Enhanced Electrical Transport Properties via Defect Control for Screen-Printed Bi₂Te₃ Films over a Wide Temperature...

The application of screen-printed thin-film thermoelectric (TE) devices is still in its infancy, mainly due to low TE performance of screen-printed films and especially the poor electrical transport properties. Herein, we design and prepare a high-performance screen-printed Bi₂Te₃ film through introducing excessive Te-based nanosolder (Te-NS) to simultaneously realize the conduction channel construction and defect control. On one hand, the promoted carrier migration makes the electrical conductivity dramatically rise about 7 times, with a maximum power factor of 4.65 μW cm ^-1 K ^-2. Meanwhile, the defect formation mechanism in the screen-printed Bi₂Te₃ film after the introduction of Te-NS is also in-depth studied, and the bipolar conduction is reduced by increased generation of Te^• and/or more suppression of Bi^', resulting in a postponed temperature of the maximum Seebeck coefficient. Hence, the large engineering power factor is achieved with excellent temperature linearity, indicating a possibility of screen-printed film application in a large temperature region. A TE device with a single leg has been fabricated to further demonstrate the generation validity. An open-circuit voltage of 11.34 mV and a maximum output power of 27.1 μW at a temperature gradient of 105 K have been achieved over a wide temperature range from 303 to 478 K. This study provides a theoretical and practical basis for the performance improvement of screen-printed TE films and devices.