Pyroelectric Energy Conversion in Doped Hafnium Oxide (HfO2) Thin Films on Area-Enhanced Substrates

Low‐grade heat sources are abundant yet challenging to use for energy harvesting. Herein, the pyroelectric effect in Si‐doped HfO2 thin films is used to demonstrate thermal‐electric energy conversion. The 20 nm thin films are grown on an area‐enhanced substrate via atomic layer deposition, which enhances the power output by a factor of 19 in comparison to planar materials. Ferroelectric and pyroelectric properties of the Si‐doped HfO2 are investigated, and a large pyroelectric coefficient of -1442 mC m−2 K−1 is measured. Wireless power distribution using an infrared laser and pyroelectric Si‐doped HfO2 receiver is demonstrated, where Brayton‐style thermodynamic cycles are used to enhance the efficiency compared with simple resistive harvesting. Thereby, energy conversion cycles at 5 Hz produce net powers of 0.75 mW cm−2. The operating conditions of the power‐beaming circuit are optimized, and the performance is found to be ultimately limited by the series resistance of the electrodes. The thermal efficiency of the HfO2‐based pyroelectric is analyzed relative to classical pyroelectrics, and the loss mechanisms are discussed.