TECHNOLOGY
Stacking sidesteps the strain
in multi-junction cells
If terrestrial concentrator photovoltaics are to enjoy significant commercial success then
Issue I 2010
electricity generation costs must fall. One way to do this is to improve the design of the
cell with a stacked architecture that eliminates strain and current matching issues,
according to IMEC’s Giovanni Flamand.
-pv-management.com
.solar
Today the dominant multi-junction solar cell
www
T
he solar industry is changing. Although
silicon is still the dominant material for technology is the monolithic triple-junction
solar cell manufacture, alternative technologies like (InGaP/(In)GaAs/Ge) solar cell that was originally
20
thin-film and concentrator photovoltaics (CPV) are developed and commercialized for space
emerging. The latter of these promises to excel in applications. These devices feature In0.5Ga0.5P,
sunnier climes and involves the focusing of In0.01Ga0.99As and germanium cells that are
incident sunlight onto cells with a typical area of lattice-matched to a germanium substrate to
just 10-100 mm
2
. By focusing the light by a factor ensure excellent material quality and photovoltaic
of several hundred, it is possible to minimize the performance.
total expenditure on these relatively expensive
cells, and ultimately realize an acceptable cost-per- The conversion efficiency record for a multi-
Watt at the system level. junction cell under concentrated irradiation has
been broken on several occasions over the last
Generating costs for Concentrator Photovoltaic few years. Spectrolab has made the most recent
systems are also influenced by the efficiency of the claim for the record, and in August 2009 it
cell. Single-junction solar cells are inappropriate, announced an efficiency of 41.6 percent, which
because they are limited to a theoretical maximum was achieved under a concentration of 364 suns.
efficiency of about 30 percent, due to But this record may not last for long because
thermalization and transmission losses. In further improvements in monolithic multi-junction
comparison, multi-junction cells can produce far cells are expected. These could
higher efficiencies, because they cut thermalization come through either adding
losses by using several cells to absorb different more junctions to the
parts of the solar spectrum. stack, or using lattice-
mismatched solar
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61