A theoretical analysis of single-barrier thermionic emission cooling in semiconducting materials is performed using Fermi-Dirac statistics. Both maximum cooling and coefficient of performance are evaluated. It is shown that the performance of a thermionic refrigerator is governed by the same materials factor as thermoelectric devices. For all known materials, single-barrier thermionic refrigeration is less effective and less efficient than thermoelectric refrigeration. (C) 2001 American Institute of Physics.