This paper presents the numerical modeling and optimization of a spectrum splitting photovoltaic thermoelectric (PV-TE) hybrid system. In this work, a simulation model is established in consideration of solar concentration levels and several heat dissipation rates. Exemplarily, the performance of a hybrid system composed of a GaAs solar cell and a skutterudites CoSb3 solar thermoelectric generator (TEG) is simulated. Analysis under different conditions has been carried out to evaluate the electrical and thermal performance of the hybrid system. Results show that the cutoff-wavelength of the GaAs-CoSb3 hybrid system is mainly determined by the band gap of solar cell, when the solar concentration ratio is ranged between 550 to 770 and heat transfer coefficient h = 3000-4500 W/m(2) K, the hybrid system has good electrical performance and low operating temperatures. Based on the analysis of the GaAs-CoSb3 hybrid system, guidelines for the PV-TE system design are proposed. It is also compared with a PV-only system working under the same cooling condition; results show that the PV-TE hybrid system is more suitable for working under high concentrations. (C) 2012 Elsevier Ltd. All rights reserved.