Bismuth Telluride-Based Thermoelectric Thin Films: From Deposition Strategies to Flexible and Wearable Devices

Thermoelectric (TE) materials convert thermal gradients into electrical energy, offering asolid-state route to sustainable power generation and precision cooling. Among these, Bi₂Te₃-based thin films including alloys such as Bi₂Te_3-xSe_x and Bi_xSb_2-xTe₃ are key candidates for microenergy systems due to their reduced dimensionality, which enhances phonon scattering and enables precise charge transport control. Thin-film architectures provide seamless integration with flexible substrates, engineered interfaces that suppress lattice thermal conductivity (κ_L), and millisecond-scale thermal response. This review critically examines fabrication techniques for Bi₂Te₃-based thin films, including physical vapor deposition (coevaporation, pulsed laser deposition, and magnetron sputtering), low-pressure chemical vapor deposition, solution-based methods (electrochemical deposition, spin-coating, and wet-chemical synthesis) and screen printing technique. Each deposition method is evaluated for stoichiometric control, microstructure, and interfacial quality, with process parameters linked to TE performance and optimized films demonstrated in flexible, wearable, and conformal devices. The analysis reveals a fundamental trade-off between TE efficiency, manufacturing scalability, and mechanical durability-a trilemma that no single deposition method can resolve. This work bridges advanced fabrication science with practical device integration for emerging flexible electronics, addressing key challenges including scalability, contact resistance, and sustainable manufacturing.