Enhancement of thermoelectric performance in n-type PbTe1−ySey by doping Cr and tuning Te:Se ratio

• We achieved the highest room temperature ZT of ~0.6 by optimizing Cr doping.
• The peak ZT temperature increased with increasing concentration of Se.
• The average ZT improved due to improvement of room temperature ZT.
• Thermoelectric conversion efficiency of up to 13% could be achieved.

Lead telluride and its alloys have been extensively studied for medium temperature thermoelectric applications due to decent figure-of-merit (ZT) at temperature close to 900 K. However, little emphasis has been given to improve the ZT near room temperature. In this investigation, we report a systematic study of Cr doping in PbTe1−ySey with y=0, 0.25, 0.5, 0.75, 0.85, and 1. We found the peak ZT temperature increased with increasing concentration of Se. The highest ZT of ~0.6 at room temperature in Te-rich Cr0.015Pb0.985Te0.75Se0.25 was obtained due to a lowered thermal conductivity and enhanced power factor resulted from high Seebeck coefficient of about −220 µV K−1 and high Hall mobility ~1120 cm2 V−1 s−1 at room temperature. A room temperature ZT of ~0.5 and peak ZT of ~1 at about 573–673 K is shown by Se-rich sample Cr0.01Pb0.99Te0.25Se0.75. This improvement of the room temperature ZT improved the average ZT over a wide temperature range and could potentially lead to a single leg efficiency of thermoelectric conversion for Te-rich Cr0.015Pb0.985Te0.75Se0.25 up to ~11% and Se-rich Cr0.01Pb0.99Te0.25Se0.75 up to ~13% with cold side and hot side temperature at 300 K and 873 K, respectively, if matched with appropriate p-type legs.

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