Tuning band structure and texture for improved thermoelectric performance in BiSe

Abstract

Layer-structured BiSe has emerged as a promising Te-free thermoelectric (TE) material because of its intrinsic low thermal conductivity. Herein we report the optimization of TE performance for BiSe through In doping to tune the band structure and the proper annealing treatment to adjust the texture. The first-principles calculations and doping experiments reveal that In dopant in BiSe introduces additional energy levels near Fermi level leading to the increase of carrier effective mass. The preferred orientation of (00l) plane in BiSe was well adjusted to optimize the electrical conductivity and Seebeck coefficient. Through tuning band structure and texture simultaneously, the Bi0.995In0.005Se sample exhibited a maximum figure of merit ZT value of 0.33 at 523 K, which is about 43.5 % higher than that of the pristine BiSe sample without the texture adjustment. This work presents a potential route to promote the TE performance of layer-structured materials.