GST-VO 2 -based near-field multistage radiative thermal rectifier

A near-field multistage radiative thermal rectifier is proposed based on two different phase-change materials, which can achieve multistage thermal rectification with different rectification ratios. The phase-change materials vanadium dioxide (VO 2 ) and Ge 2 Sb 2 Te 5 (GST), with different metal-insulator transition temperatures, are utilized within the active terminal of thermal rectifier. Four types of active terminal structures, including multi-film and composite nanograting structures, are introduced to explore to multistage thermal rectification. Our calculations find that the active terminal composed of a one-dimensional VO 2 grating atop a GST thin film is the most suitable for multistage thermal rectification due to its realization of well-distributed and flexible thermal rectification. Furthermore, it is found that the passive terminal temperature of thermal rectifier can significantly affect the multistage radiative thermal rectification by modifying the rectification ratio and adjusting the stage number of multistage thermal rectification. This work sheds light on the role of different phase-change materials within the design of promising radiative thermal rectifiers boasting multistage thermal rectification.