Efficient, economic & mass-reduced solar cells 

The current state-of-the art solar technology is based on the ‘lattice-matched’ GaInP/ GaInAs/Ge triple-junction solar cell. Worldwide, there are three major manufacturers of space solar cells based on III-V semiconductors, with Europe’s Azur Space GmbH in competition with the US Emcore and Spectrolab. The development process involves improvements and fine-tuning of the structure, which lasts more than 10 years. The maximum practically achievable efficiency for space is 30% at the beginning of life and 25% at end of life. In 2003 Fraunhofer ISE and RWE SSP realised the first generation of fully European triple-junction space solar cells in the RWE-27% class, with a second-generation RWE-28% following in 2009 being employed by missions including Alphabus and Galileo. The current third generation RWE-30% class represents the final stage of lattice-matched triple junction solar cell technology. The next generation will target cost and mass reduction, and push efficiency up to 33%, with new technologies under study including lattice-matching on germanium, lattice mismatching, quantum cells and thin cells.