From the article it seems to be a coating on the LED light source. It seems having a graphene coating on the LED makes it last longer. I'm not sure how a graphene coating would make it shine any brighter (or have the same brightness with less power usage for that matter). Graphene is a very good conductor of electricity, but a coating doesn't conduct.
To be honest, given the physical properties of graphene and how tricky it currently is to make in bulk, this seems a pretty poor application of it to be honest.