Thermophotovoltaic (TPV) cells convert thermal energy to electricity. Modularity, portability, silent operation, absence of moving parts, reduced air pollution, rapid start‐up, high power densities, potentially high conversion efficiencies, choice of a wide range of heat sources employing fossil fuels, biomass, and even solar radiation are key advantages of TPV cells in comparison with fuel cells, thermionic and thermoelectric convertors, and heat engines. The potential applications of TPV systems include: remote electricity supplies, transportation, co‐generation, electric‐grid independent appliances, and space, aerospace, and military power applications. The range of bandgaps for achieving high conversion efficiencies using low temperature (1000–2000 K) black‐body or selective radiators is in the 0.5–0.75 eV range. Present high efficiency convertors are based on single crystalline materials such as In1−xGaxAs, GaSb, and Ga1−xInxSb. Several polycrystalline thin films such as Hg1−xCdxTe, Sn1−xCd2xTe2, and Pb1−xCdxTe, etc., have great potential for economic large‐scale applications. A small fraction of the high concentration of charge carriers generated at high fluences effectively saturates the large density of defects in polycrystalline thin films. Photovoltaic conversion efficiencies of polycrystalline thin films and PV solar cells are comparable to single crystalline Si solar cells, e.g., 17.1% for CuIn1−xGaxSe2and 15.8% for CdTe. The best recombination‐state densityNtis in the range of 10−15–10−16cm−3acceptable for TPV applications. Higher efficiencies may be achieved because of the higher fluences, possibility of bandgap tailoring, and use of selective emitters such as rare earth oxides (erbia, holmia, yttria) and rare earth‐yttrium aluminium garnets. As compared to higher bandgap semiconductors such as CdTe, it is easier to dope the lower bandgap semiconductors. TPV cell development can benefit from the more mature PV solar cell and opto‐electronic (infrared detectors, lasers, and optical communications) technologies. Low bandgaps and larger fluences employed in TPV cells result in very high current densities which make it difficult to collect the current effectively. Techniques for laser and mechanical scribing, integral interconnection, and multi‐junction tandem structures which have been fairly well developed for thin‐film PV solar cells could be further refined for enhancing the voltages from TPV modules. Thin‐film TPV cells may be deposited on metals or back‐surface reflectors. Spectral control elements such as indium‐tin oxide or tin oxide may be deposited directly on the TPV convertor. It would be possible to reduce the cost of TPV technologies based on single‐crystal materials being developed at present to the range of US$ 2–5 per watt so as to be competitive in small to medium size commercial applications. However, a further cost reduction to the range of US ¢ 35–$ 1 per watt to reach the more competitive large‐scale residential, consumer, and hybrid‐electric car markets would be possible only with the polycrystalline‐thin film TPV cells. ©1996 American Institute of Physics.