Pvi20 Front Cover indd

Current loss analysis 
The various current losses are quantified 
at the maximum power point by applying 
relatively simple mathematical formulae 
[1]. The losses due to metallization, front-
surface reflectance and front-surface 
escape (this is light that ‘escapes’ from the 
solar cell device without being absorbed 
– see Fig. 3) are calculated from the 
measurements and using the photon flux 
of the AM1.5G spectrum. The current 
losses due to shunt resistance and diode 
recombination are calculated from a 
one-diode model using the measured 
resistance at the maximum power point. 
The recombination losses in the solar cell 
are determined using the calculated IQE 
that is properly corrected for the non-ideal 
reflection by the front metal grid.
The resulting current losses for the 
investigated Al-BSF solar cell are shown 
in Fig. 4. It is clear from this that most of 
the current is lost by the non-perfect 
IQE of the solar cell, which explains 
the PV industry’s interest in solar cell 
designs featuring a selective emitter and 
a passivated rear. The current loss due to 
metal shading is also significant, which is 
why all-back-contact solar cells and metal-
wrap-through and emitter-wrap-through 
solar cells are attracting a lot of attention.
“
Most of the current is lost 
by the non-perfect IQE of the 
solar cell.
”
Figure 2. External and internal quantum efficiency and reflectance measurements of a standard industrial p-type Al-BSF silicon 
wafer solar cell: (a) full-area, and (b) active-area corrected.
(a)
(b)
400
600
800
1000
1200
0
20
40
60
80
100
EQ
E,
IQ
E,
R (
%
)
Wavelength (nm)
EQE
IQE
R
400
600
800
1000
1200
0
20
40
60
80
100
EQ
E
aa
, IQ
E
aa
, R
aa
(%
)
Wavelength (nm)
EQE
aa
IQE
aa
R
aa
Metal shading
100% loss
Acve area
Acve area
Front-surface 
escape
Front-surface
reectance