Abstract
A graphene/Si Schottky junction solar cell is commonly fabricated by using the top-window structure. However, reported devices have many drawbacks such as a small active area of 0.11 cm2, s-shape in the J-V curves, recombination process of charge carriers at the graphene/textured Si interface, high cost and a complex fabrication process. Here, we report a novel graphene/Si Schottky junction solar cell with a back contact-structure, which has benefits of a simpler fabrication process, lower fabrication cost, and larger active area in comparison with a device fabricated with the previous structure. Additionally, we found that the PMMA residue left on graphene surfaces is the key to eliminate the s-shape in the J-V curves. Thus, the deep UV treatment of the CVD graphene is applied within the wet transfer process to effectively remove the PMMA residue, suppress the behavior of s-shaped kink in J-V curves and enhance the solar cell efficiency. As a result, the recorded power conversion efficiency of 10% is achieved for graphene/textured Si devices without chemical doping and anti-reflection coating, and this value is improved to 14.1% after applying chemical doping. Doped devices also show great stability and retain 84% of the efficiency after 9 days storage in air.
Highlights
The attractive properties of graphene, such as near-zero bandgap, high electrical conductivity, high mobility, flexibility, and high transparency have stimulated a lot of research interest [1]
The deep UV (DUV) treatment for 20 min in our previous work as shown in Fig. 1c was applied before removing the PMMA layer in order to effectively remove the PMMA layer with less residue [23]
S1a, S1b and S1c in supporting information). This means that the number of photons absorbed is higher and leads to an increase in the solar cell efficiency as confirmed by the external quantum efficiency data described later
Summary
The attractive properties of graphene, such as near-zero bandgap, high electrical conductivity, high mobility, flexibility, and high transparency have stimulated a lot of research interest [1]. Suhail et al / Carbon 129 (2018) 520e526 reducing the PMMA residue and enhancing p-doping in graphene using a forming gas treatment with a specific mixed ratio (Ar/H2 (50:50)) at 400 C Using this procedure Song et al [4] found that there was still an s-shape in the J-V curves of devices treated with the forming gas at 350 C for 2 h, and it was stated that this issue could be eliminated by applying the optimal native oxide of Si substrates [4]. It has been reported [18e20] that the forming gas treatment does not remove the PMMA residue properly. The chemical doping is employed to further improve the solar cell efficiency
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