Layer-separated treatment accelerating growth of P-type hydrogenated nanocrystalline silicon in SHJ cells

Abstract

Doped nanocrystalline silicon has higher conductivity and lower parasitic absorption than doped amorphous silicon when used in photovoltaic heterojunction cells, which has been demonstrated in many previous studies. In this paper, the growth mechanism of p-type hydrogenated nanocrystalline silicon (p-nc-Si:H) thin films as doped emitter layer of silicon heterojunction (SHJ) solar cells is researched. Firstly, we focused on the effect of different PECVD deposition conditions on the growth rate and rapid crystallization of p-nc-Si:H given the frequency of 13.56 MHz, such as gas flow during deposition, chamber pressure, and power-density. We find that solar cell performs worse if deposition rate of p-nc-Si:H is dramatically increased. Then, we create layer-separated treatment method that balances growth rate and film quality through layered growth at different power levels. Finally, we designed layer-separated treatment for fast deposition rate of 2.11 Å/s with high crystallinity, then realized SHJ cell whose efficiency reached 25.88 %.