THE EFFECT OF INTERPOSING NANOCRYSTALLINE Si(B) P+ LAYER ON THE PHOTOVOLTAIC PROPERTIES OF a-Si: H TANDEM SOLAR CELLS

摘要

Tandem amorphous silicon solar cells have attracted extensive interest because of better performance than single junction counterpart. As n/p junctions play an important role in the current transportation of tandem solar cells, it is important to design and fabricate good n/p junctions. The properties of the n/p junction of amorphous silicon (a-Si) were studied. We investigate the effect of interposing a nanocrystalline p+ layer between n (top cell) and p (bottom cell) layers of a tandem solar cell. The crystalline volume fraction, the band gap, the conductivity and the grain size of the nanocrystalline silicon ( nc-Si) p+ layer could be modulated by changing the deposition parameters. Current transport in a-Si based n/p (‘‘tunnel’’) junctions was investigated by current-voltage measurements. The voltage dependence on the resistance (V/J) of the tandem cells was examined to see if n/p junction was ohmic contact. To study the affection of different doping concentration to the properties of the nc-Si p+ layers which varied the properties of the tunnel junctions, three nc-Si p+ film samples were grown, measured and analyzed.