Highly Efficient, Spatially Pure Circularly Polarized Luminescence from Bilayer Self‐Assembled Colloidal Quantum Wells and Soft Helical Superstructures

Abstract Circularly polarized luminescence (CPL) is important for multiple photonic technologies. It can be achieved with high asymmetry factors ( g _lum ) by combining quantum emitters (QEs) with one‐dimensional helical superstructures (1D‐HS). However, existing 1D‐HS systems face challenges of maintaining polarization purity across viewing angles, primary due to the mismatch between QE emission profiles and the photonic bandgap of 1D‐HS across off‐normal directions. Herein, efficient and controllable CPL is proposed and developed using the self‐assembly of colloidal quantum wells (CQWs) coupled with cholesteric liquid crystals (CLCs). The face‐down CQWs assemblies with over 90% in‐plane transition dipole moments enables directional emission along the liquid crystal helical axis within the light escape cone. At the same time aligning their narrow emission spectra to the edge of the CLCs reflection band significantly enhances the spectral coupling. This results in highly efficient CPL with an improved g _lum of 1.47–1.82 (±0.03) over an expanded viewing range (±40°) and a large increase (53.3%) in extraction efficiency, supported by comprehensive angle‐resolved and wavelength‐resolved spectroscopy as well as optical simulations. Moreover, this approach facilitates the development of novel anti‐peeping and angle‐dependent luminescent devices. This work establishes a versatile platform for spatially homogeneous and tunable CPL in next‐generation photonic systems.