Duration: 12 months
Currently, the high material usage for space solar cells is caused by three main levers: 1. The germanium substrate, 2. the epitaxy process and 3. the microfabrication of cells. In order to reach “Green Space” targets to severely reduce the environmental impact of space missions on earth, a massive reduction of resource consumption is needed in all three areas. Recent research to reduce this is based on more efficient epitaxy (e.g. in the German BMWK funded project H2Demo) and on substrate re-use e.g. via porous germanium. However, microfabrication is not really tackled yet for space solar cells. Material efficient technologies are available in silicon solar cells production. However, the requirements for space solar cells usually prevent their implementation, as some crucial materials in these technologies are not space compatible. The thin film solar cells investigated in “AlternateSpace” with revolutionary mask and plate metal contacts can be a game-changer here: the need of the critical materials, e.g. contact metals and some process chemicals can be reduced by 90-95%- i.e. a factor of 10-20. Developments in epitaxy and substrate re-use target a resource reduction by a factor of 2-5 – in other words, in case of success AlternateSpace will severely decrease the influence of the microfabrication process as compared to the other 2 levers. First steps were taken towards material-efficient microfabrication processes such as screen printing for III-V solar cells, e.g. in the German project “SALLI”. However, they are not suitable for space solar cells currently as the used metals pastes contain polymers and the plating was realized with copper and nickel – materials that cannot easily be used in space. This project thus aims towards an innovative mask-and-plate approach to microfabricate thin film space solar cell without the use of photolithographical or metal evaporation steps with BOL efficiency >30%.
