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Supporting Information
High efficient inverted bulk-heterojunction solar cells with a gradiently-doped ZnO
layer
Sungho Nho,1 Gyoelim Baek,1 Sujung Park,1 Bo Ram Lee,2 Myung Joo Cha,3 Dong Chan Lim,4 Jung Hwa Seo,3 Seung-Hwan Oh,5 Myoung Hoon Song,2 Shinuk Cho1*
1Department of Physics and EHSRC, University of Ulsan, Ulsan 680-749, Republic of Korea2School of Mechanical and Advanced Materials Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan , 689–798 , Republic of Korea3Department of Materials Physics, Dong-A University, Busan, 604-714, South Korea4Surface Technology Division, Korea Institute of Materials Science (KIMS), Changwon 641-010, Republic of Korea.5Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute (KAERI), Jeongeup 580-185, Republic of Korea.
*Corresponding Author; E-mail: [email protected]
Additional AFM images
Figure S1. AFM phase images (10 μm×10 μm) of (a) pristine ZnO ripple, (b) ZnO ripple covered with Li2CO3,
(c) ZnO ripple covered with K2CO3, (d) ZnO ripple covered with Na2CO3, (e) ZnO ripple covered with Cs2CO3,
and (f) ZnO ripple covered with (NH4)2CO3.
Electronic Supplementary Material (ESI) for Energy & Environmental Science.This journal is © The Royal Society of Chemistry 2015
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Figure S2. AFM height images (2 μm×2 μm) of (a) pristine ZnO ripple, (b) ZnO ripple covered with Li2CO3, (c)
ZnO ripple covered with K2CO3, (d) ZnO ripple covered with Na2CO3, (e) ZnO ripple covered with Cs2CO3, and
(f) ZnO ripple covered with (NH4)2CO3.
Figure S3. AFM phase images (2 μm×2 μm) of (a) pristine ZnO ripple, (b) ZnO ripple covered with Li2CO3, (c)
ZnO ripple covered with K2CO3, (d) ZnO ripple covered with Na2CO3, (e) ZnO ripple covered with Cs2CO3, and
(f) ZnO ripple covered with (NH4)2CO3.
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IPCE spectra
300 400 500 600 700 8000
102030405060708090
Reference Cesium carbonate Sodium carbonate Potassium carbonate Ammonium carbonate Lithium carbonate
IPCE
(%)
Wavelength (nm)Figure S4. IPCE spectra of inverted BHJ solar cells with doped ZnO layers.
200 300 400 500 600 700
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1-R
Wavelength (nm)
Reference Cesium carbonate Sodium carbonate Potasium carbonate Ammonium carbonate Lithium carbonate
Figure S5. 1-R spectra obtained from the solar cells with doped ZnO ripple layer using various alkali
metal carbonate salts. (ITO/ZnO ripple/active layer/MoO3/Ag)
In the IPCE spectra, the reference device and (NH4)2CO3 device show a peak at 450 nm, but other devices show a red-shift to 480 nm. This spectral shift is most likely due to the different interference between incident light, scattered light, and reflected light by back electrode. In the absorption profile obtained from reflectance measurement, the device with pristine ZnO ripple and ZnO ripple doped with (NH4)2CO3 shows a slightly different shape compared to the other devices with ZnO ripple doped with Li2CO3, K2CO3, Na2CO3, or Li2CO3. A similar shift was observed in the 1-R spectra.
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UPS spectra
15 10 5 0 4 3 2 1 0
Binding Energy (ev)
Inte
nsity
(a.u
.)
ITO
ZnO
K2CO3
Na2CO3
Cs2CO3
(NH4)2CO3
Li2CO3
Figure S6. UPS spectra of ZnO doped with various metal carbonate salts.
Absorption spectra
300 400 500 600 700 8000.0
0.2
0.4
0.6
0.8
1.0
320 360 4000.0
0.2
0.4
0.6
0.8
Abso
rban
ce (n
orm
alize
d)
Wavelength (nm)
ZnO ZnO+K2CO3
ZnO+Na2CO3
ZnO+Cs2CO3
ZnO+(NH4)2CO3
ZnO+Li2CO3
Abso
rban
ce (n
orm
alize
d)
Wavelength (nm)
Figure S7. Absorption spectra of ZnO ripple layers doped with various metal carbonate salts. The extracted
energy gap size of pristine ZnO and ZnO doped with K, Na, Cs, and Li was 3.32 eV. The energy gap of ZnO
doped with NH4 was 3.26 eV.
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Solar cells parameters distribution
Pristine w/ K w/ Na w/ Cs w/ NH4 w/ Li0.55
0.60
0.65
0.70
0.75
0.80
V oc (V
)
Dopant (M2CO3)Pristine w/ K w/ Na w/ Cs w/ NH4 w/ Li
14
15
16
17
18
19
J sc (m
A/cm
2 )Dopant (M2CO3)
Pristine w/ K w/ Na w/ Cs w/ NH4 w/ Li0.55
0.60
0.65
0.70
0.75
Fill
Fact
or
Dopant (M2CO3)Pristine w/ K w/ Na w/ Cs w/ NH4 w/ Li
4
6
8
10
PC
E (%
)
Dopant (M2CO3)
Figure S8. Voc, Jsc, FF, and PCE distributions for the solar cells with a doped ZnO ripple layer using various
alkali metal carbonate salts. The data were obtained from 30 devices for each case (total 180 devices).
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Active layer morphology
Figure S9. AFM height images of PTB7 and PC70BM BHJ composites deposited on (a) pristine ZnO ripple
layer, (b) ZnO ripple covered with Li2CO3, (c) ZnO ripple covered with K2CO3, (d) ZnO ripple covered with
Na2CO3, (e) ZnO ripple covered with Cs2CO3, (f) ZnO ripple covered with (NH4)2CO3.
Figure S10. AFM phase images of PTB7 and PC70BM BHJ composites deposited on (a) pristine ZnO ripple
layer, (b) ZnO ripple covered with Li2CO3, (c) ZnO ripple covered with K2CO3, (d) ZnO ripple covered with
Na2CO3, (e) ZnO ripple covered with Cs2CO3, (f) ZnO ripple covered with (NH4)2CO3.
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Thickness of metal carbonate layer and Sheet Resistance
The thickness of the alkali metal carbonate layer was measured with a confocal microscope (KeyenceVK-X200)
and the sheet resistance was measured using the Van der Pauw method.
Thickness a) (nm)
Sheet resistance (Ω/sq)
Pristine ZnO - 2.09 105
w/ Potassium 4.4 5.15 104
w/ Sodium 4.7 5.95 104
w/ Cesium 5.3 4.36 104
w/ Ammonium 8.1 9.81 104
w/ Lithium 6.2 3.01 104
a) (thickness of flat ZnO layer doped with metal carbonates)–(thickness of flat ZnO layer without doping).
Contact angle measurements
(e) (f)
(a) (b) (c)
(d)ZnO K Na
Cs NH4 Li
Figure S11. Contact angle measurement on ZnO ripple and doped ZnO ripple using various metal carbonate
salts.
The measured contact angle of the pristine ZnO surface was 39˚, while those of ZnO ripple doped with K2CO3,
Na2CO3, Cs2CO3, and Li2CO3 were 42˚, 46˚, 42˚, and 47˚, respectively. In the case of (NH4)2CO3, a slightly
lower contact angel of 36˚ was observed. However, such a change in contact angle is not sufficient to affect the
inner profile of the active layer.
