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

Tin (IV) oxide (SnO₂) electron transport layer (ETL) emerges as the most promising n-type semiconductor material for flexible perovskite solar cells (f-PSCs). The (110) facet-dominated SnO₂ 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 SnO₂ 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 SnO₂ (101) and (200) facets. Accordingly, the champion f-PSCs on high-oriented SnO₂-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 cm². 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.