Embodiments of the disclosed subject matter provide a wearable device that includes an organic light emitting diode (OLED) light source to output light having one peak wavelength from a single OLED emissive layer, and a first barrier layer that is disposed over or between the single OLED emissive layer and one or more down-conversion layers. One or more regions of the single OLED emissive layer are independently switchable and controllable so that the wearable device is configurable to output a plurality of wavelengths of light. One of the plurality of wavelengths of light that is output is near infrared light.