Theoretical study of structural, electronic, optical, thermoelectric and photovoltaic properties of chalcopyrite semiconductors AgGaTe₂ and AgGaSe₂ compounds for photocatalytic CO₂ reduction

We present a first principles investigation of structural, electronic, optical, thermoelectric, and photovoltaic properties of the chalcopyrite AgGaTe₂ and AgGaSe₂ compounds, using the full potential linearized augmented plane wave method, as part of the density functional theory. The calculated lattice parameters are in good agreement with the experimental and theoretical values. The band gaps energies of the studied systems were determined using different exchange-correlation functionals such as GGA-PBEsol, EV-GGA, YS-PBE0, and TB-mBJ methods. It is found that both compounds are semiconductors with a direct band gap (Γ-Γ). This direct band gap means that AgGaTe₂ and AgGaSe₂ materials can be used in the optical and optoelectronic devices. In accordance with this, the photovoltaic efficiency of the semiconducting was investigated using Solar Cell Capacitance Simulator-1D software. The best efficiencies of 23.76% and 17.52% were obtained at a thickness of 2.2 μm for AgGaTe₂ and AgGaSe₂ compounds, respectively. The lattice thermal conductivities for both compounds are remarkably low, with values at 300 K of 0.033 and 0.013 W×m^− 1×K^− 1 for AgGaTe₂ and AgGaSe₂, respectively. In addition, we studied the thermoelectric properties at room temperature, using semi-classical Boltzmann transport theory. The positive values of the Seebeck coefficient for both compounds exceed their absolute negative values, indicating that AgGaTe₂ and AgGaSe₂ are p-type materials. The obtained values of figure of merit for AgGaTe₂ and AgGaSe₂ are 0.70 and 0.81, respectively. The calculated results reveal that both chalcopyrites are potential thermoelectric materials. The band-gap edge potentials for AgGaTe₂ and AgGaSe₂ are − 0.65 eV and − 0.635 eV, respectively, which are below the required potential of -0.61 eV for CO₂ reduction to formic acid. This result means that AgGaTe₂ and AgGaSe₂ are suitable compounds for photocatalytic CO₂ reduction.