This work shows a bimolecular additive engineering approach to prepare highly efficient wide-band-gap perovskite solar cells. The coupling of PEA + and SCN À provides a synergistic effect that overcomes growth challenges with either additive individually and improves perovskite quality with enhanced crystallinity, reduced defect density, and improved carrier mobility and lifetime. When coupling a semitransparent wide-band-gap perovskite top cell with a low-band-gap CIGS bottom cell, we achieve a 25.9%-efficient polycrystalline perovskite/CIGS 4-terminal thinfilm tandem solar cell.

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The fundamentals of using cracked film lithography (CFL) to fabricate metal grids for transparent contacts in solar cells were studied. The underlying physics of drying-induced cracks were well-predicted by an empirical correlation relating crack spacing to capillary pressure. CFL is primarily controlled by varying the crack template thickness, which establishes a three-way tradeoff between the areal density of cracks, crack width, and spacing between cracks, which in turn determine final grid transmittance, grid sheet resistance, and the semiconductor resistance for a given solar cell. Since CFL uses a lift-off process, an additional constraint is that the metal thickness must be less than 1/3 of the crack template thickness. The transmittance/grid sheet resistance/wire spacing tradeoffs measured in this work were used to calculate solar cell performance: CFL-patterned grids should outperform screen-printed grids for narrow cells (0.5−2 cm wide) and/or cells with high semiconductor sheet resistance (≥100 Ω/sq), making CFL attractive for monolithically integrated thin-film photovoltaic modules.

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