Set shortcut with i3 for brightness.
Install blight for AUR
git clone https://aur.archlinux.org/blight.git
cd blight
makepkg -si
The doc: https://github.com/RPigott/blight
Set the shortcut
cd ~/.config/i3
vim config
I added this on this file:
bindsym $mod+F5 exec blight set -5%
bindsym $mod+F6 exec blight set +5%
Now reload I3 with mod+shift+r
Decrease brightness: mod+F5
Increase brightness: mod+F6