First-principles calculations of structural, electronic, optical and thermoelectric properties of doped binary chalcogenides Sn1-xAxSe (A= Au and Ag) for energy applications

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn1-xAxSe (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn1-xAxSe (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From epsilon 2(omega) spectra, it is evident that Sn1-xAxSe (A = Au and Ag) absorbs maximum number of incident photons in infrared (at-0.5 eV) and visible (at-2.2 eV) regions. The calculated values of n(omega) are 2.27 and 2.58 for Sn1-xAgxSe and Sn1-xAuxSe, respectively. We can confirm that Sn1-xAxSe (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties.