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Solar energy conversion applications based on onedimensional nanostructure array

Solar energy conversion applications based on onedimensional nanostructure array
Jung-Ho Lee
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Solar power has been taken into account as one of the most important and clean sources of renewable energy. However, solar energy currently provides only a small amount of global energy production due to expensive cost of electricity generation. Nowadays fabrication of nanostructured Si for light trapping and conversion becomes fascinating and promising in conventional solar devices. Light photons can be trapped by semiconductor materials and created free electrons and holes, which can be separated by the junction between two different materials and then collected to power the external circuit. Because of higher light anti-reflectance, faster carrier transportation, and easy fabrication process, nanostructure, especially one-dimensional structure, has obvious advantages and bright future in solar energy conversion. We reported that Ag-assisted chemical etching method is capable of fabrication porous Si from amorphous Si. The porous Si nanostructure will be fabricated after controlled condition etching, for example, HF and H2O2 concentration, Ag deposition time and etching time. We have studied etching mechanism and found that a-Si etching mechanism is distinct from the one on crystalline silicon. The pores in nanostructure increased with HF and H2O2 concentration. Besides, higher concentration may lead to a more bent nanoholes inside. Fabrication and characterization of SiNWs/PEDOT: PSS hybrid solar cells with different length of nanowire array were described in this study. A remarkable PCE of 10.05% was obtained by optimizing the etching time to 30s, which correspond to an average 146-nm-length of nanowire array. The SEM images of SiNWs/PEDOT: PSS solar cell samples revealed that the sample of 30s etching held a better hetero-junction between SiNWs array and the polymer, as a result that its FF achieved to the highest value among all samples, and both its J-V and EQE curves tend to an ideal result. With the increase of SiNWs length, the recombination of minority carriers is rising up, which can lead to a lower efficient photocurrent and then a worse J-V photovoltaic characterization Well-ordered granular Si nanopillar arrays were synthesized by a novel etching method combined two step Metal-Assisted chemical etching. The granular SiNP exhibits a well porosity structure with larger Si partials and interspaces, which are beneficial to increase the specific surface area of Si cathode. Thereby, compared to the conventional SiNPs, a better contact between Si cathodes with electrolyte enhanced the photoelectrochemical performance, including a higher photocurrent, which enable to obtain a high photocurrent (27.5 mA/cm2 at 0V vs. RHE), and to be enhanced by ~10%. In addition, a positive shifted ~240mV was obtained using granular SiNP array structure.
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