  For the transition into a sustainable mode of energy usage, it is important
to develop photovoltaic materials that exhibit better solar-to-electricity
conversion efficiencies, a direct optimal band gap, and made of non-toxic,
earth abundant elements compared to the state-of-the-art silicon photovoltaics.
Here, we explore the non-redox-active pnictide chemical space, including binary
A$_3$B$_2$, ternary AA'$_2$B$_2$, and quaternary AA'A"B$_2$ compounds (A, A',
A" = Ca, Sr, or Zn; B = N or P), as candidate beyond-Si photovoltaics using
density functional theory calculations. Specifically, we evaluate the ground
state configurations, band gaps, and 0 K thermodynamic stability for all 20
pnictide compositions considered, besides computing the formation energy of
cation vacancies, anion vacancies, and cation anti-sites in a subset of
candidate compounds. Importantly, we identify SrZn$_2$N$_2$, SrZn$_2$P$_2$, and
CaZn$_2$P$_2$ to be promising candidates, exhibiting optimal (1.1-1.5 eV)
hybrid-functional-calculated band gaps, stability at 0 K, and high resistance
to point defects (formation energies $>$1 eV), while other possible candidates
include ZnCa$_2$N$_2$ and ZnSr$_2$N$_2$, which may be susceptible to N-vacancy
formation. We hope that our study will contribute to the practical development
of pnictide semiconductors as beyond-silicon light absorbers.
