Photoelectrochemical Water-Splitting Cells And Solar Cells Based On Si/Pedot Hybrid Core/Shell Nanowire Arrays

The use of solar cells and photoelectrochemical cells based on semiconductor materials which transform sunlight directly into two forms of energy-electricity and hydrogen are the most promising technologies, and may provide a low cost, environmentally safe and renewable resource instead of fossil fuels. In this paper, we focus on photovoltaic devices and water-splitting photoelectrodes based on Si/Poly (3,4-ethylenedioxythiophene)(PEDOT) hybrid core/shell nanowire arrays. Meanwhile, We also pay attention to explore the mechanism of nano-size effects and interface effects on the separation, transport and recombination of carriers in the nanostructured devices. The main results are summarized as follows:(1) The Si/PEDOT core/shell nanowire arrays with a high aspect ratio are successfully fabricated simply and effectively by silver-assisted chemical etching method and vapor phase polymerization processes. Our results show that the PEDOT film can conformally coat the Si nanowire arrays and the core/shell hybrid structures significantly suppresses the reflectance to below1%over a wide spectrum from300to1100nm.(2) We study the Si/PEDOT core/shell nanowire arrays as hybrid photoanodes for photoelectrochemical water-splitting. The PEDOT layer is employed as a multi-functional coating to prevent photocorrosion of Si nanowires, collect photogenerated holes and catalyze the water oxidation reaction. The amino silane modified Si nanowire surface improves PEDOT layer adhesion, and the resulting photoanode exhibits better photoresponse and improved stability. By tuning the length of nanowires, we identify that the competition between the carrier recombination and catalytic water oxidation reaction is the primary factor determining photoelectrocatalytic activity of the hybrid photoanode.(3) We also investigate in great detail the hybrid solar cells based on the organic/inorganic Si/PEDOT core/shell nanowire arrays (SiNWs/PEDOT). The hybrid cell shows that the performance is improved greatly and an excellent power conversion efficiency of3.23%is achieved, which is as seven times as large as that of the planar cell without the nanowire structure. In addition, the studies of the reflectance, the I-V curve and the external quantum efficiency show that the great enhancement of performance for the SiNWs/PEDOT cells is due to the fact that the Si/PEDOT core/shell nanowire structure is successfully fabricated by vapor phase polymerization method, resulting in a high light trapping effect, a large junction area and an enhancement of the carrier collection efficiency.