n -Type to p -Type Transition of Electrical Conduction in Silver (Ag)-Modified Bi 2 Te 3 Nanosheets

Bi 2 Te 3 exhibits n -type conduction behaviour due to Te vacancies. We demonstrate that upon modification of Bi 2 Te 3 flower-like nanosheets with Ag, a transition of electrical conduction from n -type to p -type occurs. The highest Seebeck coefficients of pure Bi 2 Te 3 nanosheets and Ag-Bi 2 Te 3 composites were found to be approximately − 175 μV/K and + 179 µV/K, respectively, at 675 K. The electrical resistivity of the composite material increases with increasing Ag content. The transition of conduction in composite material is attributed to the formation of a p–n junction (energy barrier ~0.6 eV) for electrons at the Ag/Bi 2 Te 3 interface, resulting in facile movement of minority carriers (holes).