(b)
8.10
(a)
(b)
(c)
(d)
8.11
(a)
(b)
the potential barrier for electrons in the conduction band.
Calculate the depletion-region width at 0 V bias and at a bias of V a = 0.25 V.
Consider an n-p junction solar cell with external parameters J s c, V oc , and FF. The thickness of the n-type region
is much lower than that of the p-type region. This solar cell is uniformly illuminated with generation rate, G 0 ,
leading to an excess carrier concentration of δn and δp.
Show that in open circuit condition the open circuit voltage is equal to:
The bandgap voltage offset W is a useful parameter to study the solar cell quality. Basically W is a
measure of how close electron and hole quasi-Fermi levels are to the conduction and valence band
edges, respectively. It is defined as:
Show that W can be expressed as:
The performance of solar cells under concentrated light (irradiance larger than 1 sun) is generally better
in reference to standard test conditions. How is this reflected in Eqs. (8.57) and Eqs. (8.58)?
Calculate the W and ratio W/E gap of the various solar cells shown in Table 8.1. Which technologies
have, in absolute and relative terms, the largest fraction of band-gap energy available at the solar cell
terminals?
Table 8.1: Bandgap and open circuit voltage of single junction solar cells based on various semiconductor materials.
Technology
E G [eV]
V oc [mV]
W [eV]
W/E G
Ge
0.67
194
CIGS
1.1
689
c-Si (heterojunction)
1.12
729
GaAs
1.42
1000
CdTe
1.45
845
a-Si:H
1.76
950
AlGaInP
2.10
1560
An N-p heterojunction with doping concentrations N dN = 2 × 10 17 cm −3 and N ap = 6 × 10 17 cm −3 , consists of
the semiconductor materials listed in Table 8.2.
Draw the band diagram for this junction.
How much does the spike in the conduction band extend above the conduction band of the quasi-neutral
p-type region?
Table 8.2
Al 0.4 Ga 0.6 As
GaAs
8.10
(a)
(b)
(c)
(d)
8.11
(a)
(b)
the potential barrier for electrons in the conduction band.
Calculate the depletion-region width at 0 V bias and at a bias of V a = 0.25 V.
Consider an n-p junction solar cell with external parameters J s c, V oc , and FF. The thickness of the n-type region
is much lower than that of the p-type region. This solar cell is uniformly illuminated with generation rate, G 0 ,
leading to an excess carrier concentration of δn and δp.
Show that in open circuit condition the open circuit voltage is equal to:
The bandgap voltage offset W is a useful parameter to study the solar cell quality. Basically W is a
measure of how close electron and hole quasi-Fermi levels are to the conduction and valence band
edges, respectively. It is defined as:
Show that W can be expressed as:
The performance of solar cells under concentrated light (irradiance larger than 1 sun) is generally better
in reference to standard test conditions. How is this reflected in Eqs. (8.57) and Eqs. (8.58)?
Calculate the W and ratio W/E gap of the various solar cells shown in Table 8.1. Which technologies
have, in absolute and relative terms, the largest fraction of band-gap energy available at the solar cell
terminals?
Table 8.1: Bandgap and open circuit voltage of single junction solar cells based on various semiconductor materials.
Technology
E G [eV]
V oc [mV]
W [eV]
W/E G
Ge
0.67
194
CIGS
1.1
689
c-Si (heterojunction)
1.12
729
GaAs
1.42
1000
CdTe
1.45
845
a-Si:H
1.76
950
AlGaInP
2.10
1560
An N-p heterojunction with doping concentrations N dN = 2 × 10 17 cm −3 and N ap = 6 × 10 17 cm −3 , consists of
the semiconductor materials listed in Table 8.2.
Draw the band diagram for this junction.
How much does the spike in the conduction band extend above the conduction band of the quasi-neutral
p-type region?
Table 8.2
Al 0.4 Ga 0.6 As
GaAs