  Dielectric screening plays an important role in reducing the strength of
carrier scattering and trapping by point defects for many semiconductors such
as the halide perovskite solar materials. However, it was rarely considered as
a screen to find new electronic semiconductors. We performed a material search
study using the dielectric properties as a screen to identify potential
electronic materials in the class of metal-pnictide ternary sulfosalts,
containing Bi or Sb. These salts are basically ionic due to the
electronegativity difference between the S and both the metal and pnictogen
elements. However, we do find significant cross-gap hybridization between the S
p-derived valence bands and pnictogen p-derived conduction bands in many of the
materials. This leads to enhanced Born effective charges, and in several cases,
highly enhanced dielectric constants. We find a chemical rule for high
dielectric constants in terms of the bond connectivity of the
pnictogen-chalcogen part of the crystal structure. We additionally find a
series of compounds with low effective mass, high dielectric constant and other
properties that suggest good performance as electronic materials and also
several potential thermoelectric compounds. Experimental optical data and solar
conversion efficiency are reported for Sn-Sb-S samples, and results in accord
with predicted good performance are found. The results illustrate the utility
of dielectric properties as a screen for identifying complex semiconductors.
