With Technology the solar cell's limits with todays latest advancements are the size of coverage for the power produced.

My idea is to layer the solar cells one on top of the next, separated by very thin transparent material such as a high quality plastic or plexiglass such that the bottom of the solar cell material is covered in a highly reflective material as well as the sides of the plexiglass all towards the inside.

A series or band of light pipes are then molded into the sides of the layered cell structure such that the top edge takes in light from all 4 sides and transmits the light down to the next layer.

Once that light goes down to each layer below, it hits a reflector passing it into the area below each solar cell thereby reflecting the light over the solar cell below which will then give efficiency to the Nth power depending on how many layers you can put in, if you only use the layers of the solar cell material stacked onto the thinnest possible layer of plexiglass or other material to get the most output in the same square foot area as todays heavy solar cell that has such a heavy weight with its standard backing.