Rational Composition and Structural Control for Enhancing Thermoelectric Properties in p‐Type Bi_0.4Sb_1.6Te₃ Thin Films

Abstract Bi₂Te₃‐based thin films with high thermoelectric performance possess a full potential for application in thermoelectric devices. This work, reports p‐type Te‐excess Bi_0.4Sb_1.6Te₃ (BST) thin films with high power factor via composition and growth orientation optimization. Experimental characterizations show that the preferred growth orientation changes from (015) to (00l) with the increase of rapid annealing temperature, contributing to the high electrical conductivity of the Te‐excess BST thin films. The Te nanoparticles between the BST grain boundaries are observed via microstructure characterization; the composition regulation leads to the optimization of the carrier concentration and enhancement of Seebeck coefficient. As a result, the high power factor of 18.39 µW cm⁻¹ K⁻² is obtained at 500 K, over two times larger than that of BST thin film. This work establishes that rational composition and structural manipulations can significantly enhance the thermoelectric performance in p‐type Te–Bi_0.4Sb_1.6Te₃ thin films.