Transparent White OLED‐Based Brain Stimulation With Invisible Flicker and Photobiological Safety Evaluation

ABSTRACT An invisible flickering, transparent white organic light‐emitting diode (TrWOLED) system has been developed as a safe, innovative wearable electroceutical for therapeutic 40 Hz brain stimulation. While conventional light visual stimulation often induces visual fatigue due to stroboscopic flickering, this platform utilizes an invisible flicker mechanism. By alternating red and blue chromatic stimuli at 40 Hz, it generates a steady white light perception, effectively eliminating flicker‐induced discomfort. The device features a monolithically integrated, vertically stacked architecture with a shared Ag intermediate electrode, enabling efficient 40 Hz modulation within a single transparent form factor. Experimental results demonstrate 60.1% transmittance at 550 nm (peak 69.9%), ensuring seamless daily integration. Safety assessments at a target 700 cd/m 2 luminance, an intensity optimized for maximum neural entrainment based on clinical efficacy, reveal a therapeutic illuminance of 1177 lx and a photobiological dose of 2.46 J/cm 2 per hour, well within human safety limits. Furthermore, the system exhibits exceptional thermal stability with fluctuations under 0.5°C, ensuring physiological safety for the ocular area. These findings validate the invisible flickering TrWOLED system as a robust solution for noninvasive brain entrainment, providing a practical path toward wearable photonic healthcare for cognitive management.