Transcript Document

Basic research in fabrication CIGS solar cells
Hao Xu, Fang Lu
Department of Physics, Fudan University, Shanghai 200433, China
CuIn0.7Ga0.3Se2 (CIGS) based solar cell is one of the most
promising thin films solar cells. Its advantages include less
amount materials, light mass, high radiation hardness and
highest conversion efficiency in single-junction solar cell.
1 RF Magnetron Sputtering
(AZO buffer layer)
Only strong (002) peak is observed
in XRD, which indicates a
hexagonal wurtzite structure.
XPS show stoichiometric and nonstoichiometric atomic ratio of O/Zn
in different deposition distances.
Structure
•Grid Al
•ZnO:Al(200~400nm)
•i-ZnO(80~100nm)
•CdS(50nm)
•CuIn0.7Ga0.3Se2(1~2μm)
•Mo(0.5~1μm)
•Sola-lime glass (SLG)
100000
Zn 2p3/2 Count
O1s Count
40000
528
530
0
532
534
536
250000
200000
150000
100000
1018
538
-1 -1
60
40
4.5cm
6cm
7cm
20
0
200
Distance (cm)
300
400
500
600
700
800
75
0
1E19
1E20

1E21
-3
3.4
3.6
Photon Energy (eV)
3.8
I  I 0e
t
  h  Eg
2
2 Chemical bath deposition (CdS buffer layer)
Homogeneous process
Cd(CH3COO)2→Cd2++2CH3COOCS(NH2)2+OH-→SH-+CH2N2+H2O
SH-+OH- →S2-+H2O
Cd2++S2- →CdS↓
Heterogeneous process
NH4++OH-↔NH3+H2O
Cd2++4NH3 ↔Cd(NH3)42+
Advantages of CBD
1. Complete coverage of
the rough absorber surface
2. Remove natural oxide
from film surface
3. Passivate CIGS surface
to prevent surface
inversion
4. Protect CIGS from
subsequent ZnO sputtering
AZO(1%)
SAZO(1%,1%)
AZO(2%)
SAZO(2%,0.5%)
-4
10
0
10
1
10
2
10
3 Laser surface
anealing and C-V
 max   min
1

1  (n / nref 1 )1 1  (nref 2 / n) 2
eL
2m * kT
. exp(
e 2 Qt2
)
8 0 NkT
Plot of 1/C2 vs. V, yielding
NA =2×1015 cm-3 and buildin field VD=0.894V.

1
M
1

S
Resistivity stability of window
layer can be improved by
doping Si impurity
3500
3000
2500
2000
1500
1000
500
0
0
The roughness in absorber
lead to short circuit of solar
cell. A beam of unfocused
laser was introduced to melt
and smooth surface.
1
2VD
2V


C 2 A2 r  0 qNA A2 r  0 qNA
Small, compact CdS grain (50~100nm)
3
10
Exposure Time (h)
Surface Roughness (nm)
3.2
Burstein-Moss shift of
the absorption edge
1

-3
10
1000
2000
3000
4000
Distance (m)
Capacitance (pF)
0.00E+000
3.0
4.5cm
6cm
7cm
1028
Combined model in AZO films
Resistivity  (cm)

-2
 (cm )
5.00E+009
1026
 S   0 . exp( Eb / kT )
Concentration (cm )
High conductivity and optical
transmittance in visible region, nontoxicity, low cost, material abundance,
relatively low deposition temperature,
and high stability.
1024
Grain boundary scattering limited
transport model of Seto
25
900
1022
Binding energy (eV)
 M   min 
50
Wavelength (nm)
1.00E+010
1020
Semi-empirical model in ZnO
single crystal presented by
Masetti
0.5mcm
1.0mcm
80
2
10
100
20
1.50E+010
70
50000
100 (a)
Mobility (cm V s )
-1 -1
-3
20
2
Mobility (cm V s )
Transmittance (%T)
Resistivity (.cm)
30
7
(b)
60
(b)
Binding energy (eV)
10
2.00E+010
50
0
-3
6
60000
526
10
5
350000
0
21
-4
Dst=7cm
40
2(deg)
20000
10
10
Dst=6cm
300000
Concentration (cm )
10
Dst=4.5cm
30
(a)
80000
Resistivity
Concentration
Mobility
-2
(a)
Relative Intensity
Introduction
50
300K
40
270K
200K
30
-0.6
-0.4
-0.2
Reversed Bias (V)
0.0