I have an outside light that gives a little light at night but they do not like when I shine a flashlight in there to check on them sometimes lol. So I would say you wouldn't need one. When i put mine outside they were older (so many delays getting the coop and run built) so I never locked them...
Honestly when I put mine out there I just let them do what they wanted and they figured out where to sleep on night #2. And it seems they've already been exposed to the coop so it's not totally new to them. Mine do not free range in the yard (yet) but have access to their run 24/7 but I've...