Complete Report - University of New South Wales

7.1 PROGRESS AGAINST CENTRE DESIGNATED MILESTONES
In its initial application, the Centre proposed 18 challenging research milestones for its
5-year program, as well as 4 teaching milestones, 4 “linkage” milestones and 5 governance
milestones. Progress towards these milestones is reported below.
Research Milestones
A.1
Efficiency improvement of standard p-type silicon cells to 26% or n-type cell to 24%.
With the growing industry interest in n-type wafers for solar cell manufacturing, the Centre
has focused on developing its highest performance solar cells to suit this type of wafer.
Excellent progress has been made, particularly in recent months, with the Centre equalling
the world record of 22.7% effi ciency for this type of wafer, held for more than a decade by
Stanford University.
Importantly, the Centre’s new high effi ciency designs for the n-type wafers are still far from
optimised with the expectation that the Centre will set more world records in this area during
the next couple of years, thereby establishing a clear lead over competitors internationally.
A.2
Efficiency improvement of Si cell boosted by an up- or down- converter to 28%.
This milestone is linked to A10. An increase in spectral response in the range 1480 to
1580nm (i.e. well below the band edge of Si) for a bifacial Si cell has beendemonstrated
representing a very small increase in current, which nonetheless represents a proof of
concept.
Further work on increasing the sensitivity to light between 1250 & 1480nm which should in
turn increase this up-conversion current, is being carried using two approaches (see Section
4.5.5). PbSe quantum dots absorb photons between 1250 & 1480nm, which then undergo
non-radiative transitions and are re-emitted at longer wavelengths, inside the absorption
range of the erbium (Er) in the Up-conversion phosphors. Alternatively, addition of dysprosium
(Dy) to the erbium.doped phosphors, provides energy levels for absorption of photons between
1250 & 1480nm. Again these decay non-radiatively in the Dy atoms to be re-emitted within
the Er absorption band.
A patent application has been fi led on a new up-conversion approach.
A.3
Demonstration of large-area buried contact silicon solar cell of efficiency above 21% and/or
multicrystalline buried contact solar cell above 18%.
The link between boron diffusion induced dislocations and a key recombination mechanism
limiting solar cell performance for p-type buried contact silicon solar cells has been
identifi ed.
The boron diffusion induced dislocation has been identifi ed as one of the major effi ciency
limitations of double-sided buried contact solar cells, which have now reached effi ciencies as
high as 18.6% on FZ(Boron) and 18.6% on Cz(Ga) despite this limitation.
The signifi cance of defects in n-type and p-type silicon wafers using side by side comparison of
similar n-type and p-type solar cells has been demonstrated.
We have achieved cell effi ciencies as high as 19.2% on textured FZ(Phosphorus), and
performance levels almost as high on Cz(Phosphorus) n-type wafers.
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