An approach for improving the carriers transport properties of a-Si:H/c-Si heterojunction solar cells with efficiency of more than 27%

摘要

The carrier transport properties at the interfaces are crucial factors that influence the efficiency of a-Si:H/c-Si heterojunction solar cells. The interfaces transport properties of carrier were analyzed and discussed by simulating the influence of band offsets and the work function of transparent conductive oxide (TCO) on the energy band structure, distribution of carrier and interfaces recombination with AFORS-HET program. The results reveal that the interfaces transport quality of carrier and the performance of solar cells are strongly affected by the work function of TCO and the band offsets at a-Si:H/c-Si hetero-interface, besides the interface defects and defect states in a-Si:H. When the valence band offset at p-type a-Si:H-type interface was under 0.37 eV, the work function of TCO for TCO/p-type a-Si:H interface was controlled above 5.2 eV, and the valence band offset at n-type c-Si/BSF interface for the back surface field (BSF) was about 0.37 eV, the interfaces recombination decreased to a minimum value and the photoelectric conversion efficiency of the textured TCO/p-type a-Si:H/i-type a-Si:H-type c-Si/i-type a-Si:H~+-type a-Si:H/Al solar cell could even reach 27.37% (V_(oc): 805.5 mV, J_(sc): 41.85 mA/cm~2, FF: 81.2%) by simulation. An in-depth understanding of the interfaces transport properties can help in decreasing the interfaces recombination and improving the efficiency of solar cells.