It wasn't so long ago that photovoltaic solar panels were expensive, hard—and dirty!—to produce, inefficient sources of very expensive power.
In the last little while, however, a flurry of advances have improved on all of those problems. So many announcements have come out lately that I've delayed this post repeatedly due to the sheer quantity of new information. But that's not going to stop, so I'll post what I have now, and I may post again later.
For a super-quick summary of first-generation photovoltaic power, the panels were made of silicon using a process that involves toxic chemicals and high temperatures, were very fragile, expensive, and had a low efficiency and limited lifespan.
But now they're becoming cheap, tough, flexible, easy to make, and remarkably efficient and durable.
Starting with the biggest difference: the new ones are made from plastic, not silicon.
It turns out that contaminating silicon crystals with phosphorus and boron isn't the only way to get a material that has electrons floating around in it when light bumps them loose. There are quite a few polymers which not only work quite well as semiconductors, they can absorb light energy more efficiently, allowing them to be thinner and still capture the same amount of light.
Some of the polymers are also soluble in an appropriate solvent, making them liquid and allowing them to be printed with an inkjet printer, or one of any number of well-established ways of getting a thin layer of liquid stuff in a pattern of your choice on the surface of your choice.
There's a wide variety of polymers, and each one reacts to a slightly different piece of the light spectrum. Some of them are transparent to light at a frequency they don't use, leading to stacking the cells so more of the light's spectral range is used and thus the cells operate at ever higher efficiencies.
There's even a new battery technology using pulp mill waste to store the charge from a solar cell for use at night, which takes advantage of the systems trees use to chemically store energy their leaves gather during the day.
This story isn't finished yet. There are still many things to discover—a better transparent electrode, for example: a solar cell needs electrodes on both sides to transmit electricity, but at least one of those sides has to let light through to the photosensitive material to create that electricity in the first place. Still, there are students making photovoltaics from fruit in a university chemistry class. The ease of production is coming into play, although perhaps not as easy yet as the press releases reprinted by the news media would have you believe: recent news about "paint-on solar panels" that can be applied as your house's next coat of paint may be simpler to create than past solar panels, but as of December 2011 when those stories started appearing, the "paint" needed to be annealed onto a conducting surface at 200C and they could only do small surfaces. Not quite as simple as repainting any old house.