Nanocrystalline Silicon Carrier Collectors for Silicon Heterojunction Solar Cells and Impact on Low-Temperature Device Characteristics

Silicon heterojunction solar cells typically use stacks of hydrogenated intrinsic/doped amorphous silicon layers as carrier selective contacts. However, the use of these layers may cause parasitic optical absorption losses and moderate fill factor (FF) values due to a high contact resistivity. In th...

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Bibliographic Details
Published in:IEEE journal of photovoltaics 2016-11, Vol.6 (6), p.1654-1662
Main Authors: Nogay, Gizem, Seif, Johannes Peter, Riesen, Yannick, Tomasi, Andrea, Jeangros, Quentin, Wyrsch, Nicolas, Haug, Franz-Josef, De Wolf, Stefaan, Ballif, Christophe
Format: Article
Language:English
Subjects:
Carrier transport
Contact resistance
contact resistivity
Heterojunctions
nanocrystalline silicon
Photovoltaic cells
Schottky barrier
Silicon
silicon heterojunction (SHJ)
solar cells
Temperature dependence
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Summary:Silicon heterojunction solar cells typically use stacks of hydrogenated intrinsic/doped amorphous silicon layers as carrier selective contacts. However, the use of these layers may cause parasitic optical absorption losses and moderate fill factor (FF) values due to a high contact resistivity. In this study, we show that the replacement of doped amorphous silicon with nanocrystalline silicon is beneficial for device performance. Optically, we observe an improved short-circuit current density when these layers are applied to the front side of the device. Electrically, we observe a lower contact resistivity, as well as higher FF. Importantly, our cell parameter analysis, performed in a temperature range from -100 to +80 °C, reveals that the use of hole-collecting p-type nanocrystalline layer suppresses the carrier transport barrier, maintaining FF s in the range of 70% at -100 °C, whereas it drops to 40% for standard amorphous doped layers. The same analysis also reveals a saturation onset of the open-circuit voltage at -100 °C using doped nanocrystalline layers, compared with saturation onset at -60 °C for doped amorphous layers. These findings hint at a reduced importance of the parasitic Schottky barrier at the interface between the transparent electrodes and the selective contact in the case of nanocrystalline layer implementation.
ISSN:2156-3381
2156-3403
DOI:10.1109/JPHOTOV.2016.2604574