Bi$_2$Te$_3$-based flexible thermoelectrics

Bi$_2$Te$_3$-based materials stand out as the top-performing material for thermoelectric applications at room temperature. However, its inherent rigidity has posed challenges for widespread usage in flexible thermoelectric conversion systems. Recent endeavors have focused on achieving Bi$_2$Te$_3$-based flexible films through bulk thinning, physical/chemical deposition, paste casting, as well as the template method. These efforts have led to a surge in research publications. This review aims to offer a comprehensive update on the synthesis approaches, microstructures, thermoelectric performances/flexibility, and the underlying mechanisms. Future research should focus on investigating innovative deposition techniques, exploring new composite phases/templates, refining fabrication parameters, and among others, to enhance the thermoelectric performances as well as flexibility.