Silicon Heterojunction Solar Cells: Surface Passivation Quality on Large Area N Type and P Type Monocrystalline Silicon

23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain; 1441-1444
The aim of this work is to present our progress on heterojunction solar cells, based on a low temperature route using hydrogenated amorphous silicon (a-Si:H) ultrathin films deposited by PECVD on bulk crystalline silicon. We focus our work on both n-type and p-type monocrystalline silicon to achieve large area solar cells for industrial application. The analysis of the a-Si:H/c-Si interface quality is analyzed by the QSSPC technique that allows evaluating the passivation properties as well as qualifying the different steps. First, a new cleaning process is evaluated with respect to passivation properties, demonstrating that it is possible to obtain nearly as good passivation on textured as on polished samples with appropriate cleaning. An intrinsic layer is added to an emitter or BSF double side structure in order to show the impact of such a layer on passivation properties. Finally, full heterojunction solar cells have been characterised thanks to I-V measurements. Record Voc values up to 668 mV have been obtained on 5*5 cm² cells. Efficiencies of 16,2% and 15,8 have been obtained on P type and N type wafers, for cells of 5*5 cm² .