Advances and challenges in inorganic bulk-based flexible thermoelectric devices

The development of flexible thermoelectric devices (F-TEDs) has significantly improved their thermoelectric performance and unique flexibility, with increasing efforts directed toward standardization and commercialization. Among the various types of F-TEDs, those incorporating all-inorganic bulk materials are more practical and broadly applicable due to the superior thermoelectric performance of these materials compared to F-TEDs using flexible films and fibers. In recent years, innovative design approaches for inorganic bulk-based F-TEDs have emerged, showcasing their distinct advantages. This review provides a timely and comprehensive summary of the research progress on inorganic bulk-based F-TEDs utilizing thermoelectric materials. We begin by discussing advancements in newly developed inorganic bulks, including traditional near-room-temperature bismuth-telluride-based materials, and more recent plastic materials. We then explore design strategies and innovations in inorganic bulk-based F-TEDs, covering areas such as computational modeling, device structures, heat flow analysis, advanced fabrication techniques, diffusion barriers, flexibilization strategies, liquid metal interconnects, and flexible heat sinks. Additionally, we review the testing standards for F-TEDs and highlight the recent application advancements in flexible power generation, cooling, and heating. Finally, we address the current challenges in this field and offer insights into future development prospects. This work is essential for advancing the design, application, standardization, and commercialization of F-TEDs.