**4. Conclusions**

Chlorination/alkylation process was used to graft different molecules on the Si NWs. The methyl provided the highest coverage (100%) among all of the alkyl molecules (50–70%). We show different parameters that affect the stability of the molecules on the surface: molecular coverage, chain length, types of bond interactions, surface energy, and Si NW diameter. However, the propenyl (CH3▬CH〓CH▬ Si NWs) showed excellent surface oxidation resistance: very small amount of oxides forming after more than 2 months of exposure to ambient air. Studies on the H-terminated Si NW oxidation kinetics revealed that their thermal stability relies strongly on the temperature. At lower temperatures, initially Si▬Si backbond oxidation. At higher temperatures, oxygen diffusion is considered to be the initial rate-determining step, as it controls the growth site concentration.

We show that the molecules affect the solar cell performance, and a proper molecular may lead to superior solar cell performance. For instance, Si NW attached to CH3 shows higher performance than oxide surface (by factor of four). This is attributed to the low surface recombination, low defects, and efficient charge transfer at the heterojunction. All these can be achieved by grafting a molecule of the surface. This type of heterojunction is used in advanced solar cell configurations and still under review.

#### **Acknowledgements**

This work was supported by a MAOF Grant from the Council for Higher Education in Israel for new faculty members. Dr. P. Natarajan is thankful for *Heterojunction-Based Hybrid Silicon Nanowires Solar Cell DOI: http://dx.doi.org/10.5772/intechopen.84794*

the SEEDER scholarship for postdoctoral students. Awad Shalabny and Sumesh Sadhujan are appreciative of the institutional scholarships for PhD students they received from Ben-Gurion University of the Negev.
