Tandem Cells, Portable Power, Concentrators, Solar Trackers, Internal Refelecters, Back Contact etc. are all concepts of past. While the solar panels continue to spread and cover the rooftops, radio towers and land there are others working on raising the bar even further. "A single kilometer-wide band of geosynchronous Earth orbit experiences enough solar flux in one year to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today." Sounds like a quote from a scifi novel but may soon be a reality in near future.
Below is an article from CNN that talks about an interesting concept which may very well come true one day.
Cnn.com - How to harvest solar power?