Owing to their elevated absorption coefficient, superior resistance to radiation and reduced effective electron mass, gallium antimonide (GaSb) semiconductors were documented to be suitable for photovoltaic systems applications. However, they were found to suffer from low efficiency. This work has been dedicated to enhance the design of GaSb based single-junction solar cells having window and back surface field made from AlGaAsSb material. The purpose is to maximize their electrical performance by considering doping and thickness of layers as design variables. A methodology of optimization was proposed. It is based on computer aided design through simulations performed under SILVACO-ATLAS software and a numerical procedure that was developed to achieve optimal design of this particular solar cell. The approach encompasses analysis of variance and derivation of response surface models to get explicit expression of the objective function corresponding to efficiency. The obtained results have shown an efficiency which is higher than all the previous known values established in literature.