Bioinspired Face‐Down Oriented Assembly of Ligand‐Engineered Colloidal Quantum Wells for Sensitive Polarimetric Photodetectors

ABSTRACT Chameleons achieve vivid and dynamic color changes through iridophore layers containing oriented guanine nanocrystals, whose controlled orienting and spacing govern reflection, polarization, and optical anisotropy. Inspired by this natural strategy, we translate the principle of orientational order into solution‐processed optoelectronics by assembling colloidal quantum wells (CQWs) into face‐down monolayers. Gas‐liquid interfacial self‐assembly drives CQWs to align their basal planes parallel to the interface, coherently orienting their intrinsically in‐plane dipoles across macroscopic films. Chloride ligand exchange further modulates interparticle spacing and reorients surface dipoles, thereby leading to type‐II band alignment at the CQWs/ReSe 2 heterojunction, which facilitates enhanced charge separation. The resulting photodetectors achieve a polarization ratio of 40.81, which is more than 20‐fold higher than that of pristine ReSe 2 detectors, along with a response time of 420 µs and a specific detectivity exceeding 10 11 Jones. Beyond quantitative metrics, the devices enable high‐contrast polarization‐resolved imaging and quaternary polarization‐encoded optical communication, faithfully reproducing input signals. By coupling the intrinsic anisotropy of CQWs with bioinspired orientation control, this work demonstrates how nanoscale units can be transformed into hierarchically oriented architectures that replicate and extend nature's polarization strategies, establishing a general design pathway toward solution‐processable, intelligent polarimetric optoelectronics.