for future cooling applications, especially in micro-or nano-scale such as onchip cooling. Electrocaloric effect in ferroelectric materials is of special interest because of the large polarization change near the ferroelectric-paraelectric (FE-PE) phase transition temperature 21 TOC.

Review on Recent Developments in 2D Ferroelectrics: Theories and Applications

“…For example, the pyroelectric effect and the electrocaloric effect in the 2D ferroelectrics are promising enough to play a crucial role in nano-sized thermoelectronics. [119] Figure 19. a) Scheme of spin device based on SnTe.…”

Recent Advances in 2D Layered Phosphorous Compounds

“…confirmed the ferroelectric‐paraelectric phase transition in CuInP 2 S 6 flakes at 315 K through temperature‐dependent Raman measurement. [ 104 ] The Raman peaks showed dramatic loss in intensity as well as broadening when the temperature is below 315 K (Figure 5e). [ 104 ] Other than CuInP 2 S 6 , few‐layer CuCrP 2 S 6 has also been demonstrated to be ferroelectric at room‐temperature.…”

“…[ 104 ] The Raman peaks showed dramatic loss in intensity as well as broadening when the temperature is below 315 K (Figure 5e). [ 104 ] Other than CuInP 2 S 6 , few‐layer CuCrP 2 S 6 has also been demonstrated to be ferroelectric at room‐temperature. [ 105 ] Achieving ferroelectricity in 2D limit greatly expands the functionalities of 2D materials and opens up possibilities for novel applications as well as van der Waals heterostructures based on 2D ferroelectric materials.…”

Understanding Microscopic Operating Mechanisms of a van der Waals Planar Ferroelectric Memristor

“…Robust ferroelectricity in the few‐ and mono‐layer limit has been demonstrated in these materials, including the group‐IV monochalcogenides, [ 10–12 ] CuInP 2 S 6 , WTe 2 , and MoSe 2 , [ 13–16 ] which is desirable for realizing ultrathin devices. [ 17–20 ] Furthermore, the van der Waals bonding allows for straightforward integration of ferroelectrics and other materials, for example ferromagnets, providing opportunities to explore novel device concepts such as multiferroics. [ 21–24 ] Among newly discovered van der Waals ferroelectrics, α‐phase semiconducting In 2 Se 3 (α‐In 2 Se 3 ) has unique interlinked out‐of‐plane (OOP) and in‐plane (IP) polarizations that are sustained by covalent bonding, [ 25–31 ] suggesting that the OOP polarization can be switched via both external OOP and IP electric fields.…”