Synthesis of Multishell Nanoplates by Consecutive Epitaxial Growth of Bi₂Se₃ and Bi₂Te₃ Nanoplates and Enhanced Thermoelectric Properties

We herein demonstrate the successive epitaxial growth of Bi₂Te₃ and Bi₂Se₃ on seed nanoplates for the scalable synthesis of heterostructured nanoplates (Bi₂Se₃@Bi₂Te₃) and multishell nanoplates (Bi₂Se₃@Bi₂Te₃@Bi₂Se₃, Bi₂Se₃@Bi₂Te₃@Bi₂Se₃@Bi₂Te₃). The relative dimensions of the constituting layers are controllable via the molar ratios of the precursors added to the seed nanoplate solution. Reduction of the precursors produces nanoparticles that attach preferentially to the sides of the seed nanoplates. Once attached, the nanoparticles reorganize epitaxially on the seed crystal lattices to form single-crystalline core-shell nanoplates. The nanoplates, initially 100 nm wide, grew laterally to 620 nm in the multishell structure, while their thickness increased more moderately, from 5 to 20 nm. The nanoplates were pelletized into bulk samples by spark plasma sintering and their thermoelectric properties are compared. A peak thermoelectric figure of merit (ZT) ∼0.71 was obtained at 450 K for the bulk of Bi₂Se₃@Bi₂Te₃ nanoplates by simultaneous modulation of electronic and thermal transport in the presence of highly dense grain and phase boundaries.