Recent Progress on the CEA-INES Heterojunction Solar Cell Pilot Line

Abstract

In this paper we present progress made during 2014/2015 on the heterojunction (HJ) solar cell pilot line (LabFab), located at the French National Solar Energy Institute (INES) and operated by the French Alternative Energies and Atomic Energy Commission (CEA). After an optimization phase a production capability of 1100 cells/hour was demonstrated end of 2013 with an average efficiency of 20.11%. Currently, the production LabFab baseline has been increased to 20.53% (rear emitter, 4 bus-bar, 156mm pseudo-square (156 PSQ), 240 cm2, bifacial cells). This was obtained by optimizing substrate selection, thermal donor anneal (TDA), cell texturing without IPA and hydrogenated amorphous silicon layer deposition on monocrystalline silicon (a-Si:H/c-Si). The latter by optimization of hydrogen plasma steps, fine tuning of the silane to hydrogen dilution and correct management of thermal aspects of the deposition process (PECVD). LabFab production flow has given cell efficiency of 21.08% using high mobility indium tin oxide (ITO) and cell insulation without laser opening. Greater than 5Wp cells were selected for integration into 60-cell modules. A certified record of 308Wp has been achieved with a cell-to-module ratio of 100.7%. Cells were selected and finished as monofacial cells with a rear side silver layer and a second antireflective coating on the front side, leading to an industrial record cell of 22.2% at CEA-INES. Finally, it is shown that rear-side ITO with edge exclusion is an excellent solution for HJ cell insulation, with outstanding reliability on the modules. Edge exclusion was obtained by deposition through open pockets on a production-ready equipment, allowing a short term LabFab perspective of above 21% cells at 1500 wafers per hour and a module performance baseline over 300Wp.