Circularly polarized electroluminescence from light-emitting diodes: mechanism, materials, and applications

Abstract

Circularly polarized luminescence (CPL) has gained significant interest in applications ranging from quantum computing and optical communications to data encryption and bioimaging. Light-emitting diodes (LEDs) that directly emit CPL offer clear advantages over chiroptical approaches, which rely on external optical elements to impart handedness to otherwise unpolarized light. In this review, we first outline the working principles of the two leading CPL-emitting LED architectures: CPLEDs, which do not require spin injection, and spin-LEDs, which rely on spin injection. We then summarize recent material advances—from organic and inorganic semiconductors to hybrid systems—that enable high-performance CPLEDs, alongside the latest developments in spin-LEDs. We analyse the dissymmetry factors of these device systems and discuss strategies to enhance both dissymmetry and overall device efficiency. By uniting advances in material design and device architecture, the field is poised to deliver high-performance CPL sources for nextgeneration photonic and spintronic applications.