As per here: http://web.mit.edu/newsoffice/2008/solarcells-0710.html

In summary, some boffins over at MIT have found a way to concentrate light passing through windows to increase the efficiency of solar cells on the edges of said windows. This makes power generation on a large scale (such as office buildings) very feasible.

"the team believes that it could be implemented within three years--even added onto existing solar-panel systems to increase their efficiency by 50 percent for minimal additional cost. That, in turn, would substantially reduce the cost of solar electricity."

"the focused light increases the electrical power obtained from each solar cell "by a factor of over 40"

Looks pretty neat.

Its a neat idea, however the solar cells themselves are not any more
efficient. They just make more power due to the focused light, hence
greater light intensities.

Heres a pic showing the window. basically, they place solar cells at the edges where you see the bright colors.
The window separates the colors from the white light. White light is made up all the colors.
The solar cells are tuned to absorb that particular wavelength (color) better than the full spectrum of light.

The solar collectors, although aren't any more efficient, abosorb different wavelenghts better than others.
There is also less of them been used, hence providing us with lower $$$ per watt. Windows look great as well .