World record solar cell with 44.7% efficiency
For those wondering about the significance of this announcement:<p>As several people have noted, what matters for solar PV isn't <i>efficiency</i> but <i>cost per Watt</i>.  The maximum <i>available</i> energy is 1W/meter^2 at ground.  Single-layer PV efficiency is on the order of about 40%.  Mutliple-layer cells can reach a maximum of around 80%.<p>Even with existing efficiencies, the land space necessary to dedicate to solar power for all electrical energy needs is reasonably small.  A percent or so of the Earth's surface.  The hard part will be fabricating the PV and/or CSP (concentrated solar thermal power) plants to collect that energy, estimates run well over $100 trillion globally (Jacobson & Delucchi).<p>A key limiting factor in solar, wind, and other intermittent renewables is <i>storage</i> (or baseload / standby power).  Assuming you'd want 7 days' total energy output on reserve, there's quite literally not enough lead in the world to build storage for just the US, let alone the rest of the world.  Pumped hydro storage is very efficient, but sites are limited.  Biomass similarly doesn't scale to present populations.  Geothermal is good for 5-20% of power demands depending on locations (and some places such as Iceland might be able to export energy).  Thorium reactors look like a plausible bet but require development.  Liquid metal / molten salt batteries (such as Donald Sadoway's designs) look like they're both cheap and abundant enough to make the grade, though they're still under development as well.<p>Solar power <i>does</i> have its equivalent of Moore's Law:  Swanson's Law.  Solar PV costs fall by 20% with each doubling of capacity.  It's held since the 1970s and looks likely to continue.  Effectively, costs half about every 3 years.
<a href="http://www.economist.com/blogs/graphicdetail/2012/12/daily-chart-19/print" rel="nofollow">http://www.economist.com/blogs/graphicdetail/2012/12/daily-c...</a><p>In short:  this is mostly of significance for applications in which space and/or weight are at a premium:  satellite or possibly solar-powered aircraft (ultralights or airships most likely).  For ground-based generation, look for costs to come down further.<p>And pray for highly effective storage solutions.