30% monolithic tandem concentrator solar cells for concentrations exceeding 1000 suns

Results of a cost study for concentrator systems are discussed. In this context it is concluded that high-concentration and high-efficiency solar cells are beneficial for lowering the cost of PV produced energy. MOVPE-grown Ga_0.35P/Ga_0.83In_0.17As monolithic tandem cells are developed for the application in such high-concentration systems. These solar cell structures are grown lattice mismatched on GaAs substrates. An efficiency of >31 % at 300× AM 1.5D and around 30 % at a 1000× concentration was measured. An all-glass test module with an aperture area of 64 cm² was built up and showed an efficiency of >24 % measured under outdoor conditions. The module has a geometrical concentration factor of 123. This result can be further improved by increasing the concentration ratio and optimizing the cell structure