p-Type Cu2O/PEI modified Si-Nanowires for Efficient Liquid Junction Solar Cells

Pathak, Saurabh Kumar (2021) p-Type Cu2O/PEI modified Si-Nanowires for Efficient Liquid Junction Solar Cells. Project Report. IITHyderabad, IIT Hyderabad.

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Abstract

This work aims at fabricating an efficient liquid junction silicon nanowire solar cell and investigate their photovoltaic performance. Here, p-type Cu2O is used as a hole conductive material and is synthesized using the hydrothermal method. The silicon nanowires are etched on an n-Si wafer using metal-assisted chemical etching, and to avoid agglomeration, they are treated with 5% HF. The carbon fabric is used as a counter electrode due to its stability and high conductivity instead of previously reported Pt metal as a counter electrode which was very expensive. 0.05 M HBr and 8.6 M Br2 mixture is used as a redox solution. In the case of SiNW, the efficiency obtained was 5.04% which is attributed to the light trapping properties of SiNW, and also in the case of Cu2O microcrystals decorated SiNW, the efficiency obtained was 5.08% which is almost the same as in the case of SiNW this can be explained by the fact that the HOMO of Cu2O is not aligned properly to act as hole conductor but as soon as the Cu2O@SiNW is further coated with PEI polymer the efficiency increases by about 50% which can be explained by the fact that as the Cu2O microcrystals are decorated with PEI polymer, it decreases its work function and due to which its HOMO come above the HOMO of the SiNW and it acts as hole conducting material. In previous reports, metal nanoparticles, i.e., Pt and Au, are used over SiNW act as electron trappers, but PEI decorated SiNW act as hole conductor, due to which the recombination rate decreases and overall performance of the cell increases. The hole conducting property of PEI@Cu2O can be proved by the fact that in the case of Cu2O@SiNW, the efficiency is 5.08%, same as in the case of pristine SiNW, but in the case of PEI@Cu2O@SiNW, the efficiency is 7.65%, about 1.5 times increase in efficiency is observed. Various characterization including optical, structural, impedance studies, PEC are performed to understands the phenomenon deeply, which is involved in improved performance of PEI@Cu2O@SiNW photoanode.

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