Properties of bismuth based Bi2A3 (A = S, Se, Te) chalcogenides for optoelectronic and thermoelectric applications

Structural, electronic, optical, mechanical, thermoelectric and dielectric properties of binary Bi(2)A(3) (A = S, Se, Te) chalcogenide semiconductors are studied by first-principles approach. Bismuth sulfide (Bi2S3) is found to be structurally stable in orthorhombic structure while bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are stable in trigonal structure. Calculated mechanical properties reveal that all three Bi(2)A(3) (A = S, Se, Te) compounds fulfil the mechanical stability criteria. Band structure calculations reveal that the Bi2S3 exhibits direct optical band gap (E-g = 1. 58 eV) which lies in the near-infrared (NIR) region, while the calculated E-g of Bi2Se3 and Bi2Te3 are found to be 0.53 eV and 0.35 eV, respectively lying in the far-infrared region. For Bi2S3 and Bi2Se3 compounds, the calculated dielectric properties show strong anisotropic behavior, while negligible anisotropic dielectric behavior is observed for Bi2Te3. Calculated optical properties show that all three Bi(2)A(3) compounds possess high absorption coefficient (> 10(4) cm(-1)). For all three Bi(2)A(3) (A = S, Se, Te) compounds, the calculated optical conductivity show prominent peak corresponding to the occurrence of optical conduction at energies 3.36 eV, 2.65 eV and 2.02 eV respectively. Calculated optical results support the results deduced from band structures and density of states spectra. Optical properties and dielectric behavior suggest that the Bi2S3 compound has suitable band gap and has potential to use for photovoltaic applications while Bi(2)A(3) (A = Se, Te) compounds could be used in infrared detectors and other optical devices. Calculated thermal properties reveal that the Bi(2)A(3) (A = S, Se, Te) chalcogenides could be potential materials for thermoelectric applications.