Supplementary material
Sheaf-Like-ZnO@Ag Nanocomposite Materials Modified Photoanode for
Low-Cost Metal-Free Organic Dye-Sensitized Solid-State Solar Cells
A. Pandikumar, K. M. Saranya and R. Ramaraj*
Centre for Photoelectrochemistry, School of Chemistry, Madurai Kamaraj University,
Madurai - 625 021, India.
Experimenatal details:
Synthesis ZnO NRs:
ZnO NRs were synthesized according to the reported procedure.1 Breifly, 1:4 molar
ratio of Zinc acetate and hydrazine hydrate were mixed in water under stirring untill a slurrylike precipitate formed. The stirring was continued for another 15 min and then the mixture was
subjected to microwave irradiation at 150 W for 10 min. The slurry became clear and a white
precipitate was obatined. The ZnO NRs precipitate was gathered by centrifugation (10000 rpm
for 10 min), washed repeatedly with absolute ethanol and distilled water and then dried in hot
air oven at 60 oC for 4 h.
Synthesis of sheaf-like-(ZnO@Ag)NCM:
The sheaf-like-(ZnO@Ag)NCM was prepared as follows. Typically 1 g of preformed ZnO
NRs was dispersed in 50 mL of double distilled water and 2.5 % (Wt) AgNO3 was mixed under
stirring. Then the pH of the reaction mixture was adjusted to 7 by using NaOH. The reaction
mixture was vigorously stirred for 2 h at 80 oC. The sheaf-like-(ZnO@Ag)NCM were gathered by
centrifugation (at 10,000 rpm for 20 min) and washed with 100 mL of double distilled water under
stirring for 10 min at 50 oC. The synthesized sheaf-like-(ZnO@Ag)NCM was dried under air hot
oven at 100 oC for 2 h in order to remove moisture completely.
2
Characterization studies:
Diffused reflectance spectra of ZnO NRs, sheaf-like-(ZnO@Ag)NCM, ZnO NRs-eosin-Y,
sheaf -like-(ZnO@Ag)NCM-eosin-Y thin films and absorption spectrum of eosin-Y using Shimadzu
UV-2550 UV–vis spectrophotometer fitted with ISR-2200 DRS accessory. Photoluminescence
spectra were recorded using a JASCO-FP-6500 spectrofluorimeter. SEM images and EDAX were
recorded using HITACHI (Model S–3400) scanning electron microscopy fitted with EDAX
accessories. X–ray diffraction (XRD) pattern were recorded on a Bruker AXS D8 Advance with Cu
Kα radiation (λ = 1.54178 Å). Oriel class-A solar simulator (91195A, Newport) with ozone free
450 W xenon lamp was used as a light source. A computer-controlled Autolab PGSTAT302N
electrochemical workstation was employed for current-voltage (J-V) measurements
Fabrication of DSSC:
The ZnO NRs and sheaf-like-(ZnO@Ag)NCM films coated on fluorine-doped tin oxide
(FTO) conducting glass were prepared according to the reported procedure.2 The ZnO NRs or
sheaf-like-(ZnO@Ag)NCM (1 g) were ground in a porcelain mortar with 0.7 mL of water
containing 67 µL of acetylacetone till the formation of a viscous paste followed by slow
addition of 2.7 mL of water and 30 µL of Triton X-100 under continuous grinding. Uisng this
colloidal mixture, the photoanode (1 cm2) was prepared on a FTO conducting glass using
doctor-blade technique. The film was dried and then sintered at 450 oC in a muffle furnace for
30 min and allowed to cool naturally upto 80 oC. The dye adsorption on the modified photoanode
was carried out by soaking the hot film (80 °C) in a ethanolic solution of eosin-Y or N719 and
keeping overnight at room temperature. The dye adsorbed photoanode was withdrawn from the
solution under a stream of nitrogen and was immediately wetted with PEO/TiO2/KI/I2 electrolyte.3
A platinized FTO counter electrode was then placed on it to have sandwiched solid–state DSSCs
after the solvent completely evaporated
3
Results and discussion:
Photocurrent-time (I-T) studies of DSSC:
The stability of the DSSCs and reproducibility of photocurrent production of the ZnO
NRs and sheaf-like-(ZnO@Ag)NCM based DSSCs sensitized with eosin Y (Figure S3) and N719
dye (Figure S4) were studied and the results are shown in Figures S3 and S4. Variations in the
photocurrent values can be attributed to the differences in the morphology of the modified
photoanode materials. The sheaf-like-(ZnO@Ag)NCM modified photoanode exhibits about ~2fold higher steady-state photocurrent than the ZnO NRs electrode. In the sheaf-like(ZnO@Ag)NCM modified photoanode based solid-state DSSC, as soon as the light was turned
‘on’, the photocurrent rises quickly to a maximum value and showed steady state current as
well. When the light was turned ‘off’, sudden fall in the photocurrent appears and there is no
current in the dark. The steady-state photocurrent-maximum remained the same after several ‘onoff’ cycles revealing the good stability of the DSSC.
Reference
1
D.K. Bhat. Nanoscale Res. Lett. 3, 31 (2008).
2
S. Suresh, A. Pandikumar, S. Murugesan, R. Ramaraj, and Samuel Paul Raj, Sol. Energy 85,1787
(2011).
3
T. Stergiopoulos, L. M. Arabatzis, G. Katsaros, and P. Falaras, Nano Lett. 2, 1259 (2002).
4
5
Tables
Table SI: Photovoltaic parameters of solid-state DSSCs.
a
Photoanode
b
Jsc
Voc
–2
c
Jmax
–2
d
Vmax
e
FF
η
f
(A cm )
(V)
(A cm )
(V)
ZnO NRs/EY
1.94 × 10−3
0.69
1.72 × 10−3
0.42
0.53
0.70
ZnO NRs-Ag/EY
3.49 × 10−3
0.61
3.25 × 10−3
0.43
0.66
1.39
ZnO NRs/N719
2.56 × 10–3
0.52
2.10 × 10–3
0.43
0.68
0.91
ZnO NRs-Ag/N719
4.85 × 10–3
0.61
4.01 × 10–3
0.45
0.61
1.80
(%)
Foot note: The DSSCs performance was evaluated under 100 mW cm–2 simulated AM 1.5 G solar light; aJsc - Short
circuit current density;
b
Voc - Open circuit voltage; cJmax - Maximum photocurrent density; dVmax - Maximum
photovoltage; eFF - Fill factor and fη - Power conversion efficiency; Area of the cell was 1 cm2.
6
Figures and Caption
FIG. S1.
(Colour online) Diffused reflectance spectra of (a) ZnO NRs, (b) sheaf-like-
(ZnO@Ag)NCM, (c) ZnO NRs-eosin-Y, (d) sheaf-like-(ZnO@Ag)NCM-eosin-Y thin films and
absorption spectrum of 0.05 mM eosin-Y in ethanol (e).
7
FIG. S2. (Colour online) XRD patterns of (a) bare ZnO NRs and (b) sheaf-like-(ZnO@Ag)NCM
with 2.5 wt.% Ag.
8
FIG. S3. (Colour online) Photocurrent-time (I-T) profile of solid-state DSSC containing of ZnO
NRss photoanode with TiO2 NPs modified PEO electrolyte (a) and sheaf-like-(ZnO@Ag)NCM
photoanode with TiO2 NPs modified PEO electrolyte (b) sensitized with eosin-Y dye under
simulated AM 1.5 G solar irradiation of 100 mW/cm2. Area of the cell was 1 cm2.
9
FIG. S4. (Colour online) Photocurrent-time (I-T) profile of solid-state DSSCs (a) ZnO NRs
photoanode + TiO2 NPs modified PEO electrolyte and (b) sheaf-like-(ZnO@Ag)NCM photoanode +
TiO2 NPs modified PEO electrolyte based DSSCs sensitized with N719 dye under simulated AM
1.5 G solar irradiation of 100 mW/cm2. Area of the cell was 1 cm2.