Optimized thermoelectric properties and geometry parameters of annular thin-film thermoelectric generators using n-type Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ thin films for energy harvesting

Thermoelectric generators can be used as energy harvesting for power supply in Internet of Thing sensors. Here, material properties and geometry parameters were investigated to improve the annular thin-film thermoelectric generator (ATTEG) output performances. The as-deposited and annealed n-type Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ were deposited by radio frequency magnetron sputtering which resulted in higher Seebeck coefficient and electrical conductivity of annealed thin films. The temperature distributions and output performances in ATTEG were calculated using numerical simulation to identify the geometry parameters. The results showed that thinner substrate with higher output performances, larger legs number with higher output voltage, and a peak point in the maximum output power was observed for the effect of the angle ratio of p-type leg to n-type leg with optimal value of 1. We fabricated ATTEGs with different TE legs to identify the machining accuracy, and the ATTEG with 12 legs resulted in output voltage of 27.7 mV, the maximum output power of 169.0 nW and power density of 127.39 nW∕cm² at a temperature difference of 23 K. Hollowing and nicking on substrate were proposed as further improvement, and resulted in increasement of 6.6% in output voltage and 13.6% in the maximum output power.