Photovoltaic cells convert most of the absorbed photon energy to heat. Removal of the heat by thermal conduction creates a heat flux that is significant in concentrating photovoltaic (CPV) cells subject to high incident radiation flux. The Peltier effect interaction of this heat flux and the electrical current in the cell can either increase or decrease the temperature gradient within the cell. Here we show that the Peltier effect contributes to a measurable change in the temperature gradient in Ge-based CPV cells and therefore this effect should be considered in cell modelling. The effect may also have an impact on the temperature gradient of other photovoltaic cells and of other high power optoelectronic devices. (C) 2010 Elsevier B.V. All rights reserved.