The electronic structure, optical, and thermoelectric properties of novel Bi ₂ PbCh ₄ (Ch = Se, Te) materials: insights from first-principles study

Ternary chalcogenides have attracted much interest because of their potential for use in sustainable energy applications due to their tunable electronic, optical, and transport characteristics. This work examined the structural, electronic, optoelectronic, and thermoelectric properties of novel Bi₂PbSe₄ and Bi₂PbTe₄ chalcogenides through density functional theory. The predicted energy gap values measured with the TB-mBJ and PBE-GGA are 1.12 and 0.71 eV for Bi₂PbSe₄ and 1.08 and 0.82 eV for Bi₂PbTe_4, respectively. Both materials behave as semiconductors and have direct energy gaps, which makes them attractive for solar energy applications. COHP study illustrates that strong Bi-chalcogen bonding characterizes the valence band, whereas antibonding states prevail above the Fermi level in both Bi₂PbSe₄ and Bi₂PbTe₄. Their promise as absorber materials in photovoltaic devices is highlighted by optical investigations that show considerable absorption in the visible and infrared ranges, high dielectric constants, and higher photoconversion performance. The Seebeck coefficient, lattice thermal conductivity, and electrical conductivity were employed to assess thermoelectric features. These ternary materials are suitable for integrated solar energy collecting and conversion systems because of their outstanding optical absorption and thermoelectric potential. The structure-property interactions of these materials are explained by this study, opening the door for testing and more optimization for improved energy devices.