Broadband Circularly Polarized Light Detection via Spin‐Selective Charge Transport in Quantum Dot Photodiodes

ABSTRACT Circularly polarized light (CPL) detection provides polarization‐resolved information, enabling advanced applications in quantum technologies, bioimaging, secure communications, and multi‐level optical data processing. However, conventional CPL photodetectors typically rely on intrinsically chiral absorbers, restricting operation to the UV–vis range and hindering extension into the near‐infrared (NIR) and shortwave infrared (SWIR), which are critical for deep tissue imaging and low‐visibility sensing. Here, we demonstrate broadband CPL detection with quantum dot (QD) photodiodes that exploit the chiral‐induced spin selectivity effect in chiral‐ZnO charge transport layers. Chiral ligand‐functionalized ZnO electron transport layers selectively transmit spin‐polarized charge carriers from QDs, enabling CPL‐specific photocurrent generation even in spectral regions without intrinsic chiral absorption. Heavy‐metal‐free Cu–In–Se QD‐photodiodes exhibit outstanding specific detectivity ( D ^* ) of 1.28 × 10 ¹² Jones without external bias and broadband CPL detection ( g _Iph : ∼0.17 at 260 nm and ∼0.13 at 780 nm), while PbS QD‐devices extend CPL detection across 250–1700 nm (UV–Vis–NIR–SWIR) with superior performance ( D ^* : 1.45 × 10 ¹² Jones). The chiral‐transport‐driven strategy offers fundamental insights into CPL photodetection and establishes a scalable and optically passive platform for broadband polarization‐resolved optoelectronics.