Optimization of Interdigitated Back Contact Silicon Heterojunction solar cells (IBC-SiHJ)

Abstract

This study deals with the development and optimization of Interdigitated Back Contact (IBC) Silicon Heterojunction(HJ) solar cells based on n-type crystalline silicon (c-Si)substrates. Interdigitated back contact silicon heterojunction (IBC-SHJ) solar cells have the potential for high open circuit voltage (VOC) due to the surface passivation and heterojunction contacts, and high short circuit current density (JSC) due to all back contact design. Intrinsic amorphous silicon (a-Si:H) buffer layer at the rear surface improve the surface passivation hence VOC and JSC, but degrade fill factor (FF) from an “S” shape J-V curve. Two-dimensional (2D) simulation using “Silvaco-ATLAS” demonstrates that the low FF is related to the valence band offset (energy barrier) at the hetero-interface. Two approaches to improve the efficiency are evaluated: (1) modify the contact spacing, (2) reduce the gap region (width between BSF and emitter). The influence of these parameters has been tested by generating the current-voltage (I-V) curves under AM1.5 illumination, and so extract the output characteristics, namely the open circuit voltage (VOC), as well as the short-circuit current density (JSC), the fill factor (FF) and the conversion efficiency η of the cell.