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 × 1012 Jones without external bias and broadband CPL detection (gIph: ∼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 × 1012 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.