The experimental U-I characteristics of a single GaSb cell, a single Si cell and their modules in a TPV system using a SiC radiator were investigated. The influence of the radiator temperature and the radiator-cell distance on the output performances of a single cell and its module was analyzed. The results demonstrate that increasing the radiator temperature or decreasing the radiator-cell distance both lead to the increasing the short-circuit current density and the output power density, but the open-circuit voltage decreases because of the rise of the cell temperature. The maximum output power densities of a single GaSb cell and the corresponding module are 0.26 and 0.28 W/cm(2), respectively, which are approximately 4.3 and 6.0 times that of a single Si cell and its module for a combustion power of 4.2 kW and a radiator-cell distance of 1.1 cm. Furthermore, a mathematical physical model was constructed to analyze the influence of the cell temperature on the output performance of the cells. For a given radiator temperature and radiator-cell distance, the theoretical results indicate that the output power density decreases with cell temperature because of attenuation of the open-circuit voltage. (C) 2011 Elsevier B.V. All rights reserved.