Clearly TPV devices are of considerable interest for power generation. For practical devices it is desirable to have high efficiencies combined with low temperature operation. Photovoltaic cells which can convert the energy at the longer wavelengths of interest are needed to complete such a system. The spectral emission peak of Yb2O3is well matched to the band gap of Si; however, the longer wavelength, spectral emissions of other rare earth oxides can also be exploited through the use of III–V semiconductor compounds such as GaSb or alloys of GaInAsSb. By doping GaSb with InAs, the band gap of the resulting material can be effectively varied depending upon the concentration of InAs in the quaternary alloy. The ability to tailor the emitter materials and, in conjunction, the photovoltaic materials leads to greater efficiencies through spectral matching. Two binary rare earth oxide combinations, Er2O3/Ho2O3and Er2O3/Yb2O3, were studied. The mixtures were found to give multiple peak spectral emission in the wavelengths of interest. The intensity of the peaks were compositionally dependent though it did not vary in a linear fashion. Photon efficiencies of the molecular beam epitaxially (MBE) grown GaSb cell and GaInAsSb quaternary cell were measured when used in conjunction with the Er2O3/Ho2O3emitters in which the concentration of Er2O3and Ho2O3were varied. The results demonstrated promise for further work. ©1996 American Institute of Physics.