Enhanced near infrared light trapping in Si solar cells with metal nanowire grid front electrodes

This work focuses on the optical performance of silver nanowire grids as front solar cell electrodes in a realistic dielectric environment. To do so, we first demonstrate the successful integration of the metallic grids on an ITO-free c-Si solar cell with arbitrarily high nanowires by light-induced electroplating in nano-imprinted polymer masks. The bottom-up approach enables the fabrication of high-aspect ratio grids with estimated very low sheet resistance (<2Ω⋅□) and high transparency (>95%). We use tunnel oxide passivating contact (TOPCon²) silicon cells as a platform to probe the grid's transparency. External quantum efficiency maps together with optical simulations reveal that the grids’ transparency in the visible spectral range is greater than expected from geometrical shading due to the sub-wavelength cross-section of the metal nanowires. On top of that, the nanowire grid even enhances the photocurrent at the near infrared, as a result of the increased optical path length from the grid's diffraction. Lastly, we demonstrate that the cell's photocurrent is unaffected by the angle of illumination up to about 40°, which is the relevant range for encapsulated cells in solar panels. Our findings highlight the dual role of metal nanowire grids as both electrical conductors and optical enhancers, offering substantial potential for future photovoltaic technologies.