Influence of interfacial roughness on slot-die coatings for scaling-up high-performance perovskite solar cells

Slot-die coating (SDC) technology is a potential approach to mass produce large-area, high-performance perovskite solar cells (PSCs) at low cost. However, when the interface in contact with the perovskite ink has low wettability, the SDC cannot form a uniform pinhole-free perovskite film, which reduces the performance of the PSC. To address this issue, in this study, the wettability of the hole transport layer (HTL) interface was investigated in depth by analyzing the variation of wettability with process and its correlation with the roughness of the HTL interface. As a result, it was found that SDC could increase the roughness of the HTL interface to improve wettability and form a uniform high-quality perovskite layer without pinholes, and furthermore, SDC-based NiOx/Me-4PACz HTL suppressed energy losses at the HTL/perovskite interface. In addition, a unit cell achieved 19.17% of efficiency with long-term stability and lab cell-sized modules showed up to 17.42%. Slot-die coating is promising for the large-scale and low-cost manufacture of perovskite solar cells. Here, the effect of wettability of the hole transport layer is investigated, finding that increased surface roughness improves wettability and prevents pinhole formation, favoring solar cell efficiency.