Growth of high carrier mobility 2-Dimensional hexagonal Bi2Te3-xSex nanoplatelets and its thermoelectric performance studies

Abstract

Morphologically controlled growth of selenium-doped 2-Dimensional (2D) Bi2Te3-xSex nanoplatelets have been optimized by solvothermal synthesis using polyvinyl-pyrro-lidone (PVP) surfactant from the pre-optimized growth conditions of 2D-Bi2Te3 hexagonal nanoplatelet. An optimization was carried out using the Se-doping of x = 0.3 under variable growth durations of 4 h, 8 h, and 12 h. X-ray powder diffraction studies confirmed the complete crystallization with a pure phase of 2D-Bi2Te3-xSex at an extended duration of 12 h synthesis. Crystallization with defined hexagonal morphology was confirmed by FESEM analysis. Selenium doping into the 2D-Bi2Te3-xSex lattice from x = 0.1 to x = 0.4 indicates a step-by-step shift in the 2θ value of the (015) predominant peak towards higher 2θ values. Raman analysis revealed the alteration of the appearance of A1u2 to A1g2 upon the lattice inclusion of “Se” in the place of “Te”. Hall measurements on the consolidated pellet of 2D-Bi2Te3-xSex resulted in the highest electron mobility of 1675 cm2V−1s−1 with carrier concentration of 2.9 × 1018 cm−3 for Se-doping x = 0.2. Thermal conductivity analysis in comparison with the total thermal conductivity and the calculated electronic thermal conductivity revealed the lowest lattice thermal conductivity of 0.17 Wm−1K−1 for the Se-doping x = 0.2 after the correction for structural anisotropy factor (f). The highest thermoelectric figure of merit of 0.74 was achieved in this course of work.