| 研究実績の概要 |
Although heterojunction silicon solar cells show high efficiency, their low heat resistance and optical losses at the passivation layer hinder further efficiency improvement.
The aim of this work is the fabrication of a simple p-type contact structure that overcomes these issues and combines simultaneously high passivation quality and low contact resistivity. For this purpose, the stack of a very thin oxide layer and a doped layer with crystalline phase is considered.
As the material for the oxide layer, Al2O3 deposited by atomic layer deposition and SiOx grown with peroxide solution were adopted. For the p-layer, p-μc-Si:H and p-μc-SiOx:H, both fabricated by plasma CVD method, were chosen.
It was found that p-layers with lower crystallinity show higher passivation effect, despite their lower thicknesses. Additionally, the p-layer crystallinity tended to increase with thickness. Besides, it was shown that the passivation quality of the SiOx/p-μc-SiOx:H stack could be further improved by applying an additional annealing process after the deposition, achieving a minority carrier effective lifetime higher than 200 us, the highest among the fabricated samples. This suggests that the crystalline silicon surface was partially passivated by hydrogen diffused from the amorphous phase of the p-layer. Furthermore, a relatively low resistance was achieved with the same stack.
These results indicate that this approach is promising for the realization of a simple p-type contact that possesses both low contact resistance and high passivation quality for crystalline silicon solar cells.
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| 今後の研究の推進方策 |
In addition to the lacking contents from the initial year, the p-type contact design will be reconsidered including the combination with the transparent conductive oxide layer required for the solar cell device. Additionally, feedback through the fabrication of solar cells will be carried out to optimize the contact structure. Finally, device simulation is planned to get a better insight into the carrier transport mechanism within the considered structure.
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