Light therapy is thought to affect brain chemicals linked to mood and sleep

light therapy which may help reduce some daytime sleepiness and certainly described to help mood. 

https://www.mayoclinic.org/tests-procedures/light-therapy/about/pac-20384604

Light therapy is most effective when you have the proper combination of light intensity, duration and timing. For most people, light therapy is most effective when it's done early in the morning, after you first wake up. Your doctor can help you determine the light therapy schedule that works best.