Google this, it's on Amazonsomething else to bear in mind - that light you are thinking of buying.. in the ebay ad i found, there is no mention of using it for horticulture and no breakdown of the specific colour ranges/frequencies which may be a bad sign.
Someone far more knowledgeable may offer some info though, just thought i'd offer a few thoughts.
EDIT: just saw you mentioned it is a panel and not a bulb- couldnt see it on ebay though - can you post a link?