At a guess, being able to easily augment sunlight in parts of the world that get few hours of sunlight during local winter. Sun shines through when it's there,

At a guess, being able to easily augment sunlight in parts of the world that get few hours of sunlight during local winter. Sun shines through when it's there, LED takes over when not. However in practice I don't think this would be useful - they're considerably less efficient than existing LEDs (currently 1% vs 25-30%) and I think that efficiency is more of a problem than transparency.