Design And Optimization Of The Optical Structure For Perovskite/c-Si Tandem Solar Cells

Perovskite/c-Si tandem solar cells (TSCs) have become a promising candidate in recent years for achieving efficiency over 30%.Although general analysis has shown very high upper limits for such TSCs,it remains largely unclear what specific optical structures could best approach these limits.Here we propose the combination of perovskite/c-Si tandem structure with inverted nanopyramid morphology as a practical way of achieving efficiency above 31% based on realistic solar cell parameters.By full-field simulation,we have shown that an ultra-low surface reflectance can be achieved by tuning the pyramid geometry within the range of experimental feasibility.More importantly,we have demonstrated that the index-guided modes can be excited within the top cell layer by introducing a TCO interlayer that prevents coupling of guided light energy into the bottom cell.This light trapping scheme has shown superior performance over the Bragg stack intermediate reflector utilized in previous micropyramid-based TSCs.Finally,by controlling the coupling between the top and bottom cell through the thickness of the interlayer,current generation within the tandem can be optimized for both two-and four-terminal configurations,yielding efficiencies of 31.9% and 32.0%,respectively.These results have provided useful guidelines for the fabrication of perovskite/c-Si TSCs.