Pyramid-structured VO2-based thin films with large emissivity tunability for thermochromic radiators

Abstract

Structure-engineering has proven successful in enhancing the thermochromic properties of VO2-based film for smart thermal management under dynamic thermal loads. However, traditional multilayer structures based on interlayer interference and grating structures based on resonance effect exhibit certain wavelength selectivity, thereby hindering broadband absorption. This limitation constrains the improvement of high temperature integrated emissivity (εH), posing great challenges for achieving greater average emissivity tunability (Δε=εH-εL). In this work, we propose a VO2-based 3D pyramid structured film by combining the multilayer structure with the grating structure, achieving an unprecedented high emissivity tunability Δε reaching 0.68. Based on the Magneto-polaron (MP) resonance effect, high absorption over a wide spectral range at high temperature is achieved, with εH of 0.954. Through optimizing the VO2 thickness δ to 30 nm and tilt angle β to 80° respectively, we achieve optimal thermochromic performance of the film. Compared with conventional multilayer and grating regimes, the pyramid textured structure proposed in this work demonstrates a larger design space, which can be a reference for the design and optimization of spacecraft thermal control skin.