Shingling meets perovskite-silicon heterojunction tandem solar cells

The current work focuses on the question if shingling can be a suitable interconnection method for perovskite-silicon tandem (PVST) cells. Cell-to-module (CTM) analysis was conducted to investigate the effect of the number of the metallization fingers and cut size (1/4, 1/5, 1/6 and 1/7 of the original wafer) on the I–V characteristics of PVST shingle cells, defining an optimum number of fingers for each of the cut sizes. The simulation was based on M6 wafers with an edge length of 166 mm, showing that smaller cut size with more fingers exhibit lower current, but higher fill factor and efficiency. Furthermore, power gains and losses from cell to module depending on the shingle size were analyzed. The simulation was based on a module design with 10 strings in parallel and shingles of 1/4, 1/5 and 1/6 cut sizes. CTM analysis revealed that smaller shingle cut sizes result in higher module efficiencies due to their higher initial efficiency and optical gains from overlap. According to the performed simulations, assuming an initial cell efficiency of 25.0 % (1/6 cut with 95 fingers), a module efficiency of 23.4 % can be reached. In order to demonstrate the feasibility of shingle interconnection and full-format module integration of PVST cells, low-temperature silver metallization with a screen-printing approach was utilized on M6 precursors provided by Oxford PV. After metallization, cells were cut (166 mm × 33.2 mm) and interconnected into shingle strings with an automatic process. They were then integrated in glass-glass (GG) solar modules. The prototype modules exhibited no visual defects and demonstrated performance in line with the initial cell efficiency. The highest achieved module efficiency was 22.8 % based on the aperture area of 1.5 m2 and exhibited a power PMPP of 336.5 W. Throughout the whole prototype fabrication process, only commercially available materials and industrial manufacturing equipment was used. To conclude, shingling has been demonstrated as a viable interconnection approach for PVST cells. Simulation and prototype production confirmed the potential of shingle modules to achieve high efficiencies.