High-Performance Sb2Te3 Thick Films via Diffusion-Induced Structural Tuning for Flexible Thermoelectric Energy Harvesting

Sb₂Te₃ is a widely studied p-type thermoelectric material with great potential for flexible energy harvesting applications. To enable stable power supply for wearable electronics, enhancing the output power of thermoelectric thin-film devices is imperative, where high-performance thick films are advantageous for boosting power generation efficiency. In this work, we successfully fabricated 10 μm Sb₂Te₃ thick films with high performance by combining thermal evaporation and a thermal diffusion process. Initially, we explored the thermoelectric properties of Sb₂Te₃ films with varying thicknesses and found that as the thickness increased, the electrical conductivity decreased significantly, leading to a decline in the power factor. To address this, we optimized the thermal diffusion temperature for 10 μm-thick Sb₂Te₃ films. This optimization substantially enhanced both electrical conductivity and power factor, achieving a remarkable room-temperature power factor of 25.0 μW cm^-1 K^-2. Building on this high-performance thick film, we developed a flexible planar thermoelectric device, which demonstrated an output voltage of 57 mV and a peak output power of 8.85 μW under a 60 °C temperature gradient. The output power density reached as high as 4.42 mW cm^-2. The device with only a 16.7% change in resistance after 800 bending cycles at a bending strain of 60%. This work presents a scalable and effective strategy to enhance the thermoelectric performance of thick Sb₂Te₃ films, accelerating their practical deployment in wearable energy harvesting systems.