Well! Light is a energy and energy can be stored. But light is an electromagnetic radiation and radiations cannot be stored. Light differs from others. Many physical concepts doesn't apply on it. And thus we don't know how to store it. Storing light can be very helpful. It can be used as a space fuel and may have many other uses. As a simple example think of opening a light source in an isolated dark room for some time and close the source as well as the doors of the room. When you will enter the room after some time the room would be dark again. The light being radiation are absorbed by the things in the room, even the walls. We know light is reflected by these matters and that's why we are able to see these objects but only a part is reflected and other part is absorbed. Hence after a few time all the light is absorbed and the intensity of the light becomes very low and finally it is completely absorbed.radiations are absorbed by every element we know.
But, if we are able to make a body which absorbs ~0 light (radiations) we might be able to store it. Hence the first step is to find or make an element that does not absorbs radiation. Then we can think of using it in various places.