Brightness or blackscreen command/feature

Hello Community,

I’m spending hours trying to find a solution. So I ask you for help.

What I need is a command to either toggle the brightness of kodi or force a blackscreen on my TV, but not turning it off.
The reason is, the audio of my kodi is trough my TV. So if I want to listen to a documentation or music my TV is to bright and the flickering from bright to dark and back makes it difficult to sleep. So I want to be able to toggle between normal brightness and nightmode, so I keep have the audio but (rarly) no picture.

Can someone please help me?