This is an extension that adds a button to gnome panel that when clicked
instantly turns off the monitor.
xset dpms force off is executed in
git clone https://bitbucket.org/xtranophilist/gnome-shell-extension-screen-off.git
mv gnome-shell-extension-screen-off/ screen-off@xtranophilist
Alt+F2 to open run command prompt
Screen Off Extension from Extensions from