In this thesis, a simulated annealing algorithm is implemented to optimize the efficiency of a tandem solar cell. The efficiency of a tandem solar cell is approximated by the current of the tandem solar cell. This current is determined by the simulation program GenPro4. Firstly, the general concepts of simulated annealing is described. After understanding these concepts, a simulated annealing algorithm is implemented for our specific problem. This algorithm includes the handling of discrete variables which describe the structure of the solar cell. The results contain multiple variants of the newly implemented simulated annealing algorithm, which differ in the used temperature schedule. Finally, a conclusion is made that a temperature schedule with a slower convergence gives the best results. However, one should consider a slightly faster convergence whenever there is a need to reduce the computational time. Moreover, one should write their own implementation of a simulated annealing algorithm when dealing with discrete variables, thus not use the provided function of MATLAB.