Environmental Engineering Reference
In-Depth Information
There are drastic effects of defects on PV solar cell reproducibil-
ity, yield, device performance, and stability. The reproducibility of
devices can be severely affected by the presence of several defect
levels,leadingtopinningatdifferentpositionsand,hence,producing
varying e
ciencies. The nature of measured I-V characteristics can
be affected by external forces such as applied electrical stresses,
light soaking, heating, or cooling. Because of the effects of a series
of defects, the shape of I-V curves can be changed after repeated
measurements due to the direction of data collection. It has been
found that peculiar kinks, sudden jumps, and various deformations
couldoccurinI-VcurveswhentheFermi-levelpositionmovesatthe
deviceinterface.Thesechangesoccurwhenthereisagroupofdefect
levelsandtheFermilevelisforcedtomoveacrosstheselevels.When
aseriesofdefectsispresentintheactivejunctionarea,improvement
of
V
oc
is observed with a corresponding reduction of
J
sc
values and
viceversa.TheFFandcurrentdensityvaluesaredrasticallyaffected
by the presence of active R&G centres. The above variations are
observed for devices with defects of considerable concentration.
The undesirable behaviours of solar cells based on inorganic
materials are mainly due to defects in the bulk materials, interfaces,
or the combination of both. In order to produce high-e
ciency,
stable, and long-life solar cells, defect identification, keeping the
benign defects, and the removal (or passivation) of detrimental
defects are essential. The establishment of these conditions for
solar cells based on different materials and structures will lead
to considerable improvement of PV solar cell performance in the
future.
References
1. I.M.Dharmadasa,N.B.Chaure,T.Delsol,A.P.Samantilleke,andJ.Young,
the six GB patents listed in the References section of chapter 2.
2. I. M. Dharmadasa, A. P. Samantilleke, J. Young, and N. B. Chaure (2002)
Semicond. Sci. Technol.
, 17, 1238.
3. I. M. Dharmadasa (2009)
Semicond. Sci. Technol.
, 24, 055016-055025.
4. I. M. Dharmadasa (2005)
Sol. Energy Mater. Sol. Cells
,
85
, 293.
