Realizing high thermoelectric performance in highly (0l0)-textured flexible Cu2Se thin film for wearable energy harvesting

Searching for eco-friendly and earth-abundant materials to supersede traditional high-cost bismuth telluride for fabricating wearable devices is of great significance in thermoelectrics. In this work, promising flexible Cu2Se based thin films with high thermoelectric performance is successfully fabricated via a facile co-sputtering method. Experimental results indicate that excess Cu in Cu2Se films leads to the decrease of carrier concentration by suppressing the formation of Cu vacancies and donating electrons, benefiting to achieve high Seebeck coefficient. Moreover, Cu-excess Cu2Se films have highly (0l0) preferred orientation and extra high carrier mobility, maintaining the decent electrical conductivity in the whole measurement temperature range. Combined with the low thermal conductivity, a maximum ZT of 0.42 is obtained at 275 degrees C from the Cu-excess Cu2Se due to the simultaneous optimization both of electrical and heat transport. Subsequently, a flexible thermoelectric device assembled with high performance Cu2Se films exhibits a maximum power density of 4.28 Wm(-2) at a temperature difference of 50 degrees C, which thermal stability is greatly improved after introducing a molybdenum buffer layer into electrode layer. Therefore, this work demonstrates that rational microstructure manipulations and connection technology improvement can achieve high performance in the flexible thermoelectric device, which possess potential in wearable applications. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Searching for eco-friendly and earth-abundant materials to replace traditional high-cost bismuth telluride for wearable device fabrication is important in thermoelectrics. In this study, flexible Cu2Se thin films with high thermoelectric performance were successfully fabricated using a simple co-sputtering method. Excess Cu in Cu2Se films was found to decrease carrier concentration, resulting in a higher Seebeck coefficient. Additionally, Cu-excess Cu2Se films exhibited preferred orientation and high carrier mobility, leading to decent electrical conductivity and low thermal conductivity. A maximum ZT value of 0.42 was achieved at 275 degrees C, indicating the simultaneous optimization of electrical and heat transport. Furthermore, a flexible thermoelectric device assembled with high-performance Cu2Se films showed a maximum power density of 4.28 Wm(-2) at a temperature difference of 50 degrees C, and its thermal stability was greatly improved by introducing a molybdenum buffer layer. This study demonstrates the potential of rational microstructure manipulation and connection technology improvement in achieving high performance in flexible thermoelectric devices with wearable applications.