Multifunctional Wearable OLED-OPD System with Wavelength-Tunable Emission for Phototheranostics

The growing demand for noninvasive wearable healthcare technologies calls for compact platforms capable of integrating diagnostic sensing and therapeutic light delivery within a single device. Conventional systems typically rely on spatially separated light sources or rigid inorganic LEDs, leading to inefficient area usage and limited mechanical compatibility with soft biological tissues. Here, we present a multifunctional wearable optoelectronic platform based on wavelength-tunable organic light-emitting diodes (WTOLEDs) integrated with organic photodiodes (OPDs). The vertically stacked red and blue OLED structure enables polarity-dependent wavelength switching under AC driving, generating alternating emissions at 624 nm and 464 nm from a single compact device without lateral source separation. The surrounding geometry, in which the light-emitting region encircles the light-receiving element, provides an area-efficient optical interface that enhances optical coupling and signal sensitivity within a flexible form factor. Using this platform, we demonstrate dual-wavelength physiological monitoring via photoplethysmography (PPG) and therapeutic applications, including red-light photobiomodulation and blue-light-mediated bilirubin photodegradation. The device further exhibited stable thermal and mechanical performance under wearable operating conditions. These results establish a compact phototheranostic architecture enabling wavelength-selective sensing and therapy within a single wearable platform.