Highly stable hole-conductor-free CH3NH3Pb(I1-xBrx)3 perovskite solar cells with carbon counter electrode

Article abstract of DOI:10.1016/j.jallcom.2018.03.236

In this work, high stable perovskite solar cells (PSCs) based carbon counter electrode were fabricated in the air environment with 30% of humidity, in which the perovskite CH₃NH₃Pb(I_1-xBr_x)₃ were used

Full text of DOI:10.1016/j.jallcom.2018.03.236

Accepted Manuscript
Highly stable hole-conductor-free CH NH Pb(I Br ) perovskite solar cells with
1-x x 3
3
3
carbon counter electrode
Beibei Zong, Wuyou Fu, Huijing Liu, Liwen Huang, Hari Bala, Xiaodong Wang, Guang
Sun, Jianliang Cao, Zhanying Zhang
PII:
S0925-8388(18)31106-X
10.1016/j.jallcom.2018.03.236
JALCOM 45466
DOI:
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 23 December 2017
Revised Date: 6 March 2018
Accepted Date: 19 March 2018
Please cite this article as: B. Zong, W. Fu, H. Liu, L. Huang, H. Bala, X. Wang, G. Sun, J. Cao, Z. Zhang,
Highly stable hole-conductor-free CH NH Pb(I Br ) perovskite solar cells with carbon counter
1-x x 3
3
3
electrode, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.03.236.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Highly stable hole-conductor-free CH NH Pb(I Br )
3
3
1-x
x 3
perovskite solar cells with carbon counter electrode
Beibei Zong, Wuyou Fu*, Huijing Liu, Liwen Huang, Hari Bala*, Xiaodong Wang, Guang Sun,
Jianliang Cao, Zhanying Zhang
School of Materials Science and Engineering; Cultivating Base for Key Laboratory of
Environment-friendly Inorganic Materials in University of Henan Province, Henan Polytechnic
University, Jiaozuo 454000,People’s Republic of China
*To whom correspondence should be addressed. E-mail: fuwy56@163.com; hari@hpu.edu.cn.
AbstractꢀIn this work, high stable perovskite solar cells (PSCs) based carbon counter electrode
were fabricated in the air environment with 30% of humidity, in which the perovskite
CH NH Pb(I Br ) were used as the absorber. We investigated the effect of the different
3
3
1-x
x 3
Br-doping (x=0.00, 0.10, 0.15, 0.20, 0.25, 0.30) on the devices performance and found that the
appropriate amount of Br-doping could effectively improve crystallinity of the perovskite film and
enhance the light absorption. When the doping-ration x was 0.25, the device exhibited the best
2
performance with the efficiency of 9.99% with active area of 0.2cm under the irradiation of 100
2
mW/cm air mass 1.5 global (AM1.5G) sunlight. By electrochemical impedance spectroscopy
-
(
EIS) measurement, we found that the introducing of Br into the perovskite film could reduce the
carrier recombination loss. Finally, the stability test of the PSCs was carried out and the result
showed that the device still keep 96.23% of the initial efficiency after being stored in the air for 56
days (1344 h), which show an excellent stability.
Keyword: Perovskite solar cells; Hole-conductor-free structure; Carbon counter electrode;
Br-doping; Photoelectric properties; Super-long time stability
1
. Introduction
Organic-inorganic metal halide perovskite solar cells (PSCs) are researched extensively and
contribute to a rapid increase of power conversion efficiencies (PCE). The efficiency of the
perovskite (CH NH PbI , MAPbI ) solar cells has dramatically increased from 3.8% to 22.1% in
3
3
3
3
recent years [1-8]. Then most use a methylammonium lead halide (MAPbX , X=halogen) and its
3
1

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mixed-halide crystal analog [2, 9-15] due to high extinction coefficient, excellent am-bipolar
charge mobility, small exciton binding energy, and tunable bandgap [16-18]. To date, various
structures of PSCs have been developed to enhance the photoelectric properties, such as
perovskite-sensitized ML-TiO scaffold and the planar heterojunction PSCs [1, 19]. For the two
2
types, the planar PSCs have serious hysteresis and the real PCE of PSCs is difficult to evaluate,
however, the hysteresis of PSCs can be eliminated by mesoscopic structural PSCs, effectively.
Usually, the arylamine spiro-MeOTAD was applied to act as electron-blocking layer, with gold as
a counter-electrode. However, the widely used arylamine spiro-OMeTAD and Au are not only
expensive but limiting the long-term stability of the device, which hampers the prospects of
commercial developing. For solving this problem, the hole-conductor-free structure was employed
to replace the hole-transfer materials (HTM) improving the performance of PSCs, and the carbon
counter electrode was introduced by scrape-coating. The carbon as counter electrode of PSCs was
initially reported by Han Hongwei at al, which prepared with hole-conductor-free structure and
the PCE was up to 6.64% [20], and it has been developed rapidly in recent years. In order to
further improve the efficiency of PSCs, the researchers have developed different kinds of
perovskite material with different band gap (Eg), to satisfy demand of multi junction laminated
series perovskite solar cell. Such as mixed-cation (5-AVA) (MA) PbI [21] and mixed-anion
x
1-x
3
MAPb(I Cl ) [22, 23] were reported to improve the photoelectric properties of PSCs.
­
In addition,
the other methods used for enhance PSCs performance was reported by changing the BL-TiO2
layer [24, 25]. However, the most of them don’t remove the HTM and still use noble metal as
1-x x 3
­
counter electrode, by which the devices show poor stability. Therefore, there is an urgent need to
develop an alternative method to achieve long-time stability and reduce the fabrication cost of the
PSCs. Based on the consideration, our group fabricated the mixed organic cation
(
(FA) (MA) PbI ) PSCs based on carbon counter electrode, and the preliminary results had been
x 1-x 3
achieved in our previous reports [26].
In the work, the PSCs with hole-conductor-free structure were fabricated via using carbon
counter electrode (C-electrode) to improve the stability of PSCs. In addition, we changed the
constituent of perovskite material by Br-doping to increase the optical absorption, improve crystal
quality and further enhance the performance of PSCs.
2
. Experimental
2

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2
.1. Materials and reagents
Fluorine-doped tin oxide conductive substrates (Shen Zhen Hua Nan XiangCheng Factory);
Hydriodic acid and hydrobromic acid (AR, Tianjin Comiao Chemical Reagent Co., Ltd.);
methylamine solution (40%wt, Tianjin Comiao Chemical Reagent Co., Ltd.); Diethylether (AR,
Yantai Shuangshuang Chemical Co., Ltd.); PbI (99.99%, Xian Baolet co., Ltd.); PbBr (99%,
2
2
Aladdin); DMF (ACS spectrum level 99.8%, Aladdin); Titanium n-butoxide (AR, Tianjin Comiao
Chemical Reagent Co., Ltd.); TiCl (AR, Aladdin); Ethanol (AR, Shanxi Tongjie chemical reagent
4
co., Ltd). Carbon ink (CH-8(MOD2); Jujo printing supplies & technology (pinghu) co., Ltd.).
2
.2. Preparation of MAI and MABr
MAI or MABr was synthesized according to previous reports [27]. Firstly, hydriodic acid or
hydrobromic acid (30 ml, 45%wt aqueous solution) was slowly added into the methylamine
solution or methylamine solution (27.86 ml, 40%wt in ethanol) in atmosphere under stirring in ice
o
bath for 2 h. Then, the solution was rotary evaporated at 50 C for 1 h. The resultant white
precipitate was got and washed by diethylether for three times to remove impurities. Lastly, the
o
MAI or MABr was obtained and dried at 60 C for 24 h.
2
.3. The preparation of MAPb(I Br ) perovskite precursor solution
1-x x 3
To prepare the MAPb(I Br ) solution, 1.1525 g PbI and 0.3975 g MAI were mixed and
1
-x
x 3
2
dissolved in 1.5 ml DMF (40% wt MAPbI solution) under stirring for 2 h. the MAPbBr (40% wt)
3
3
solution was prepared with PbBr and MABr by precisely the same method. Then two kinds of
2
solution were mixed via different ratio x=0.00, 0.10, 0.15, 0.20, 0.25, 0.30.
2
.4. Cell fabrication
The PSCs were fabricated at air environment with 30% humidity. The schematic diagram of
2
fabrication is shown in Fig. 1(A). FTO-coated glass substrates with 25*25 mm were cleaned by
ultrasonic treatment for 15 min in deionized water, acetone, and ethanol, respectively. Then firstly,
the compact-TiO (C-TiO ) layer was fabricated by spin-coating titanium n-butoxide (Ti(OC H ) )
2
2
4
9 4
o
solution at 2500 rpm for 20 s and then calcined at 500 C for 30 min. Secondly, the substrate was
o
soaked in TiCl aqueous solution (0.08 mol\L) at 70 C for 15 min, followed by sintering on
4
o
heating equipment at 500 C for 30 min, and then the C-TiO2 layer was obtained.
Mesoporous-TiO (M-TiO ) layer was fabricated by spin-coating as-prepared TiO paste diluted in
2
2
2
ethanol (1:3, weight ratio) at 3000 rpm for 20 s on FTO/TiO substrate. The TiO pastes contain
2
2
3

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2
1
0 nm TiO nanocrystals, two kinds of ethylcellulose (terpineol and ethanol) [28, 29]. After drying
2
o
o
30 C, samples were gradually heated to 550 C, maintained for 30 min and cooled to room
temperature. The mesoporous-ZrO (M-ZrO ) layer was fabricated by spin-coating as-prepared
2
2
ZrO paste diluted in ethanol (1:2.5, weight ratio) at 4000 rpm for 20 s on FTO/C-TiO /M-TiO
2
2
2
o
substrate, followed by sintering on heating equipment at 550 C for 30 min. The
double-mesoporous-layer was infiltrated with the as-prepared MAPb(I Br ) solution by
1
-x
x 3
o
spin-coating at 3000 rpm for 20 s, and the perovskite film was formed by heating 90 C for 1 h.
Finally, the carbon electrode was prepared using carbon paste by scrape-coating, then heated at
o
2
1
00 C for 15 min. The active area of our device was fixed at 0.2 cm .
2
.5. Characterization
The crystallinity and morphology of the prepared films were characterized by X-ray
diffraction (Bruker-AXS D8 advance diffractometer). SEM (FEI Quanta 250 FEG). The
photo-absorption properties of different perovskite films were measured by UV-Vis
spectrophotometer (Beijing Purkinje General Ins. Co. Ltd., CHINA). A BOS-X-1000G solar
simulator (Chang chun Bo sheng, Com. Inc., CHINA) was used to give irradiance of 100 mW
cm−2 (the equivalent of one sun at AM1.5G, intensity adjust by using PMA2100/PMA2144
Pyranometer (Solar Light Co, Inc., USA)) at the surface of testing cell. The current-voltage
characteristics were investigated by applying external potential bias to the cell and measuring
photocurrent with a Keithley model 2602A digital source meter (Keithley, USA). In addition, the
devices were measured with electro chemical impedance spectrum in 100 mHz–100 kHz
frequency range through electro chemical workstation (Parstat 2273, USA, Princeton).
­
3
. Result and discussion
-
We fabricated MAPb(I Br ) PSCs with a hole-conductor-free structure due to that Br ­doped
1
-x
x 3
can improve the stability of perovskite material. And then the schematic diagram of PSCs
fabrication process is shown in Fig. 1(A). The PSCs were prepared by layer-by-layer deposition
compact-TiO (C-TiO ), mesoporous-TiO (M-TiO ), mesoporous-ZrO (M-ZrO ) and perovskite,
2
2
2
2
2
2
followed by scrape-coated carbon counter electrode (C-electrode). The structure of solar cells was
followed as: FTO/C-TiO /M-TiO /M-ZrO /Perovskite/C-electrode, among which a double layer
2
2
2
of M-TiO and M-ZrO were applied as a scaffold infiltrated with perovskite [30, 31]. The HTM
2
2
and noble metal electrode (Au, Ag) were not used to prepare PSCs. Moreover, the M-ZrO also
2
4

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was used as the hole blocking layer, and the corresponding energy was shown in Fig. 1(B) [32].
The transport of electrons is from high-energy level to low-energy level. After that, the electrons
are injected into conduction band of TiO and finally transfer to FTO. Then, the holes are
2
transferred from low-energy to high-energy level. Therefore, the holes were transferred to
C-electrode recombination with electron and completed the circuit. This process is agreed with
thermodynamic principle, and the device can generate electricity normally.
The effect of Br-doping on crystal structure was investigated by X-ray diffraction (XRD)
measurements. The XRD patterns of MAPb(I Br ) thin films using methylammonium halide
1
-x
x 3
mixture solutions with the ratios of
x=0.00, 0.10, 0.15, 0.20, 0.25, 0.30 are shown in Fig. 2(A).
The XRD patterns of MAPb(I Br ) films are almost similar. It indicated that the crystal structure
1
-x
x 3
-
-
of MAPb(I Br ) perovskite films was obtained by regulating ratios of Br /I was similar with
1
-x
x 3
MAPbI film. The MAPb(I Br ) thin films (x=0, MAPbI ) exhibited the diffraction peaks at 2θ =
3
1-x
x 3
3
o
1
4.07, 20.0, 23.39, 24.47, 28.42, 32.71, 40.50 and 43.03 , which corresponded to the reflection
planes of (110), (112), (211), (202), (220), (312), (224) and (314) of MAPbI with tetragonal
3
perovskite structure [17, 33, 34] and a preferred orientation along (110) plane appeared. The full
width at half maximum (FWHM) of the (110) peaks slightly decreased with the increasing of the
-
Br content from x=0 to x=0.25 in MAPb(I Br ) thin films and the minimum FWHM appeared
1
-x
x 3
when x was 0.25, which indicated that it was beneficial to the crystallinity of perovskite films
-
about the doping of Br .
­However, the value of FWHM increased when the ratios of x was 0.30,
it's possible that the MAPb(I Br ) thin film begin to decompose, and it leads to the reduction of
1
-x
x 3
perovskite crystal. (This result is shown in the scanning images). In addition, for the films of
perovskite treated under the air environment, the residue PbI was always obviously found in the
2
XRD diffraction pattern, which indicated that the MAPb(I Br ) films maybe were decomposed
1
-x
x 3
-
to produce PbI after exposure to H O of air. It is worthwhile to note that the radius of
­
Br is
2
2
-
smaller than that of I , the interlayer spacing d will decrease with the increasing of the intercalated
-
Br content in perovskite frameworks. According to the Braggs law of 2dsinθ = n
λ
, the decrease of
the interlayer spacing d implied that the 2θ values of the (110) peak should increase with the
-
increasing of the Br content in MAPb(I Br ) thin films. Therefore, diffraction peak of
1
-x
x 3
perovskite toward large angle shift was observed, and the shifting of diffraction peaks was
observed as shown as Fig. 2(B).
5

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Fig. 2(C) shows the absorption spectra of MAPb(I Br ) thin films with the ratios of x=0.00,
1-x
x 3
0
.10, 0.15, 0.20, 0.25, 0.30 ranging wavelength from 500 to 900 nm. As can be seen from the
graph, the MAPbI perovskite thin film shows lower absorption intensity in broader wavelength
3
-
range, and it indicates that the MAPbI perovskite film has poor crystallization. When the Br is
3
doped in the perovskite films, the MAPb(I Br ) thin film absorption edge shifts to shorter
1
-x
x 3
wavelength with the increasing of x value. According to the traditional orbital hybridization theory,
the Valence band is composed of Pb (6s) orbitals and halogen (np) orbitals, while the conduction
band is composed of Pb (6p) orbitals. Because the energy level of Br (4p) is lower than that of I
-
(
5p), the band gap of MAPb(I Br ) changes with the increase of the ratio of Br [35]. Then the
1-x x 3
MAPb(I Br ) thin film presented stronger absorption intensities with the ratios increasing of x
1-x
x 3
from 0.10 to 0.25, and the possible reasons for this higher absorption intensity are that the quality
of perovskite films has been improved. However, the intensity of optical absorption decreased
when the x further increased to 0.30. This phenomenon is owing to the part of MAPb(I Br )
1
-x
x 3
decomposition, then the perovskite have poor crystallinity and density of coverage. The result is
consistent with XRD and SEM characterization. The above results showed that the highest
absorption intensity was exhibited when the ratios of x was 0.25.
The surface morphology of different MAPb(I Br ) perovskite films was observed by
1
-x
x 3
scanning electron microscopy (SEM). As shown in Fig. 3, the acerose perovskite crystals were
infiltrated in a scaffold of M-TiO and M-ZrO . By comparison, for the MAPbI perovskite thin
2
2
3
films, perovskite crystals aggregated into irregular needle-like and schistose on mesoporous layer
film and a little needle-like perovskite infiltrated in mesoporous scaffold. And that the large-area
mesoporous layer had been observed distinctly. It indicated that the MAPbI perovskite had
3
relative poor crystallization. The morphologies of MAPb(I Br ) perovskite films have a striking
1
-x
x 3
ꢁ
contrast with MAPbI perovskite thin film when additive of Br . When the value of x was 0.10,
3
the density of perovskite on mesoporous layer increased observably and the crystal of perovskite
became smaller than that of MAPbI perovskite film. Furthermore, almost all perovskite became
3
needle-like crystal and infiltrated in mesoporous scaffold. Such the possible reason is as follows:
The XRD patterns show that the crystal structure of MAPbI and MAPbBr are different, and the
3
3
MAPbI and MAPbBr have tetragonal and cubic perovskite phases, respectively. The different
3
3
crystal structure between MAPbI and MAPb(I Br ) leads to different formation and growth
3
1-x
x 3
6

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habits. For the MAPb(I Br ) system, the crystal structure of MAPb(I Br ) system gradually
1
-x
x 3
1-x
x 3
changed from tetragonal phase to cubic phase with the increasing of Br-doping content at room
temperature, and the quality of film was gradually improved [36]. Along with x further increased
from 0.15 to 0.25, the packing density of needle-like perovskite was increased gradually and the
size of perovskite crystal varied very little, and then it can enhance the transport of carrier [37].
The stacking of perovskite crystals began to decrease when x reached 0.30, which was possible
that the film began to decompose. The results correspond with XRD and UV patterns above.
The J-V characteristics curves were obtained in order to investigate the photoelectric
properties of PSCs with different Br-doping. The Fig. 4 shows the J-V curves of MAPb(I Br )
1
-x
x 3
2
PSCs with different ratios of x=0.00, 0.10, 0.15, 0.20, 0.25, 0.30 under the 100 mW/cm (AM
.5G sunlight) illumination, and the detailed photovoltaic parameters are listed in Table 1. The
values of open-circuit voltage (V ), short-circuit current density (J ), fill factor (FF), and PCE of
1
oc
sc
-
the PSCs varied with the different Br content. The V , J FF and PCE of MAPbI PSC are 870.7
oc sc,
3
2
-
mV, 20.94 mA/cm , 0.410 and 7.49%, respectively. As Br was introduced, corresponding devices
showed significant improvement in Voc and PCE. The device with Br-doping achieved the best
photovoltaic performance when x was 0.25, and the V , J , and FF increased to 966.3 mV, 21.17
oc sc
2
mA/cm and 0.488. Furthermore, the PCE of PSC with x=0.25 got to 9.99%, which increased by
3
3% comparing with MAPbI PSCs. The photovoltaic property of device is improved because the
3
addition of Br-doping enhances the perovskite morphology optimization and light absorption.
However, when x reached 0.30, the photoelectric properties of devices dropped down dramatically
and the PCE reduced to 8.9%. This may be because the film of perovskite has poor crystallization
and residual impurity. Finally, the result shows that the PSCs have higher photovoltaic
performance when the x is 0.25.
The electrochemical properties of interfaces have been investigated via a bias voltage about
0
.35 V on dark condition in the work. Fig. 5 shows the representative Nyquist plots with different
Br-doping MAPb(I Br ) PSCs, and corresponding equivalent circuit is presented in Fig. 5 (inset).
1
-x
x 3
In a typical Nyquist plot, the series resistance (Rs) was corresponded with the value of the starting
point of the real part of the Nyquist plot. And that the Rs mainly related to the thin film resistance
of FTO substrate and contact resistance of the perovskite, photo-anode and counter electrode [38,
3
9]. However, for the different Br-doping PSCs, the resistance Rs showed a small value.
7

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Moreover, the high frequency region was corresponded with the resistance (R1) of the
perovskite/carbon electrode interface. The low frequency region in the frequency range was
consistent with the recombination resistance (R2) at the TiO /perovskite interface. A large R2
2
-
indicates that it has a large recombination resistance (R ). The devices with different Br content
rec
had shown a similar resistance between Rs and R1. The main difference of Br-doping solar cells
was the value of R2. This could be observed that resistance (R2) increased from 965.3ꢀ to 2101ꢀ
with the increasing of Br-doping from x=0.10 to 0.25, the resistance (R2) decreased to 1456ꢀ
when x was 0.30, thus that PSC shown a largest Rrec when the value of x was 0.25, indicating the
faster carrier transport and a smaller charge recombination rate at TiO /perovskite interface. Then
2
the lower recombination rate is the key factor in exhibiting high Jsc and Voc [40], which is
consistent with the result given by J-V characteristics curves.­The result indicated that a certain
amount of Br-doping could increase the photo-induced electron density as well as the electrical
conductivity.
In general, the regular structure of PSCs consists of FTO, ETL (electron transfer layer), ML
(mesoporous layer), perovskite, HTM and Au (or Ag) counter electrodes, and the spiro-MeOTAD
was widely used as HTM due to its excellent hole transport ability. Although this kind of device
could obtain the efficiency over 20%, but the disadvantage of instability, high cost and complex
manufacturing process limit their commercial application. Therefore, it is necessary to develop an
alternative method to achieve long-time stability and reduce the fabrication cost of the PSCs. So,
we fabricated the carbon electrode PSCs with HTM–free structure to improve the stability and cut
costs. The PSCs were prepared at air environment with 30% humidity and tested under the
2
irradiation of 100 mW/cm air mass 1.5 global (AM1.5G) sunlight, and then the initial efficiency
of 9.28% was obtained and then the devices were stored in air environment at room temperature
without encapsulation. Afterwards, the stability of PSCs was tested at intervals of one week. The
testing result of long-term stability had been shown in Fig. 6. It can be found that J of PSCs is
sc
almost stable. It is worth noting that the value of V was still rising from 939.3 mV to 974.8 mV,
oc
which increase by 35.5mV comparing with initial V during the whole testing process, proving
oc
the stability of the perovskite itself. Meanwhile, the FF and PCE of PSCs did not obviously
decrease, and the value of PCE was retained 96.23% after 56 days (1344 h). The reason is that the
MAPb(I Br ) perovskite shows a stable cubic phase structure and the decomposition of
1-x
x 3
8

ACCEPTED MANUSCRIPT
perovskite films is slowed down owing to the structure of HTM-free and that the performance of
PSCs is very difficult to be influenced by air humidity owing to the hydrophobic of C-electrode,
so it exhibited stable efficiency. The result of contact angles for H O on carbon in full cells at 0s,
2
o
3
0s and 150s could be seen in Fig. 7(A-C). The value of contact angle is 117°>90 and almost
stable, implying that its hydrophobic surface is nonwetted.
4
. Conclusion
In summary, we successfully fabricated super-long time stability MAPb(I Br ) PSCs with
1
-x
x 3
C-electrode at air environment with high humidity. The PSCs did not use the noble metal
electrode and HTM owning to them are expensive and instability. Then, we perfectly prepared the
high stability and low cost PSCs with high PCE (9.99%) under the air environment with 30%
humidity. Also, we observed that a small quantity of Br-doping could increase the distribution
density and crystallinity of perovskite thin films, decrease the carrier recombination rate and
enhance the PSCs efficiency.­Meanwhile, the PSCs exhibited excellent super-long time stability
during 56 days (1344 h) testing due to the hydrophobic of C-electrode in ambient air under high
humidity and the efficiency still had about 96.23%. Finally, it is worth mentioning that we
employed a simple method to fabricate the PSCs based on C-electrode having a good outlook of
popularization and application, due to the characteristics of low cost, high efficiency and
super-long term stability.
Acknowledgment
This work was supported by the National Natural Science Foundation of China (61474038;
U1704255), Doctoral Science Foundation of Henan Polytechnic University (B2012-012).
9

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Figure Captions:
Fig. 1 (A) the schematic diagram of fabrication and the structure of solar cell, (B) diagram of
energy levels of each functional layer in the device.
Fig. 2 (A) and (B) show the XRD patterns, and (C) UV–vis absorption spectra of the
CH NH Pb(I Br ) thin perovskite films with the different values of x.
3
3
1-x
x 3
Fig. 3 The top-view SEM images of perovskite thin films with the different ratios of x=0.00(A),
.10(B), 0.15(C), 0.20(D), 0.25(E), 0.30(F).
Fig. 4 The J–V curves for PSCs with the different ratios of x=0, 0.1, 0.15, 0.2, 0.25, 0.3 under the
0
-2
simulated AM1.5G solar irradiation of 100mWcm .­
Fig. 5 Nyquist plots of PSC with different Br-doping at 0.35 V in the dark.
­
­
Fig. 6 The changing characters of the device in 1344 h after been fabricated.
Fig. 7 The contact angles for H O on carbon electrode in PSC at 0s (A), 30s (B) and 150s (C).
2
Table 1 Photovoltaics performance of PSCs with different values of x.
Figure:
(A)
(B)
­
Fig. 1
1
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(A)
(B)
(C)
­
Fig. 2
­
1
5

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(A)
(B)
(C)
(D)
(E)
(F)
­
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­Fig. 3­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
­
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6

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­­­­­­­­­­­­­­­­­­­­­­­­­­­­­Fig. 4
­
­
­­­­­­­­­­­­­­­­­­­­­­­­­Fig. 5
­
Fig. 6
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(A)
(B)
(C)
Fig. 7
Table 1
Voc/mV
2
x
JSC/mA/cm
FF
PCEꢆ%ꢇ
0
0
0
0
0
0
.00
.10
.15
.20
.25
.30
20.94
870.7
901.1
934.0
930.8
966.3
948.9
0.410
0.462
0.455
0.468
0.488
0.440
7.49
7.90
8.38
8.68
9.99
8.90
18.96
19.72
19.92
21.17
21.32
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Highlights
ꢀ
ꢀ
The super-long time stability CH NH Pb(I Br ) perovskite solar cells at high humidity.
3 3 1-x x 3
2
The active area of 0.2cm perovskite solar cells were fabricated and obtained 9.99%
efficiency.
ꢀ
ꢀ
Carbon electrode PSCs were prepared without the use of noble metal electrodes (Au, Ag) and
HTM.
The PSCs were prepared with distinct low cost and long-time stabilization characteristics.