Angular and Spectral Engineering of Red Organic Light-Emitting Diodes via Cavity-Induced Emission for Photobiomodulation-Related Cellular Responses.

Photobiomodulation using red and near-infrared light has emerged as a promising strategy for promoting skin regeneration because of its ability to stimulate mitochondrial activity and enhance cellular proliferation. However, the optical characteristics of the light source, including angular emission and spectral bandwidth, remain underexplored in terms of their influence on biological outcomes. Here, we demonstrate that emission-engineered red organic light-emitting diodes (OLEDs) can directly regulate cellular responses by tailoring both angular distribution and spectral properties. Flexible OLED devices were fabricated with three representative configurations: an indium tin oxide (ITO)-based Lambertian emission device (inflexible), a candle-emission device with a narrow spectral profile centered at 610 nm, and a batwing-emission device exhibiting angularly broadened and spectrally enriched output (610-650 nm). Systematic optical characterization revealed distinct differences in efficiency, full width at half maximum (FWHM), and angular emission patterns across these devices. Subsequent in vitro assays showed that both candle and batwing devices enhanced proliferation-related cellular responses relative to sham-irradiation and ITO controls, with the batwing device producing the strongest effect. The superior biological efficacy of the batwing device is attributed to its broadened multiwavelength emission, providing broader spectral overlap with biologically relevant wavelengths. The implications of these optical characteristics for tissue photobiomodulation are discussed based on previous studies. This work establishes a direct connection between OLED emission characteristics and biological efficacy, underscoring emission control as a key parameter in optimizing photobiomodulation.