How to show WordPress Parent and child category different PAge?

I am currently trying to do a directory style site, and I currently have parent categories and child categories. Right now I have the parent categories showing and when you click on the parent it shows the child categories. Problem is now, I can't figure out how to display all the material in the child categories when you click on the child categories. Is there a conditional statement or a way that I can have the child categories go to the archive.php so it can display something else. Right now parent and the child categories pull from the category.php, so they end up being the same page.