Ultrahigh-rectification near-field radiative thermal diode using infrared-transparent film backsided phase-transition metasurface

We present a theoretical study of near-field radiative thermal rectification combining phase-transition and high-infrared-transmittance materials. The phase-transition material vanadium dioxide (VO2), with a metal-insulator transition near 341 K, is utilized under a reasonable temperature. Four types of high-infrared-transmittance materials, including potassium bromide, sodium chloride, polyethylene, and magnesium fluoride, are introduced as thin film substrates under a VO2 grating on one side of the near-field rectifier. We explore the effects of various high-infrared-transmittance thin-film substrates and relevant geometric parameters on the thermal rectification of the device. The results show that thermal rectification can be greatly enhanced by using a one-dimensional VO2 grating backed with a high-infrared-transmittance thin-film substrate. With the introduction of a high-infrared-transmittance substrate, the rectification ratio is dramatically boosted due to the enhancement of the substrate transmittance. This work predicts a remarkable rectification ratio as high as 161—greater than the recently reported peak values for comparable near-field radiative thermal rectification. The results outlined herein will shed light on the rapidly expanding fields of nanoscale thermal harvesting, conversion, and management.