  The bulk photovoltaic effect is a long-known but poorly understood
phenomenon. Recently, however, the multiferroic bismuth ferrite has been
observed to produce strong photovoltaic response to visible light, suggesting
that the effect has been underexploited as well. Here we present three polar
oxides in the LiNbO$_3$ structure that we predict to have band gaps in the 1-2
eV range and very high bulk photovoltaic response: PbNiO$_3$,
Mg$_{1/2}$Zn$_{1/2}$PbO$_3$, and LiBiO$_3$. All three have band gaps determined
by cations with $d^{10}s^0$ electronic configurations, leading to conduction
bands composed of cation $s$-orbitals and O $p$-orbitals. This both
dramatically lowers the band gap and increases the bulk photovoltaic response
by as much as an order of magnitude over previous materials, demonstrating the
potential for high-performing bulk photovoltaics.
