Following the detailed balance principle, we have systematically investigated the electricity generation from the infrared thermal radiation by 6.1 angstrom Sb-based converters. By simulating the converters in their possible single/multiple-junction configurations, the GaSb lattice-matched InAs0.91Sb0.09 alloy has been demonstrated not only to be an attractive converter for a broadband emitter operating at 1200-1500 K but also a potential subcell candidate to design high-performance tandem converters. To construct the tandem converters, it is shown that, for both mechanically-stacked and series-interconnected configurations, the GaInAsSb alloy's optimum bandgap E-g(o) dependence on the emitter temperature T-BB easily yields a quadratic equation E-g(o) = alpha T-BB(2) + beta T-BB + gamma with alpha, beta, and gamma the fitted structure-dependent parameters. These results provide some favorable guidelines to develop more powerful thermophotovoltaic devices. (C) 2015 Elsevier B.V. All rights reserved.