This paper presents several numerical simulations to obtain an optimized model for AlGaAs-GaAs solar cell, using the TCAD simulator of Sentaurus. First an updated review of the state of the art in the development of GaAs solar cell is provided, with emphasis on the AlGaAs-GaAs cells. Secondly, a set of theoretically derived characteristics is given for this type of solar cells. Then, a comparison between two solar cell architectures is considered, one with a full metalized back contact and other with a back contact of 5μm. To resolve the optical and electrical characteristics of the solar cell, some methods can be used by TCAD Sentaurus. The transfer matrix method (TMM) and the Raytracing approach are implemented to solve the optical part of the cell. Instead, for the electrical part, the resolution of the semiconductor equations, principally the Poisson equation, was computed. At the end of the work an optimization phase of the solar cell was made, in order to search the technological parameters leading to optimal performances of the cells, the effects of the doping level and the thicknesses of the base, bsf and emitter layers were also investigated.