Thermoelectric technology enables all-solid-state direct and clean conversion between thermal energy and electrical energy, and is regarded as an effective strategy to address the issue of energy shortage. Especially in recent years, with the popularity of wearable devices, flexible thermoelectric devices, as an excellent self-powered technology, have experienced rapid development. Therefore, this review systematically summarizes recent advancements in this field. It begins with the fundamental thermoelectric principles and key performance evaluation parameters for flexible devices. Then we emphasize the design strategies to improve devices performance. It is followed by a critical discussion on several material systems. Later, we demonstrate different strategies for fabricating flexible devices based on thin films, fibers and fabrics. Furthermore, practical applications in energy harvesting, cooling, and sensing are also summarized. Finally, the review concludes the challenges and perspectives on future innovations in flexible thermoelectric devices.

Self-powered display systems that integrate alternating current electroluminescence (ACEL) devices with triboelectric nanogenerators (TENGs) have shown great promise in human-machine interaction, smart displays, and security communications within the Internet of Things (IoT). However, their development has been significantly limited by undesirable flickering, which arises from the pulsed output characteristics of TENGs. Here, high-performance persistent phosphors ((Ca_0.25Sr_0.75)S:Eu) are incorporated into the ZnS:Cu-based ACEL devices to overcome this limitation, achieving an extended afterglow lifetime of 81 s and a sustained red emission lasting over 200 s. By integrating with TENGs, a self-powered persistent display system is realized that maintains bright red-emission for over 15 s. The varying afterglow intensities post power-off can distinguish directional movement (forward or backward), enabling motion trajectory recording and recognition, as demonstrated using floor-mounted TENGs to drive persistent display arrays. This strategy offers a new pathway for advanced self-powered display systems and broadens their application potential in the IoT landscape.

Stretchable hybrid systems have been attracting tremendous attention for their essential role in soft robotics, on-skin electronics, and implantable devices. Both rigid and soft functional modules are typically required in those devices. Consequently, ensuring stable electrical contact between rigid and soft modules is a vital part. Here, we propose a simple, universal, and scalable strategy for the stretchable hybrid system through a highly precise printable liquid metal particle-based conductor and adhesive fluorine rubber substrate. The properties of liquid metal particle-based conductors could be easily tuned to realize high-precision patterning, large-scale printing, and the ability to print on various substrates. Additionally, the fluorine rubber substrate could form strong interfacial adhesion with various components and materials through simply pressing and heating, hence enabling stable electrical contact. Furthermore, we prepared a stretchable hybrid light-emitting diode (LED) display system and employed it in on-skin visualization of pressure levels, which perfectly combined rigid and soft modules, thus demonstrating the promising potential applications in complex multifunctional stretchable hybrid systems for emerging technologies.