Hmmm. Is 12% far higher than the Ovonic photovoltaic cells at a stabilized 10%?. I think other things, like cost and a proven high volume manufacturing technique are more important than that efficiency difference.
For more information, here is what the was said about this type of thin-film photovoltaic cell in the 30 July issue of Science:
Photovoltaic Technology: The Case for Thin-Film Solar Cells
A. Shah, 1 P. Torres, 1* R. Tscharner, 1 N. Wyrsch, 1 H. Keppner 2
(Only the one pertinent section is copied below)
"Copper indium diselenide and related materials.
Copper indium diselenide (CIS) and copper indium gallium diselenide (CIGS) are direct-gap
polycrystalline semiconductors with very high optical absorption coefficients and are presently being widely studied for application in solar cells, with the
corresponding module technology just reaching the stage of pilot production. CIS and CIGS are p-type semiconductors and are always used in a
heterojunction structure, mostly with very thin n-type cadmium sulfide (CdS) layers.
The efficiency record obtained to date for a small-size (0.449 cm2) laboratory cell is 18.8% (44), which is impressively high for a thin-film (3 æm absorber
thickness) polycrystalline solar cell. This is achieved with an effective bandgap of 1.1 to 1.2 eV for the absorber material: By partially substituting gallium for
indium in CuInSe2, the bandgap of this semiconductor can be increased, and the PV performance is optimized by increasing Voc. A further degree of
freedom is obtained by the partial substitution of S2 for Se2 (45). Other materials-oriented research efforts are directed at replacing the CdS window layer
with a cadmium-free material, such as In(OH, S) (46). At present, the efficiencies of CIGS modules (30 cm by 30 cm) with integrated series connection, as
fabricated in pilot production lines, are between 9 and 12% (47); this value is substantially lower than the laboratory record.
In terms of stability, CIS and CIGS solar cells do not have a problem of light-induced degradation; they generally show a slight increase in Voc and in
efficiency during the first hours of operation and can be remarkably stable, as was proven for periods up to 8 years (48). However, they do have a
problem of instability in a hot and humid environment (49).
It is expected that CIS and CIGS cells should be substantially cheaper than wafer-based crystalline silicon modules (once production can be mastered on a
large scale). However, if and when CIS and CIGS solar cell technology reaches a production volume on the scale of a few 100 MWp/year, the availability
and the price of indium will become a major issue: The availability of indium in Earth's crust is comparable to that of silver, and because of this relative
scarcity, indium has been subject to erratic fluctuations in world market price. For example, a sharp price increase was registered around 1980, when
Japanese liquid crystal display manufacturers started using large quantities of this material in their displays (4)." |
