PASSIVATION PROPERTIES OF AMORPHOUS AND MICROCRYSTALLINE SILICON LAYERS DEPOSITED BY VHF-GD FOR CRYSTALLINE SILICON SOLAR-CELLS

A comparative study of crystalline silicon (c-Si) surface passivation techniques is presented. The passivation is essential in increasing the total solar cell efficiency by enhancing the open-circuit voltage (V-oc). Apart from the thermally grown oxides or nitrides widely used sofar, recent publications report on excellent passivating properties of amorphous silicon (a-Si:H)- and microcrystalline silicon (mu c-Si:H) layers, deposited on n-type crystalline silicon [1-3], forming thereby heterojunctions. We present first results of a new structure called ((BAP (Both Sides Amorphous Passivated) cell)), where the wafer was sandwiched between two intrinsic amorphous silicon layers. These two layers, as well as the mu c-Si:H emitter, and the layer forming the BSF (Back Surface Field) were all deposited by the VHF-GD (Very High Frequency Glow-Discharge) process which was developed in our laboratory [14]. BAP cells showed V-oc-values as high as 635 mV, proving thus the excellent passivating properties of a-Si:H and the validity of this cell concept which makes a fully in-line processing possible (wafer in-cell out).