Brief note: 5.9 % power conversion efficiency (german, translation here; [Update 28.11.2009] it now says 6.07%) from small molecule p-i-n tandem solar cell with 2 sqcm area, made by Heliatek in Dresden. Nice picture (also by Heliatek:-)
The claim “new world record: efficiency of organic solar cell increased to 5.9%” should be preceded by “almost”, or succeeded by “based on small molecules”, because less than 2 months ago, Konarka had a press release about a certified efficiency of 6.4% for an organic bulk heterojunction solar cell. Although not mentioned in the press release, this one is probably not a tandem cell.
[Update 3.9.2009] After talking to Moritz Riede, a researcher from Dresden, I understood that the world record is unique in as far as the area is above one square-centimeter: 2 cm2, whereas the Konarka cell has only 0.76 cm2 – almost at, but not quite above “unity”. This distinction comes from the solar cell efficiency tables by Green et al. (see for instance [Green 2009]).
Thus, the 5.9% are best for small molecule based solar cells, and the best organic solar cells above one cm2: congratulations!