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

Improved thermoelectric properties of p-Sb2Te3 and n-Bi2Te3 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 mu m - Kapton (R) polyimide). Seebeck coefficients of 194 mu V K-1 and - 233 mu V K-1 and electrical conductivities of 3.2 x 10(4) (Omega m)(-1) and 5.0 x 10(4) (Omega m)(-1) , lead to optimized power factors of 1.2 x 10(-3) W K-2 m(-1) and 2.7 x 10(-3) W K-2 m(-1), measured at 298 K, for flexible Sb2Te3 and Bi2Te3 films, respectively. The power factor value increases until a maximum of 2.3 x 10(-3) W m(-1) K-2 for the p-type film, and to 5.9 x 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 Sb2Te3 and Bi2Te3 films, at room temperature, with thickness below 1 mu m. A flexible thermopile sensor based on p - n films is presented, into possible thermal sensing. The thermoelectric device shows a responsivity of 0.05 VW-1 and a specific detectivity of 1.6 x 10(7) cm root Hz W-1. (C) 2018 Elsevier B.V. All rights reserved.