A global optimisation of AlGaAs/GaAs solar cells under light with different angles of incidence is carried out in this work. Not only are the optimum internal and external device structures calculated, but also the thicknesses of the anti-reflecting coatings layers. For this reason, a study of the whole structure is carried out from a global point of view taking state-of-the-art technology into account. In fact, this kind of work has not been carried out up till now. The best structure, working at 1000 suns (100 W/cm(2)), reaches an efficiency of 28.8% for normal incidence of light. This efficiency is nearly constant up to an incident angle of around 60 degrees and it then sharply decreases for higher angles. Variations of parameters that can be optimised (thicknesses and doping levels) as a function of angle of incidence ranging from 0 degrees to 90 degrees are presented. Deviations from the optimum structure are also analysed with the purpose of determining their influence in the solar cell manufacturing process.