Enhanced thermoelectric properties of Sb2Te3 and Bi2Te3 films for flexible thermal sensors

Abstract Improved thermoelectric properties of p-Sb 2 Te 3 and n-Bi 2 Te 3 films deposited by thermal co-evaporation at 503 K and 543 K, respectively, are reported, by using two types of substrate (borosilicate glass and 25 μm - Kapton ® polyimide). Seebeck coefficients of 194 μV K −1 and - 233 μV K −1 and electrical conductivities of 3.2 × 10 4 (Ω m) −1 and 5.0 × 10 4 (Ω m) −1 , lead to optimized power factors of 1.2 × 10 −3  W K −2  m −1 and 2.7 × 10 −3  W K −2  m −1 , measured at 298 K, for flexible Sb 2 Te 3 and Bi 2 Te 3 films, respectively. The power factor value increases until a maximum of 2.3 × 10 −3  W m −1  K −2 for the p-type film, and to 5.9 × 10 −3  W m −1  K −2 for the n-type film, at 373 K, respectively. An improvement of more than two times on the power factor value is observed when compared with the actual state-of-art for flexible Sb 2 Te 3 and Bi 2 Te 3 films, at room temperature, with thickness below 1 μm. A flexible thermopile sensor based on p - n films is presented, into possible thermal sensing. The thermoelectric device shows a responsivity of 0.05 V W −1 and a specific detectivity of 1.6 × 10 7  cm √Hz W −1 .