Lead-free perovskite photo-responsive light-emitting diodes for monolithic heart pulse sensors

The development of miniaturized and mechanically flexible wearable optical health monitoring requires compact, biocompatible optoelectronic devices. Thin film devices based on perovskites, capable of both light emission and detection functionalities, offer a promising route toward such integrated systems. However, most reported dual-functional perovskite devices rely on toxic lead-based compositions, limiting their applications in skin-contact and wearable devices. Here, we demonstrate a lead-free tin-based perovskite dual-functional device, enabled by a synergistic dual-additive strategy to suppress defects and improve film crystallinity. The resulting device exhibits high-efficiency emission (radiance: 142 W m−2 sr−1, EQE: 7.56%) and sensitive photodetection (detectivity 1.53 × 1012 Jones). By integrating two perovskite diodes on a single flexible substrate, we realize a monolithic pulse sensor capable of real-time heart-rate monitoring. This work establishes a lead-free, flexible perovskite platform for bio-optoelectronic sensing, offering a promising pathway toward next-generation wearable healthcare systems.