Selective nano-emitter fabricated by silver assisted chemical etch-back for multicrystalline solar cells

Abstract

A nano-emitter is fabricated by one-step Ag-assisted chemical etch-back after conventional POCl₃ diffusion, with the intention of overcoming the relatively low efficiency of black silicon solar cells. The conversion efficiency of the multicrystalline silicon nano-emitter solar cell with a suitable sheet resistance is significantly improved thanks to the increased open-circuit voltage, short current and fill factor, all arising from the reduced surface recombination and Auger recombination, as well as the improved ohmic contact. In order to further improve the performance of the solar cell, it is combined with the selective emitter technique, resulting in a multicrystalline silicon selective nano-emitter solar cell. The selective emitters – etched back for different sheet resistances – are investigated to optimize the conversion efficiency. A 16.94% conversion efficiency is finally achieved with a sheet resistance of 107 Ω sq⁻¹, which is 0.34% higher than a standard selective emitter solar cell. Such an improved efficiency can be attributed to a lower reflectivity, a more homogeneous emitter, a smaller surface area and Auger recombination.