  We present a general principle for the rational design of dielectric optical
antennas with optimal solar absorption enhancement: leaky mode engineering.
This builds upon our previous study that demonstrates the solar absorption of a
material with a given volume only dependent on the density and the radiative
loss of leaky modes of the material. Here we systematically examine the
correlation among the modal properties (density and radiative loss) of leaky
modes, physical features, and solar absorption of dielectric antenna
structures. Our analysis clearly points out the general guidelineS for the
design of dielectric optical antennas with optimal solar absorption
enhancement: a) using 0D structures; b) the shape does not matter much; c)
heterostructuring with non-absorbing materials is a promising strategy; d) the
design of a large-scale nanostructure array can use the solar absorption of
single nanostructures as a reasonable reference.
