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Passivation of Silicon Surface for Gr-Si MIS Solar Cell- A project carried out by Prof. Sukruti Kaulgud, Assistant Professor, Department of Electronics and Telecommunication, Thakur College of engineering and Technology, Mumbai at NCPRE under PUMP

In wireless sensor network (WSN), energy conservation is the biggest challenge. Energy harvesting is at the core of energy conservation and this is where Solar cell becomes the most preferred option. Applications in WSN requires solar cells to be highly efficient with smaller dimensions and easy on budget. Graphene promises to be an effective solar cell material addressing both these requirements. Metal-Insulator Semiconductor structure of Graphene-Silicon solar cells shows enhanced efficiency over Schotttky Junction solar cells. However, small size solar cell using Graphene as one of the electrodes is not providing higher power conversion efficiency. This is where interface tailoring provides us with more avenues to improve efficiency.

To further boost the efficiency, Graphene Oxide (GO) could be the panacea on the required criteria. Also, inclusion of RCA Oxide layer between Silicon and the electron blocking layer, attributes to the dangling bond saturation which results in reduced interface defects.

To further improve efficiency P3HT and TIPS Pentacene were investigated. A simulation model was developed to investigate their passivation abilities. It was clear that, TIPS pentacene gives better passivation of Silicon surface. The average open circuit voltage (Voc) of the MIS silicon solar cell with TIPS pentacene is higher than that with P3HT and GO. The minority carrier lifetime also enhances. Dangling bonds that were present at the silicon surface were an impediment to improving efficiency to a higher level. Modifying Silicon surface with RCA oxide address this issue. The interfacial layer with a combination of GO + RCA, P3HT + RCA and TIPS pentacene + RCA modifies the Si surface for better passivation. The optimum thickness of the interfacial layer, provides enhanced Voc and minority carrier lifetime.

The work can be extended by adding Graphene layer with optimum doping and antireflection coating to further boost PCE. These solar cells provide the advantage of low cost, ambient temperature fabrication process, and hence are more appealing for large scale production. On the lines of introducing new interfacial layers, the future work can explore introducing newer materials. A slightly different scope can also be explored by considering different solar cell structures beyond the one considered here namely MIS solar cell.

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