Ligand-bridged charge extraction and enhanced quantum efficiency enable efficient n-i-p perovskite/silicon tandem solar cells

Translating the high power conversion efficiencies of single-junction perovskite solar cells in their classic, non-inverted (n-i-p) architecture to efficient monolithic n-i-p perovskite/silicon tandem solar cells with high current densities has been a persistent challenge due to the lack of low-temperature processable, chemically-insoluble contact materials with appropriate polarity and sufficient optical transparency. To address this, we developed sputtered amorphous niobium oxide (a-NbOx) with ligand-bridged C-60 as an efficient electron-selective contact, deposited on the textured-silicon bottom cell. For the sunward, hole-selective contact we implemented a stack of molecularly doped broadband transparent evaporated 2,2 ',7,7 '-tetra(N,N-di-p-tolyl)amino-9,9-spirobifluorene (spiro-TTB) and atomic layer deposited vanadium oxide, which further enhances the device quantum efficiency. Combining these contact materials with two-dimensional perovskite passivation on the micrometer-thick solution-processed perovskite top cell yields 27% efficient monolithic n-i-p perovskite/silicon tandem solar cells, which represents one of the highest power conversion efficiencies reported on pyramidal textured crystalline silicon bottom cells, and the highest with this polarity.

Automated summary

By developing new contact materials, the research team successfully converted high-efficiency single-junction perovskite solar cells into efficient perovskite/silicon tandem solar cells, achieving a conversion efficiency of up to 27%.