Ultrathin, Self-Powered, Heavy-Metal-Free Cu-In-Se Quantum Dot Photodetectors for Wearable Healthcare Monitoring System

Abstract

Mechanically deformable photodetectors (PDs), vital for wearable health monitoring systems using photoplethysmography (PPG), require high detectivity, fast response time, self-powered operation, and an ultrathin form factor for next-generation applications. We propose ultrathin self-powered PDs using heavy-metal-free CISe quantum dots (QDs) for high-performance wearable PPG systems. Despite a thin light-absorbing QD layer (~40 nm), PD shows excellent performance with a specific detectivity of 2.10 × 10¹² Jones and a spectral range of 250-1,050 nm at zero bias. This performance is due to the strategic use of materials and design: CISe QDs, MoS₂-nanosheet-blended PEDOT:PSS hole transport layer, ZnO nanoparticle electron transport layer, Ag and ITO electrodes, and ultrathin form factor (~120 nm excluding electrodes) ensuring excellent mechanical deformability. These features enable effective QD-PDs for wearable real-time PPG monitoring, expanding their potential in mobile bioelectronics.