Abstract
We show that a sponge-like structure of interconnected Si nanowires embedded in a dielectric matrix can be obtained by laser annealing of silicon rich oxides (SRO). Due to quantum confinement, the large bandgap displayed by these percolated nanostructures can be utilized as a tandem stage in 3rd generation thin-film solar cells. Well passivated by the SiO₂ dielectric matrix, they are expected to overcome the difficulty of carrier separation encountered in the case of isolated crystalline quantum dots. In this study PECVD grown SRO were irradiated by a cw Ar⁺ laser. Raman spectroscopy has been used to assess the crystallinity of the Si nanostructures and thus to optimize the annealing conditions as dwell times and power densities. In addition, Si plasmon imaging in the transmission electron microscope was applied to identify the sponge-like structure of phase-separated silicon.
Highlights
Silicon based solar cells have been studied extensively due to their low cost, the efficiency of a single junction solar cell is relatively small and is restricted to the ShockleyQueisser
We show that a sponge-like structure of interconnected Si nanowires embedded in a dielectric matrix can be obtained by laser annealing of silicon rich oxides (SRO)
Spinodal decomposition of metastable Si-rich oxides is a promising synthesis process for the formation of crystalline Si sponge-like structures. These structures can be used in a multi-junction approach, to improving the single bandgap silicon solar cell efficiency with the incorporation of larger bandgap nanocrystalline Si structures onto the solar cells, allowing a larger spectral coverage
Summary
Silicon based solar cells have been studied extensively due to their low cost, the efficiency of a single junction solar cell is relatively small and is restricted to the ShockleyQueisser. Spinodal decomposition of metastable Si-rich oxides is a promising synthesis process for the formation of crystalline Si sponge-like structures These structures can be used in a multi-junction approach, to improving the single bandgap silicon solar cell efficiency with the incorporation of larger bandgap nanocrystalline Si structures onto the solar cells, allowing a larger spectral coverage. We propose an alternative method for obtaining crystalline Si sponge-like nanowires in SiO2 by laser processing of silicon rich oxide (SRO) thin films to be used as a tandem cell element. We demonstrate the formation of sponge-like Si in PECVD grown SRO films by cw laser annealing This structure is interesting due to the nearly perfect passivation in a SiO2 matrix which makes it ideal for carrier transport in thin film solar cells
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