Horizontally oriented compact colloidal quantum well films enable efficient and stable electroluminescent diodes

Colloidal quantum well-based light-emitting diodes are highly promising for electroluminescent applications owing to their high fraction of horizontally aligned transition dipole moments, but scalable fabricating their films with dominant horizontal dipole orientation for electroluminescent devices remain major challenges. Here, we utilize a two-phase driving flat arrangement strategy combined with Langmuir-Schaefer technology to create compact colloidal quantum well films with predominantly horizontal dipole alignment. The interfacial driving force between the two liquid phases facilitates the formation of uniform, densely packed films, which exhibit 90% horizontal dipole alignment, yielding a light extraction efficiency of 35.8%. The resulting devices achieve (4 mm²) an external quantum efficiency of 25.5%, a maximum luminance of 59,620 cd m^-2, and outstanding operational stability (T₉₅@100 cd m^-2 > 16,233 h). Moreover, this technique enables scalable fabrication of uniform colloidal quantum well films (100 cm²), maintaining luminance above 60,000 cd m^-2 in 4 cm² devices, indicating industrial feasibility.