  Computational searching and screening of new functional materials exploiting
earth abundant elements can accelerate developments of their energy
applications. Based on a state-of-the-art materials search algorithm and ab
initio calculations, we demonstrate a recently suggested stable silicon oxide
with a layered structure (Si$_{3}$O) as an ideal photovoltaic material. With
many-body first-principles approaches, the monolayer and layered bulk of
Si$_{3}$O show direct quasiparticle gaps of 1.85 eV and 1.25 eV, respectively,
while an optical gap of about 1.2 eV is nearly independent of the number of
layers. Spectroscopic limited maximum efficiency (SLME) is estimated to be 27%
for a thickness of 0.5 {\mu}m, making it a promising candidate for solar energy
applications.
