The application of non-equilibrium transport techniques to narrow-gap semiconductor materials has produced practical, negative luminescent devices. These structures contravene Kirchhoff's law because they will absorb infrared radiation in a limited band without emitting it. They have many potentially important applications which include toxic gas sensing, cold shields for IR detectors, radiometric reference sources and dynamic infrared scene projectors. (C) 1997 Published by Elsevier Science B.V.