Comparison of Nanocarbon–Silicon Solar Cells with Nanotube–Si or Graphene–Si Contact

Nanocarbon structures such as carbon nanotubes (CNTs) and graphene (G) have been combined with crystalline silicon wafers to fabricate nanocarbon-Si solar cells. Here, we show that the contact between the nanocarbon and Si plays an important role in the solar cell performance. An asymmetrically configured CNT-G composite film was used to create either CNT-Si dominating or G-Si dominating junctions, resulting in obviously different solar cell behavior in pristine state. Typically, solar cells with direct G-Si contacts (versus CNT-Si) exhibit better characteristics due to improved junction quality and larger contact area. On the basis of the composite film, the obtained CNT-G-Si solar cells reach power conversion efficiencies of 14.88% under air mass 1.5, 88 mW/cm2 illumination through established techniques such as acid doping and colloidal antireflection. Engineering the nanocarbon-Si contact is therefore a possible route for further improving the performance of this type of solar cells.