  In the quest for efficient and cost-effective photovoltaic absorber materials
beyond silicon, considerable attention has been directed toward exploring
alternatives. One such material, zincblende-derived Cu2ZnSnS4 (CZTS), has shown
promise due to its ideal band-gap size and high absorption coefficient.
However, challenges such as structural defects and secondary phase formation
have hindered its development. In this study, we examine the potential of
another compound Cu2ZnSnO4 (CZTO) with a similar composition to CZTS as a
promising alternative. Employing ab initio density function theory (DFT)
calculations in combination with an evolutionary structure prediction
algorithm, we identify that the crystalline phase of the delafossite structure
is the most stable among the 900 (meta)stable CZTO. Its thermodynamic stability
at room temperature is also confirmed by the molecular dynamics study.
Excitingly, this new phase of CZTO displays a direct band gap where the
dipole-allowed transition occurs, making it a strong candidate for efficient
light absorption. Furthermore, the estimation of spectroscopic limited maximum
efficiency (SLME) directly demonstrates the high potential of delafossite-CZTO
as a photovoltaic absorber. Our numerical results suggest that delafossite-CZTO
holds another promise for future photovoltaic applications.
