New pyroelectric figures of merit for harvesting dynamic temperature fluctuations†

Pyroelectric materials are attracting increasing attention for a variety of applications including thermal imaging, thermal sensing, and energy harvesting. To select and design pyroelectric materials with optimal performance, figures of merit (FoMs) are utilized in terms of energy, voltage, and current sensitivity. However, existing FoMs do not take into account heat transfer parameters, such as thermal conductivity and thermal diffusivity. To address this challenge, this paper formulates new performance figures of merit for the selection and design of pyroelectric materials for harvesting dynamic temperature fluctuations. The new figures of merit are of interest for the selection of pyroelectric materials, the design of new materials, or the creation of novel composites for pyroelectric applications, in particular when there is a need for rapid thermal cycles to increase the frequency of operation and maximize the power output for thermal harvesting. High performance materials based on the new figures of merit are highlighted and evaluated, and comparisons between the material classes are discussed, including polycrystalline ceramics, single crystal materials, polymers, thin films, composites and 2D materials. Potential future high-performance pyroelectric materials for thermal harvesting are outlined.