High‐Oriented SnO ₂ Nanocrystals for Air‐Processed Flexible Perovskite Solar Cells with an Efficiency of 23.87%

Abstract Tin (IV) oxide (SnO ₂ ) electron transport layer (ETL) emerges as the most promising n‐type semiconductor material for flexible perovskite solar cells (f‐PSCs). The (110) facet‐dominated SnO ₂ colloids are readily created, whereas other best‐performing (101) and (200) facets‐dominated ones with superior potential in interface modulation and lattice matching remain insufficiently explored. Here water‐soluble acryloyloxyethyltrimethyl ammonium chloride‐acrylamine (DAC‐AA) doping into SnO ₂ colloids produces more (101)‐ and (200)‐oriented crystal domains through lowering surface absorption energy and offering additional thermodynamic driving force. Theoretical and experimental analyses corroborate that the grain preference orientation induced by DAC‐AA modification strengthens heating transfer rate on the flexible substrate and favors lattice matching of perovskite (100) plane on SnO ₂ (101) and (200) facets. Accordingly, the champion f‐PSCs on high‐oriented SnO ₂ ‐DAC‐AA ETLs fabricated fully in ambient air conditions achieve the efficiencies of 23.87% and 22.41% with aperture areas of 0.092 and 1 cm ² . In parallel, the propitious interfacial lattice arrangement attenuates the formation of micro‐strain inside perovskite films, maintaining 92.5% of their initial performance after 10 000 bending cycles with a curvature radius of 6 mm.