The Fraunhofer ISE has developed a characterization tool called spectrometric characterization. In this paper we discuss that this tool is extremely powerful to characterize triple-junction (3J) EOL cells. The current-mismatch of the subcells can be determined and the performance for current-matched subcells can be predicted. Additionally, lattice-matched AlGaInP/GaInP/AlGaInAs/GaInAs/Ge quintuple-junction (5J) cells are being developed at Fraunhofer ISE as a possible next-generation of space solar cells. This material combination aims at the same BOL efficiency as state-of-the-art 3J cells but higher EOL efficiency. Based on spectral response measurements it will be demonstrated that the 5J cells do in fact show a higher radiation hardness compared to the 3J cell.

Fraunhofer ISE and RWE SSP have developed a lattice-matched GaInP/GaInAs/Ge triple-junction space solar cell with a begin-of-life efficiency of 28.0 % (AM0, 1367 W/m, T=28°C) and excellent remaining factors of 90.5% after 5x10 and 86.6% after 1x10 1 MeV electron irradiation per cm. This was accomplished by systematic optimisation of the middle cell design for maximum end-of-life performance. This new triple cell, the RWE3G-28%, constitutes the second generation of fully European triple-junction space solar cells which is now going into qualification. Future concepts such as light weight solar cells, five and six-junction cells and the use of metamorphic materials are under investigation.

A programme for the development of advanced triple-junction solar cells in Europe was initiated and supported by ESA and DLR. RWE Solar (D) lead a research consortium including FhG-ISE (D), CESI (I), University of Paris (F) and Astrium. (D). The paper presents first results of several types of lattice-matched and lattice-mismatched triple junction solar cells achieving AMO-efficiencies beyond 24%. Additionally, the pre-development of the next generation of space solar cells with efficiencies above 30% is described.

Purpose of this work is the testing of materials and manufacturing processes able to withstand the high temperature conditions typical of the interplanetary space missions towards the Sun (e.g. Mercury). This goal was achieved by means of an optimisation work performed on the space solar cells already existing and "standard" photo-voltaic assembly technologies.After some preliminary tests and analyses the most suitable candidates have been identified for all the mission phases and different CICs and modules design have been established. The paper presented at the 29(th) PVSC conference described the preliminary trade offs and experimental activities.More than 100 CICs in various configurations and 7 modules have been manufactured to find out the best high temperature and insolation PVA concept (solar cell candidates SJ TJ; substrate candidates: Carbon & Aluminium substrates).