High-Purity C60 Realizes 5.3% Efficiency of Organic Solar Cells
by Tetsuo Nozawa, Nikkei Electronics /Mar 28, 2008
Source: TechOn
http://techon.nikkeibp.co.jp/english/NEWS_EN/20080328/149683/
Osaka University and Osaka City Research Center announced the development of a new organic solid-state solar cell with a cell conversion efficiency of 5.3%. The announcement was made at the 55th Meeting of the Japan Society of Applied Physics, which is now taking place. The researchers reportedly succeeded in developing the solar cell with the use of extremely pure C60 crystals. The conversion efficiency of this cell is the highest in Japan for an organic solid-state solar cell (or an organic thin-film solar cell) with a p-i-n structure. It is also the second highest in the world, after Northwestern University’s record (5.2-5.6%) announced in February 2008.
The latest solar cell has a structure consisting of ITO (transparent electrode), H2Pc, i-layer, C60, NTCDA and Ag (electrode). H2Pc is phthalocyanine. NTCDA is naphthalenetetracarboxylic dianhydride.
The i-layer was obtained by simultaneously forming H2Pc (p-type semiconductor) and C60 (n-type semiconductor) by vapor-deposition. The layer has a complicated structure, referred to as “bulk hetero structure,” consisting of p- and n-type semiconductors. Recently, many organic solid-state solar cells employ this structure.
The major improvements in the latest cell are the materials of the semiconductor layers, especially, C60 with a purity of seven nines (99.99999% or higher) and the extremely thick (960nm) i-layer. With these two improvements alone, the cell conversion efficiency was improved from the existing 2.5 to 5.3%, which is among the highest in the world, according to the researchers.