The overall efficiency is still at 8.6% rate of conversion (light to electricity) but it's a big jump from the 2.9% achieved earlier. In any case we must not forget that the source of this electricity (solar light) is gratis an abundant, so this rate of conversion is quite good, provided that we want to make use of it and not keep dragging our feet in the dirty methods of energy-generation based on petroleum/gas or (worse) uranium.
The researchers said that if graphene solar cells reach 10 percent power conversion efficiency they could be a contender in the market place, if production costs are kept low enough.
Or if we account for the horrible hidden costs of the dirty energies, which are deflected towards the environment, the public and a future that is more and more our present and past - if we begin taxing (or totally banning) dirty energies for all the damage they cause.
This advance is just one of a number that have happened in the last years only in the field of solar energy. I used to keep track of this better at my old non-specialized blog Leherensuge.
Source: Science Daily.