One-step implementation of plasmon enhancement and solvent annealing effects for air-processed

24 Pages·2017·1.65 MB·English

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.
This journal is © The Royal Society of Chemistry 2018
Electronic Supplementary Information
One-step implementation of plasmon enhancement and solvent
annealing effects for air-processed high-efficiency perovskite solar
cells†
Yan Guo,a Xiong He,a Xin Liu,b Xin Li*ab and Leilei Kang*c
a MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion
and Storage, School of Chemistry and Chemical Engineering, Harbin Institute of
Technology, Harbin 150001, China.
b State Key Lab of Urban Water Resource and Environment, Harbin Institute of
Technology, Harbin 150090, China.
c Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023,
China.
*Address correspondence to: [email protected] (X. Li); [email protected] (L.L. Kang)
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Experimental section
2.1 Materials
Cetyl trimethyl ammonium bromide (C H BrN, CTAB, > 99 %) was purchased from
19 42
Sigma-Aldrich. Sodium borohydride (NaBH , 98 %), L-ascorbic acid, hydrogen
4
tetrachloroaurate(III) trihydrate (HAuCl ∙3H O, 99 %), zinc acetate dihydrate
4 2
(Zn(CH COO) ∙2H O, 99.995 %) were obtained from Aladdin. Lead iodide (PbI ,
3 2 2 2
99.999 %) and 4-tert-butypyridine and lithium bis(trifluoromethanesulfonyl)imide (Li-
TFSI, 99.9 %) were acquired from Kanto. Silver nitrate (AgNO , 99.8 %), potassium
3
hydroxide (KOH, 95 %), methylammonium iodide (CH NH I, > 99 %) and 2, 2′, 7, 7′-
3 3
tetrakis-(N, N-di-4-methoxyphenylamino)-9, 9′ spirobifluorene (Spiro-OMeTAD,
99.85 %) were respectively purchased from Energy Chemical, Tianjin Fengchuan
Chemical Reagent Technologies Co., Ltd, Youxuan Trade and Toronto Technologies
Co., Ltd. Other anhydrous solvent were purchased from J&K Chemical. Where all
reagents were used as received without any further purifcation.
2.2 Preparation of ZnO nanoparticles
The ZnO nanoparticles (NPs) were synthesized following a procedure described in our
previous work.1 In a typical procedure, 2.36 g Zn(CH COO) ∙2H O was first dissolved
3 2 2
in 100 mL of methanol solution. Then, 52 mL of KOH methanol solution (354 mM)
was added dropwise into the aforementioned solution. Subsequently, the mixture was
kept at 65 oC for 2.5 h under magnetic stirring, leading to the production of ZnO NPs.
Then, the obtained ZnO NPs were washed with anhydrous methanol for three times to
remove residual precursors. Finally, the ZnO NPs were dispersed into a solution of n-
butanol-chloroform-methanol (14:1:1 volume ratio) to form a 20 mg/mL ZnO NPs
suspension.
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2.3 Preparation of Au nanorods
Au nanorods (NRs) were synthesized by a seed-mediated growth method, according to
a reported procedure with some modification.2 Firstly, 0.6 mL of 10 mM NaBH
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aqueous solution was added to 10 mL of 100 mM CTAB aqueous solution containing 0.25
mM HAuCl under stirring conditions. The mixed solution was vigorous stirred for 10 min
4
before being transferred to a 30 oC water bath where it was left to stay for 12 hours resulting
in a formation of brownish yellow Au seeds solution. In order to synthesize the Au NRs,
1 mL of 10 mM AgNO , 5 mL of 10 mM HAuCl , 1.6/0.8/0.4/0.2 mL of 2 M HCl,
3 4
0.55 mL of 100 mM ascorbic acid and 0.12 mL of Au seeds solution were sequentially
added to 95 mL of 100 mM CTAB aqueous solution, and undisturbedly reacted
overnight under room temperature. The resulting products were collected by centrifugation,
and then the NRs were washed with deionized water for one time. Finally, the equivalent
volume of Au NRs with different aspect ratio was redispersed in N, N-dimethylformamide
(DMF), forming a 0.5 M suspension.
2.4 Fabrication of ZnO-based PSCs
All ZnO-based PSC devices were fabricated on FTO glass substrates (1.5 cm × 2.0
cm). FTO substrates were first etched by zinc powder and 6 M HCl, and ultrasonically
cleaned successively with detergent, deionized water, acetone, 2-propanol, ethanol,
followed by an UV-ozone treatment for 20 min. After that, the electron transport
material was deposited onto the substrates by spin-coating ZnO solution at 500 rpm.
for 3 s and 3000 rpm. for 30 s and dried at room temperature for 10 min. This process
was repeated two times to obtain a compact ZnO film. Then, the ZnO film was aged 24
h under ambient conditions. Subsequently, the Au NRs DMF suspension (0.5 M) was
spin-coated onto the surface of FTO/ZnO at 500 rpm. for 5 s and 1500 rpm. for 60 s
and then dried at 30 oC for 10 min. The perovskite layer was synthesized by a two-step
3
spin-coating fabrication protocol. The PbI DMF solution (460 mg /mL) was first spin-
2
coated on the FTO/ZnO film at 3000 rpm. for 30 s and annealed at 70 oC for 10 min.
Then, a solution of CH NH I in 2-propanol (50 mg/mL) was spin-coated on the surface
3 3
of PbI film at 1000 rpm. for 5 s and 3000 rpm. for 25 s and annealed at 80 oC for 30
2
min in a closed petri dish to form a highly crystalline and compact without pinhole
CH NH PbI (MAPbI ) layer. After the FTO/ZnO/Au NRs/MAPbI films were cooled
3 3 3 3 3
down to the room temperature, the Spiro-OMeTAD hole transfer layer (80 mg of
Spiro-OMeTAD, 28.5 μL 4-tert-butypyridine, 17.5 μL Li-TFSI (520 mg of Li-TFSI in
1 mL of acetonitrile) all dissolved in 1 mL chlorobenzene) was deposited on the top of
FTO/ZnO/MAPbI film by spin-coating at 4000 rpm. for 30 s. Finally, about 60 nm
3
thick Au counter electrode was deposited on top of Spiro-OMeTAD film via vacuum
thermal evaporation at an evaporation rate 1.0 Å/s. As a control experiment, the PSC
devices without Au NRs were fabricated under the same fabrication conditions as well.
In order to further investigate the possible improvement mechanisms of perovskite
crystal, we also designed and fabricated the films of ZnO/MAPbI , ZnO/Au
3
NRs/MAPbI and ZnO/DMF/MAPbI films according to the above operating
3 3
procedure. The active area of PSCs was confirmed to be 0.12 cm2 by a non-reflective
metal mask. All processes including fabrication, measurement and storage of devices
were carried out under ambient conditions. The environmental temperature and relative
humidity for the fabrication process, J-V measurement and photo-stability investigation
were about 25 oC and 50 %, respectively. The average relative humidity was about 40 %
when studying the long-term ambient atmosphere stability.
2.5 Characterization
X-ray absorption near edge structure (XANES) at the Zn K-edge (9659 eV) were
recorded at the BL14W1, Shanghai Synchrotron Radiation Facility (SSRF), Shanghai
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Institute of Applied Physics (SINAP), China. The energy was calibrated by Zn foil.
The spectra were collected at room temperature via the fluorescence mode. The light
source is portable xenon lamp. X-ray diffraction (XRD) pattern was used to analyze
crystal structure, which was recorded on a Panalytical Empyrean X-ray diffractometer
with a Cu Kα radiation (λ = 1.540598 Å) at a scan rate of 2o/min. The morphologies of
nanoparticles and films as well as the element EDS mappings were analyzed by Cold
Field Emission scanning electron microscopy (SEM, Hitachi, SU8000) and
transmission electron microscope (TEM, JEOL, JEM-2100). Atomic force scanning
probe microscope (AFM, Bruber, Dimension Icon) was used to perform AFM high
image and scanning Kelvin probe microscope (SKPM) tests. Photoluminescence (PL)
spectra and PL mappings were performed on a Renishaw in Via confocal micro-Raman
spectroscopy system (λ = 633 or 532 nm). Ultraviolet-visible (UV-vis) absorption
spectroscopy measurements were conducted on TU1901 spectrometer (Beijing
Purkinje General Instrument Co., Ltd). Static water contact angle was tested using a
JC2000C1 contact angle instrument.
Photocurrent density-photovoltage (J-V) curves of PSCs and conductivity tests were
measured by a binding unit of electrochemical workstation (VersaSTAT 3, Ametek,
USA) and a class ABB solar simulator (model 94021A, Newport, USA), where the
cells were illuminated using an AM 1.5G sunlight (100 mW cm-2) generating from 150
W xenon lamp optical source, and the intensity of light was standardized by a Newport
Oriel standard PV reference cell system (model 91150 V). The scan rate was 0.2 V/s.
Electrochemical impedance spectra (EIS) were performed using a VersaSTAT 3
electrochemical workstation (Ametek, USA) at a frequency ranging from 106 to 0.1 Hz
with 5 mV amplitude in the dark condition. The EIS data was fitted by the software of
ZView2 according to the equivalent circuit model. Incident photon-to-electron
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conversion efficiency (IPCE) was recorded by a QTest Station 500D solar cell
quantum efficiency measurement system (CROWNTECH, USA) equipped with a 300
W tungsten lamp power source, a QEM11-S 1/8 m monochromator, a Keithley 2000
multimeter and an opaque chamber. Hall data were collected by a Hall 8800 system.
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Table S1 Summary of references about application of Au or Ag NPs in PSCs.
Preparations J V FF PCE
Device structure SC OC Ref.
conditions (mA cm-2) (V) (%) (%)
FTO/ZnO/Au NRs/CHNHPbI/Spiro-OMeTAD/Au 22.52 -1.026 71.45 16.51 Current
3 3 3
In Air
FTO/ZnO/CHNHPbI/Spiro-OMeTAD/Au 20.58 -1.021 68.86 14.47 Work
3 3 3
FTO/c-TiO/Au@SiO-m-AlO/MAPbI Cl/Spiro-OMeTAD/Ag 16.91 -1.02 64 11.4
2 2 2 3 3-x x
Ref. 12
In air
FTO/c-TiO/m-AlO/MAPbI Cl/Spiro-OMeTAD/Ag 14.76 -1.04 67 10.7
2 2 3 3-x x
FTO/c-TiO/m-TiO@Au NSs/Triple cation perovskite/Spiro-OMeTAD/Au N-filled 22.97 -1.08 71 17.72
2 2 2
Ref. 13
FTO/c-TiO/m-TiO/Triple cation perovskite/Spiro-OMeTAD/Au glove box 21.14 -1.05 69 15.19
2 2
FTO/c-TiO/m-TiO-Au@Ag nanocuboids/CHNHPbI Cl/Spiro-
2 2 3 3 3-x x
23.6 -1.04 74.6 18.31
OMeTAD/Au Glovebox Ref. 14
21.13 -1.01 74.1 15.56
FTO/c-TiO/m-TiO/CHNHPbI Cl/Spiro-OMeTAD/Au
2 2 3 3 3-x x
FTO/ZnO/CHNHPbI/mPEG-Au NSs@Spiro-OMeTAD/Ag N-filled 18.65 -1.053 72.59 13.97
3 3 3 2
Ref. 15
FTO/ZnO/CHNHPbI/Spiro-OMeTAD/Ag glove box 17.78 -1.034 69.66 12.49
3 3 3
FTO/c-TiO/p-TiO-Au@TiO NRs/CHNHPbI-Au@TiO NRs/Spiro-
2 2 2 3 3 3 2
23.12 -1.04 75.5 18.24
OMeTAD/Ag Ref. 16
A
17.4 -0.98 73.7 12.59
FTO/c-TiO/p-TiO/CHNHPbI/Spiro-OMeTAD/Ag
2 2 3 3 3
ITO/Au@TiO-TiAc-stabilized TiO/CHNHPbI Cl/Spiro-
2 2 2 3 3 3-x x
N 22.27 -1.009 74.67 16.78
2
OMeTAD/Au Ref. 21
atmosphere 20.78 -1.005 74.26 15.51
ITO/TiAc-stabilized TiO/CHNHPbI Cl/Spiro-OMeTAD/Au
2 2 3 3 3-x x
ITO/NiO/3 nm-thick Au film/CHNHPbI/PC BM/Ag N-filled 15.9 -0.75 48.6 5.1
3 3 3 71 2
Ref. 22
ITO/NiO/CHNHPbI/PC BM/Ag glove box 10.0 -0.87 36.6 2.6
3 3 3 71
ITO/TiO-Au NPs-TiO/CHNHPbI Cl/Spiro-OMeTAD/Ag 19.9 -1.08 76 16.2
x x 3 3 3-x x
Glovebox Ref. 38
ITO/TiO/CHNHPbI Cl/Spiro-OMeTAD/Ag 18.3 -1.00 72 13.2
x 3 3 3-x x
“A” indicates that the operating conditions of device are not mentioned in the literature.
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Fig. S1 Cross-sectional SEM image of a complete device based on the structure of
glass/FTO/ZnO/Au NRs/MAPbI /Spiro-OMeTAD/Au and corresponding EDS line scan of
3
element of O, Si, Sn, Zn, Au, C, N, I and Pb.
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Fig. S2 Statistic distribution histograms of 50 PSC devices with and without Au NRs:
(a) J , (b) V , (c) FF and (d) PCE. The Gaussian fit is provided as a guide to eyes.
SC OC
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J (0.8V )-J (0.8V )
RS OC FS OC
Hysteresis index =
J (0.8V )
RS OC (1)
Equation (1): J (0.8V ) and J (0.8V ) represent photocurrent density at 80 % of Voc for
RS OC FS OC
the reverse scan (RS) and forward scan (FS), respectively.
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