Accepted Manuscript 3,4-dihydroxybenzhydrazide as an additive to improve the morphology of perovskite films for efficient and stable perovskite solar cells Huiya Li, Kai Zhu, Kaicheng Zhang, Peng Huang, Dahua Li, Ligang Yuan, Tiantian Cao, Ziqi Sun, Zhendong Li, Qiaoyun Chen, Bo Song, Huifang Zhu, Yi Zhou PII:
S1566-1199(18)30644-X
DOI:
https://doi.org/10.1016/j.orgel.2018.12.012
Reference:
ORGELE 5021
To appear in:
Organic Electronics
Received Date: 15 September 2018 Revised Date:
1 December 2018
Accepted Date: 10 December 2018
Please cite this article as: Huiya Li, Kai Zhu, Kaicheng Zhang, Peng Huang, Dahua Li, Ligang Yuan, Tiantian Cao, Ziqi Sun, Zhendong Li, Qiaoyun Chen, Bo Song, Huifang Zhu, Yi Zhou, 3,4dihydroxybenzhydrazide as an additive to improve the morphology of perovskite films for efficient and stable perovskite solar cells, Organic Electronics (2018), doi: 10.1016/j.orgel.2018.12.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
3,4-dihydroxybenzhydrazide as an additive to improve the morphology of perovskite films for efficient and stable perovskite solar cells a
a
a
a
a
a
a
a
Huiya Li,† Kai Zhu,† Kaicheng Zhang,† Peng Huang, Dahua Li, Ligang Yuan, Tiantian Cao, Ziqi Sun, a
a
b
a
a.
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China. E-mail:
[email protected],
[email protected],
[email protected]
b.
RI PT
a
Zhendong Li, Qiaoyun Chen, Bo Song,* Huifang Zhu* and Yi Zhou*
Analysis and Testing Center, Soochow University, Suzhou, 215123, P. R. China
SC
†These authors contributed equally to this work.
M AN U
HIGHLIGHT
3,4-dihydroxybenzhydrazide containing
GRAPHICAL ABSTR ACT
Lewis base C=O was employed as additive to control the crystallizxation kinetics of perovskite. The grain size of peroveskite enlarged dramatically
with
doping
of
3,4-
dihydroxybenzhydrazide. The power conversion efficiencies of perovskite
solar
cell
dihydroxybenzhydrazide
with
3,4-
incrased
EP
TE D
dramatically and the stability of Pero-
AC C
SCs was also enhanced.
ARTICLEINFO Keywords:
ABSTRACT Morphological engineering plays a very important role to the
perovskite solar cells
perf orm ance of p er ovskite solar cells. In this stud y, 3 ,4-
additive
dihydroxybenzhydrazide employes as an additive in the perovskite
3,4-dihydroxybenzhydrazide mophology
precursor to control the crystallization kinetics. It is found that the doping of 3,4-dihydroxybenzhydrazide led to increase of grain size and decrease of grain boundaries, both of which facilitate charge transportation and suppress charge recombination within the
* Corresponding author E-mail:
[email protected],
[email protected],
[email protected]
1
ACCEPTED MANUSCRIPT photoactive layers. Consequently, the power conversion efficiencies
Among them, Lewis acid or base that can interact with
of the corresponding perovskite solar cells are significantly enhanced,
perovskite (e.g. coordination between C=O or S=O and
and a champion power conversion efficiencies of 17.58% with open
2+
Pb ), are widely applied to control the perovskite
circuit voltage of 1.06 V, short circuit current density of 21.40 mA cm-2
crystallization
or
defect
passivation.
For
example,
and fill factor of 79.1% is achieved, which is 21.5% higher than that
Namyoung Ahn et al. firstly introduced DMSO into the without 3,4-dihydroxybenzhydrazide (14.47%). Moreover, upon doping
solution of perovskite precursor, where adducts of
the stability of the perovskite solar cells is also improved. We believe
PbI2·DMSO and CH3NH3I·PbI2·DMSO due to interaction
other lead-based perovskite systems.
between S=O and Pb / MA were generated. The
RI PT
that the idea demonstrated in this research can also be applied to
formation of intermediate product slowed down the 1. Introduction
crystallization, and thus led to high-quality perovskite films and consequently a high performance of the
organic-inorganic hybrid perovskite, the perovskite solar
corresponding devic [35]. Zhifang Wu et al. reported a
cells (Pero-SCs) have shown great potentials as the next
cationic
SC
Owing to the excellent optoelectronic properties of
2-(6-bromo-1,3-dioxo-1H-
M AN U
additive,
benzo[de]isoquinolin-2(3H)-yl)ethan-1- ammonium iodide
photovoltaic devices, the performance of Pero-SCs relies
(2-NAM), which possesses a planar aromatic group and
very much on the morphology of the photoactive layers.
C=O groups. This molecule can effectively decrease the
The film morphologies including film uniformities, film
crystallization rate, and thus increasing the grain size and
coverage, and crystal size can be effectively improved by
consequently reducing the charge recombination within
annealing in the presence of additives [6, 7]. Besides, it’s
the perovskite films [34]. In addition, the hysteresis
known that the majority of the charge recombination and
behavior of the corresponding Pero-SC was suppressed,
perovskite degradation occur at the grain boundaries and
and the stability was improved. To give a more detailed
interfaces [8-12]. Therefore, the enhanced film qualities of
overview
EP
TE D
generation of photovoltaic technology [1-5]. Like the other
of
the
contribution
of
additives
to
the
morphology of the perovskite films as well as the
charge transportation, suppress charge recombination
performance of the corresponding Pero-SCs, studies
and improve the stability of the devices. As known,
using Lewis bases as additives are summarized, as
additives
high
shown in Table 1. PbI2 is a Lewis acid, and the presence
performance Pero-SCs. Up to now, additives reported in
of Lewis base will result in the formation of adduct of
the literature can be divided into several categories:
them two.
AC C
perovskite by utilizing additives are expected to facilitate
can
promote
the
development
of
polymers [13-16], fullerenes [17-19], metal halide salts
The weak interaction between the acid and base plays
[20,21], organic halide salts [22-24], solvent [25-27],
a key role in regulating the crystallinity of the perovskite
inorganic acid [28,29], nanoparticles [30,31] and so on
films. A number of small molecules bearing S, O, N,
[32,33].
especially organic solvents, were employed as additives
2
ACCEPTED MANUSCRIPT Efficiency (%) Device configuration
Addictive
Increasing
Functional group
Ref. Before
After
ratio (%)
16.46
19.7
19.7
16.17
32.0
FTO/bl-TiO2/mp-TiO2/MAPbI3/spiroDMSO
S=O
DMSO
S=O
35
MeOTAD/Ag FTO/bl-TiO2/mp-TiO2/MAPbI3/spiroMeOTAD/Au
NMP
C=O
thiophene
thiophene
37
RI PT
12.25
FTO/c-TiO2/MAPbI3-xClx/spiro-MeOTAD/Au
14.66
19.7
15.3
16.8
16.5
25.9
18.25
8.6
39
19.2
368.3
40
13.1 pyridine
pyridine
urea
C=O
caprolactam
C=O
FTO/c-TiO2/PCBA/FA0.85MA0.15Pb (I0.85Br0.15)3/spiro-MeOTAD/Au
4.1
M AN U
FTO/c-TiO2/mp-
16.80
SC
ITO/SnO2/MAPbI3/spiro-MeOTAD/Ag
TiO2/FA0.83MA0.17PbI2.51Br0.49/spiroMeOTAD/Au FTO/bl-TiO2/FAPbI3/spiro-MeOTAD/Au
38
2-NAM
C=O
18.0
19.33
7.4
36
thiourea
C=S
11.5
13.6
18.26
41
15.92
18.3
15.0
42
C=O,
IT-4F
TE D
FTP/Li-NiOx/MAPbI3/PCBM/BCP/Ag
CN, thiophene
Table 1. Comparisons of perovskite solar cells added with different Lewis bases.
derivative
DMSO [35, 37], pyridine [38] NMP [37], may leave
DOBD) was doped in PEDOT:PSS [43]. As being
residue
applied
after
thermo-annealing,
AC C
even
EP
in the literatures [37]. The organic solvents, such as
which
is
detrimental to the stability of the resulting devices. Only
3,4-dihydroxybenzhydrazide
as
hole
transport
materials,
(denoted
the
by
device
performance was greatly enhanced.
a handful of non-solvent small molecules are reported
In
this
study,
we
introduced
DOBD
into
the
by now. For example, Fang et al.’s study demonstrated
preparation of perovskite precursor. Our results indicate
that IT-4F can improve both the PCE and the stability of
that upon addition of DOBD, the grain size of the
the Pero-SCs. Therefore, exploring small Lewis base as
crystals became bigger and the grain boundaries got
additives is highly required to the development of Pero-
less
SCs [42].
corresponding Pero-SCs was significantly improved due
In our previous study, an easy-accessible catechol
after
annealing.
The
performance
of
the
to the improved charge transportation and suppressed
3
Scheme 1. Schematic illustration of the procedure to prepare perovskite films.
charge recombination. A champion PCE of 17.58%
current density (Jsc) of 21.40 mA cm
-2
SC
with open circuit voltage (Voc) of 1.06 V, short circuit
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ACCEPTED MANUSCRIPT
and fill factor
M AN U
(FF) of 79.1% was achieved. The PCE is 21.5% higher than that (14.47%) without DOBD In addition, the stability was also improved.
2. Results and discussion
Fig. 1 Photos of PbI2 solution in presence of different
concentration of DOBD. The numbers correspond to
TE D
The p-i-n type Pero-SCs with the configuration of
ITO/PEDOT:PSS/perovskite/C60/BCP/Al were fabricated. The details of the device fabrication were
presented in the experimental section. The procedure
EP
to prepare perovskite films was schematically illustrated in Scheme. 1. Briefly, solution 2 was quickly
the concentrations and all the unit is
mg mL-1
Upon addition of DOBD, the solution became clear and
transparent,
which
implies
that
interaction
between DOBD and PbI2 should happen, and the formation of the complex improved the solubility of
dropped on the PbI2 surface without stopping spinning
AC C
PbI2 in DMF (vide infra). In fact, the transparent
of the substrates. Annealing of the substrates at 100
solution is a colloid with nanoparticles, which is
°C for 3 min led to the formation of the crystalize d
confirmed by the observation of Tyndall effect.
perovskite. It is worth to note that an interesting
Furthermore, as the concentration of DOBD was
phenomenon happened during preparation of solution
-1
increased to 5 mg mL , the light pathway became
neat PbI21. As shown in the up row of Fig. 1, the DMF
apparently wider, suggesting the formation of bigger
solution of neat PbI2 was opaque even after being
colloidal particles in the solution. DOBD additives also
stirred at 70 °C for 12 h. This should be attribute d to
made differences on the morphology and diffraction of
t h e r el a tiv el y p o o r s ol u bilit y of P b I 2 i n D M F .
the spin-coated PbI2 films.
4
ACCEPTED MANUSCRIPT
Fig. 3 (a) XRD patterns of annealed and unannealed Fig. 2 SEM images of neat PbI2 (a) and PbI2 with 3 mg -1
RI PT
mL
perovskite films with or without DOBD. (b) FTIR of
DOBD (b); (c) the corresponding X-ray diffraction
DOBD and DOBD+PbI2 for the C=O vibrations.
(XRD) patterns (a) & (b).
film based on PbI2 doped with DOBD increased significantly after annealing. The variation of the peak
(SEM) images in Fig. 2a & 2b, upon addition of 3 mg
intensity and width both are consistent with the other
-1
DOBD, the PbI2 grains became smaller with
results. Without annealing, the peak intensity of the
M AN U
mL
SC
As shown in the scanning electron microscopy
perovskite films decreased upon addition of DOBD,
DOBD). These results are in good agreement with the
and the full-width half-maximum (FWHM) of the peaks
transparency changes. The addition of DOBD caused
increased from 0.12° to 0.19°, both of which indica te
the decrease of grain size of PbI2 in the DMF solution.
that the crystal grains in the film became smaller. With
According to Yang’s research results, the reduced PbI2
annealing, the peak intensity greatly increased and the
particle size should be propitious to the formation of
peak width decreased from 0.12° to 0.09°, both of
high quality of perovskite films [44]. Fig. 2c shows that
which indicate that the crystal size was greatly
the diffraction signal of the samples with DOBD was
increased and crystallinity was improved. It is clear that
much weaker than that without. And according to the
DOBD
EP
TE D
average size of 140 nm (250 nm for PbI2 grains without
can
definitely
regulate
the
crystallization
process of the perovskite films, and this effect should
grains with or without DOBD. The average grain size of
be related to the interactions between DOBD and PbI2.
PbI2 doped with DOBD (18 ± 1 nm) was approximately
In order to investigate the interactions between PbI2
half of PbI2 nanoparticles without doping of DOBD (33
and DOBD, Fourier transform infrared spectroscopy
± 3 nm). The trend was in good accordance to SEM
(FTIR) of DOBD and DOBD + PbI2 were measured,
results.
and the results were shown in Fig. 3b. The sample of
AC C
Scherrer equation, we calculated the size of PbI2
Doping of DOBD also caused great differences to
DOBD+PbI2 was prepared according to the literature -1
the crystallinity of the resulting perovskite films. As
[35]. The peak at 1660 cm
shown in Fig. 3a, the diffraction signal of the perovskite
stretching vibration of C=O bonds of neat DOBD.
film based on neat PbI2 changed slightly after
Being mixed with PbI2, the vibration of C=O bond
annealing, while the diffraction signal of the perovskite
shifted to 1654 cm , which should be attributed to the
-1
5
should be ascribed to the
ACCEPTED MANUSCRIPT weakened bond strength between carbon and oxygen
Nevertheless, as varying the concentration of DOBD
[35], due to the Lewis acid and base adduction
from 0 to 5 mg mL , the peak intensities first increased
interaction
The
and then decreased, and a maximum appeared as the
complexation between DOBD and PbI2 should be
concentration of DOBD was 3 mg mL . The FWHM of
responsible to the passivation of the defects of
the peaks were first decreased and then increased, a
perovskite films during annealing [36].
minimum width was obtained when the concentration
between
Pb
and
C=O
[36,45].
-1
-1
-1
RI PT
of DOBD was 3 mg mL . Both the peak intensity and width of the XRD pattern indicate that 3 mg mL
-1
of
DOBD dopant should be the best in terms of crystallinity and grain size. These results imply that the
SC
crystallinity of the films should be different, and the films doped with 3 mg mL
-1
DOBD may lead to a
M AN U
higher performance.
The effect of DOBD on the morphological change
of perovskite films were investigated by SEM. As shown in Fig. 4c, the perovskite film without DOBD additives consists of many small crystals. Upon
perovskite films doped with different concentrations of
addition of DOBD, the grain size apparently increased,
DOBD. (c) SEM images of the perovskite films
and it reaches to a maximum as the concentration of
prepared with different amount of DOBD additives: 0,
DOBD was 3 mg mL , and further increasing the
1, 2, 3, 4 and 5 mg mL .Scale bar: 2 μm.
concentration did not cause increase of the size. The
-1
TE D
Fig. 4 (a) The UV-vis spectra and (b) XRD patterns of
-1
maximum average diameter was approximately 500
EP
In the following, we systematically studied the
nm. And according to the Scherrer equation, the
dosage effect of DOBD on the perovskite films. As maximum average diameter was 34 ± 3 nm when the
shown in Fig. 4a, the concentrations variation of DOBD
-1
AC C
concentration of DOBD was 3 mg mL . The grain size
did not cause significant change of the UV-vis spectra was increased comparing to the PbI2 nanoparticles
of the resulting perovskite films (after being annealed). doped with DOBD, which is also calculated with
The results indicate that addition of DOBD has very Scherrer equation. Due to the increase of the gain
little effect on the final perovskite, and it is very size,
the
boundaries
per
unit
area
were
possible that interaction between DOBD and PbI2 has correspondingly decreased. According to the study of been replaced by forming perovskite structures. As Wu et al., the grain boundaries act as trap centers and shown in Fig.4b, the diffraction peaks located at 14.08° decelerate the charger transportation from one grain to and 28.45° should be assigned to [110] and [220]
another [36]. Therefore, the reduced grain boundaries
crystal planes of CH3NH3PbI3−xClx perovskite [46].
6
ACCEPTED MANUSCRIPT per
unit
area
result
in
the
improvement
of
the
device
the
device
configuration
was
performances [41]. There is no doubt that the grain
ITO/PEDOT:PSS/perovskite/C60/BCP/Al. The current
size in the horizontal direction was greatly increased.
density- voltage (J-V) and external quantum efficiency
In the normal direction, we can only rely on the XRD
(EQE) curves were shown in Fig. 5a and 5b,
and SEM result to deduce the scale change. Since the
respectively,
XRD results (according to the variation of FWHM)
parameters were listed in Table 2. For the Pero-SCs
implies a increased grain size, and the SEM images
without DOBD, the best PCE achieved was 14.47%
also indicate a increased grain size in the horizontal
with Voc of 0.95 V, Jsc of 20.60 mA cm , and FF of
direction, we assume that the perovskite grains in the
74.7%. For the Pero-SCs with DOBD, the PCE showed
normal direction might also increase accordingly. The
a significant improvement, and a champion PCE of
increase of grain size should facilitate the charge
17.58% with Voc of 1.06 V, Jsc of 21.40 mA cm , and
transportation in the perovskite films.
FF of 79.1% was obtained as 3 mg mL
the
corresponding
photovoltaic
RI PT
and
-2
-1
DOBD was
M AN U
SC
-2
added in the preparation of perovskite precursor. The
propose a possible model for the regulation of
enhancement of PCE of the devices was mainly
perovskite films: (1) The interaction between DOBD
attributed to the enhanced Voc and FF. The Jscs of the
and PbI2 resulted in smaller particles of PbI2, and the
Pero-SCs with or without DOBD didn’t have obvious
reduced size, according to Yang’s study, should be
improvements, and the values were confirmed with
propitious to the formation of high quality perovskite
EQE spectra, as shown in Fig. 5b. The steady-state
films;(2) The formation of adduct between DOBD and
photocurrents and efficiencies of the Pero-SCs were
PbI2 retarded the kinetics for crystal growth instead of
investigated to compare with those indicated by the J-
generating multiple nucleation points, finally resulting
V curves. As shown in Fig. 5c, the bias voltages for the
EP
TE D
Combining the FTIR, XRD and SEM results, we
in larger crystal grain sizes [45]. The model for the
Pero-SCs with and without DOBD were 0.9 and 0.85
formation of perovskite was presented in Scheme. 2.
V, and the steady-state efficiencies were 17.24% and 14.60%, respectively.
AC C
The effect of the DOBD additive on the photovoltaic performance of the Pero-SCs was investigated, where
Scheme 2 The model for the formation of perovskite doped with DOBD.
7
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ACCEPTED MANUSCRIPT
Fig. 5 (a) J−V and (b) EQE curves of the Pero-SCs doped with different amount of DOBD. (c) steady-state photocurrents and efficiencies of the Pero-SCs measured at bias voltage of 0.90 and 0.85 V, respectively.
PCE
To figure out why the addition of DOBD can improve
DOBD (mg mL ) (V) (mA cm ) (%)
(%)
the performance of Pero-SCs, the dark J-V curves and
Jsc
-1
-2
SC
FF
Concentration of Voc
0.95
20.60
74.7 14.47 (14.35 ± 0.28)
photocurrent density-effective voltage (Jph-Veff) plots
1
0.98
20.58
77.4 15.67 (15.48 ± 0.15)
were measured. As shown in Fig. 6a, the Pero-SC
2
1.01
20.94
77.2 16.15 (16.00 ± 0.10)
3
1.06
21.40
79.1 17.58 (17.46 ± 0.11)
4
1.06
20.95
77.2 17.20 (17.14 ± 0.08)
5
1.07
20.81
74.8 16.58 (16.45 ± 0.11)
TE D
M AN U
0
Table 2. Photovoltaic parameters of the Pero-SC with
different concentrations of DOBD additive. The data in
Fig. 6 (a) J-V curves measured in the Dark and (b) JphVeff curves for the Pero-SCs doped with and without DOBD.
EP
the brackets are the average PCEs and deviations.
doped with 3 mg mL-1 DOBD had relatively low leakage current compared with that without DOBD at the
in Table 2. Moreover, the values of steady-state
negative voltages, suggesting that the addition of DOBD
efficiency and photocurrent showed a slight decrease for
in perovskite can effectively suppress the charge
Pero-SC without DOBD under simulation of AM 1.5G
recombination and increase charge extraction, and thus
illumination for 300 s. On the contrary, these two values
resulting in improvement of FF [43,47,48]. Fig. 6b shows
for the Pero-SC doped with DOBD kept constant with
the Jph-Veff plots in double-logarithmic coordinates,
time. The results imply that addition of DOBD in
where Jph was determined by the equation Jph = JL – JD,
perovskite was likely to improve the stability of Pero-SCs
and Veff was calculated from the equation Veff = V0 – V.
under illumination, which
Among the equations, JL and JD were the current
AC C
These results were consistent with the values presented
mainly
results
from
the
densities under illumination and in the dark, respectively,
enhanced quality of the erovskite films.
8
ACCEPTED MANUSCRIPT
RI PT
Fig. 7 (a) Nyquist plots of the Pero-SCs with and without DOBD. (b) Steady-state and (c) transient PL spectra of the perovskite films on PEDOT:PSS surface.
wires, and the arc at the high & low frequency region V is applied voltage and V0 is the voltage at Jph = 0
were regarded as transportation resistance (Rtr) and the [49,50]. As shown in Fig. 6b, the values of Jph increased
SC
recombination resistance (Rrec), respectively [51,52]. linearly with Veff before ~ 0.1 V, and reached to a plateau
Upon the addition of DOBD, the Rtr of Pero-SCs as Veff was ~ 0.3 V. It is clear that Jph of the Pero-SC
decreased drastically from 149.4 to 105.5 Ω, which
M AN U
doped with DOBD was higher than that of Pero-SC
makes a good explanation for the improved charge
without DOBD, leading to a high charge extraction
transportation. Meanwhile, the Rrec was increased
efficiency and consequently a high FF.
from12.5 to 13.6 Ω, which should be responsible for the
The
measurements
of
the
alternating
current
suppression of charge recombination [41]. High Jsc and
impedance spectrometry (ACIS) were performed in the
FF were consequently acquired. The increase in Rrec
dark to analyze the charge transportation abilities of the
TE D
also agrees well with the enhancement of Vocs. Voc is Pero-SCs. The corresponding Nyquist plots and the
function of Jsc and the charge recombination current
corresponding parameters are shown in Fig. 7a and Table 3, respectively. Rtr
(Ω)
(Ω)
Pero-SCs
18.5 149.4 2.2 × 10
With 3 mg mL DOBD 13.3 105.5 1.6 × 10 -1
Rrec
(F)
AC C
Without DOBD
C1
EP
Rs
(Ω)
density (J0), as presented in Equation 1 [53], where A is the ideal factor of a device,
C2
(F)
-8
12.5 1.9 × 10
-6
-8
13.6 1.4 × 10
-6
Kb is the Boltzmann constant, T is the temperature, and e is the elementary charge. Herein, A, Kb, T and e are constants, and Jsc and J0 are variables. The Jsc for Pero-
Table 3. The detailed parameters of the equivalent SCs with and without DOBD were very close to each
circuit obtained by fitting the Nyquist plots of Pero-SCs other. Therefore, the Voc should have a reverse relation with J0. In addition, J0 is a function of Rrec, and they also The data were fitted with the equivalent circuit, as
have a reverse relation [53]. That is to say, Voc should
shown in the inset of Fig. 7a, where the series
be proportional to Rrec..Pero-SCs doped with DOBD
resistances (Rs) was the resistance of electrodes and
showed a higher Rrec, suggesting that the corresponding
9
ACCEPTED MANUSCRIPT Voc should be higher, too. This result was in good
being stored in glove box filled with nitrogen atmosphere
agreement with the device performance.
for 35 days, the PCE of Pero-SC doped with DOBD retained 85%, whereas the Pero-SC without DOBD
photoluminescence (PL) spectra were also used to
decreased down to 70% of its initial efficiency, as shown
investigate the charge extraction and transportation of
in Fig. 8. These results indicated that the stabilities of
the perovskite films. The steady-state PL spectra of the
Pero-SCs were dramatically improved with the doping of
perovskite@PEDOT:PSS were presented in Fig. 7b. For
DOBD.
RI PT
Apart from ACIS, the steady-state and transient
the perovskite films prepared under parallel conditions, the one with DOBD showed much weaker PL intensity, suggesting that the non-emissive decay of fluorescence
SC
increased. These results indicate that DOBD could passivate the defects in the perovskite film effectively. A1 (%) τ1 (ns) A2 (%)τ2 (ns) τavg (ns)
Without DOBD
24.20 16.94 76.81 91.82 87.71
M AN U
Perovskite films
-1
Fig. 8 Normalized PCEs of the Pero-SCs with and
With 3 mg mL DOBD41.07 3.87 58.93 24.36 22.32
without DOBD.
Table 4. The lifetimes and the corresponding portions of
The
transient
PL
TE D
the Pero-SCs with and without DOBD.
spectra
and
3. Conclusions
corresponding
In conclusion, we introduce an additive DOBD
in Fig. 7c and Table 4, respectively. The average charge
containing Lewis base C=O group into perovskite to
carrier lifetimes (τavg) were calculated from the decay
control the crystallization behavior. With the addition of
times (τi) and amplitudes (Ai) using Equation 2 [55]. The
DOBD, the perovskite presented large grain size and
for
the
perovskite
AC C
τavgs
EP
parameters of perovskite@PEDOT:PSS are presented
films
few grain boundaries, which were beneficial to facilitate
without
charge
the
addition
of
DOBD
suppress
charge
skyrocketed to 17.58% with huge enhanced Voc of 1.06 V, Jsc of 21.40 mA cm
Both the quenched emission and shortened τavg indicate upon
and
recombination. The PCE of DOBD doped-Pero-SC
and with DOBD were 87.71 and 22.32 ns, respectively.
that
transportation
the
-2
and FF of 79.1%, which was up
to 21.5% higher than that without DOBD (14.47%). The
charge
conspicuous improvement of PCE mainly resulted from
transportation between the perovskite and PEDOT:PSS
the enhanced Voc and FF. Besides, the DOBD doped-
were improved. At last, the storage stabilities of the
Pero-SCs were much more stable after storing in
Pero-SCs with and without DOBD were compared. After
10
ACCEPTED MANUSCRIPT and stirred at 70 °C for 12
glovebox for 35 days. The PCE of DOBD doped-Pero-
concentration of 460 mg mL
-1
SC retained 85%, whereas the Pero-SC without DOBD
h.
into
decreased down to 70% of its initial efficiency.
concentrations of 0, 1, 2, 3, 4 and 5 mg mL
DOBD
was
added
DMF
with
different
-1
to form a
series of PbI2 / DOBD mixture solutions. These series of 4. Experimental section
solutions are noted as solution 1. The solution of MAI and MACl was prepared by mixing MAI and MACl in
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4.1 Materials isopropanol (IPA, J&K) with the concentration of 50 mg −1
ITO-coated glass (10 Ω sq ) was purchased from
mL and 5 mg mL , respectively, and stirred at 70 °C for
CSG Holding Co., Ltd. PEDOT:PSS (Clevios P VP AI
12 h. This solution is noted as solution 2. The above
4083) was acquired from Nichem Co., and the possible
solution was filtrated with a polyvinyl difluoride (PVDF)
deposition was removed by running through a syringe
filter with typical pore size of 0.45 µm before use. The
-1
SC
-1
PbI2 solution was firstly spin-coated on the above
Methylammonium iodide (MAI) was prepared according
prepared PEDOT:PSS surface at 4500 rpm for 45 s, and
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filter with typical pinholes of 0.45 µm before use.
to the literature [56]. Methylammonium chloride (MACl)
then approximately 45 mL of mixed solution of MAI and
was purchased from Xi’an Polymer Light Technology
MACl was dropped onto the spinning substrate in 20 s.
Crop. PbI2 (99.999%) and 3,4-dihydroxybenzhydrazide
The substrate was then heated at 100 °C for 3 min,
(DOBD) were both acquired from Alfa Aesar. C60 and
obtaining a resulting perovskite film of ∼ 320 nm. Finally,
BCP were purchased from Puyang Yongxin Fullerene
the perovskite films were capped with C60 (∼ 30 nm),
TE D
Technology Co., Ltd. and Alfa Aesar, respectively. 4.2 Device fabrication
BCP (∼ 8 nm) and Al (∼ 80 nm) by thermal evaporation under vacuum of 1.0 × 10
-5
pa with a shadow mask
covered on the slides to define the active area (0.0757
All devices were fabricated on ITO-coated glass
EP
slides with size of 1.5 cm × 1.5 cm. The ITO slides were
2
cm ). The stabilities of Pero-SCs were tested with samples (without encapsulation) stored in glove box
washed in detergent, deionized water, acetone, ethanol filled with nitrogen atmosphere for 35 days.
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and isopropanol for 20 min twice each solvent under 4.3 Characterization
ultrasonification. Then the slides were dried in nitrogen flow, followed by treating with UV-ozone for 20 min.
The surface morphologies of perovskite films were
PEDOT:PSS was spin-coated on the cleaned ITO slides characterized by scanning electron microscopy (SEM, S-
at 5000 rpm for 40 s, and the slides were annealed at 8010, Hitachi) with applied acceleration voltage of 5 kV. 150 °C in air for 15 min.
The crystallinities of PbI2 and perovskite films were
The perovskite films were prepared by a two-step deposition method. PbI2 dimethylformamide
(DMF,
was
collected by X-ray diffraction (XRD) patterns performed
dissolved in N, N-
99.8%,
J&K)
with
on a diffractometer (D2 PHASER, Bruker). The UV-vis
the
absorption spectra were measured using a UV-visible
11
ACCEPTED MANUSCRIPT Notes and references
spectrophotometer (Cary 5000, Agilent Technology). Fourier transform infrared spectroscopy (FTIR) spectra
[1] M. A. Green, A. Ho-Baillie and H. J. Snaith, were recorded on a Bruker VERTEX 70 V. The current Nature Photon, 8 (2014), 506-514. density-voltage
(J-V)
curves
and
steady-state [2] D. Shi, V. Adinolfi, R. Comin, M. Yuan, E.
efficiencies of Pero-SCs were measured on a Keithley Alarousu, A. Buin, Y. Chen, S. Hoogland, 2400 source meter unite under simulated air mass 1.5 Science, 347 (2015), 519-522.
-2
[3] A. (SAN_EI
ELECTRIC,
XEC-300M2).
The
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global (AM 1.5G) solar irradiation at 100 mW cm
Kojima,
external
K.
Teshima,
Y.
Shirai
and
T.
Miyasaka, J. Am. Chem. Soc., 131 (2009), 6050quantum efficiency (EQE) was determined by a QE6051. R3011
system
(Enli
Technology
Co.,
Ltd.).
The
[4] W. S. Yang, B.-W. Park, E. H. Jung, N. J. Jeon,
SC
measurements of the alternating current impedance
Y. C. Kim, D. U. Lee, S. S. Shin, J. Seo, E. K. spectrometry
(ACIS)
were
performed
in the
dark
Kim, J. H. Noh and S. Science, 356 (2017), 1376condition by employing IM6 electrochemical workstation
M AN U
1379.
(Zahner Zennium, Germany) with a bias around the
[5] C. Zuo, H. J. Bolink, H. Han, J. Huang, D. Cahen,
respective open-circuit voltage (Voc). The impedance
L. Ding, Adv. Sci., 3 (2016), 1500324
parameters were analyzed by Z-view software. Steady-
[6] P.-W. Liang, C.-Y. Liao, C.-C. Chueh, F. Zuo, S.
state photoluminescence (PL) spectra were carried out
T. Williams, X.-K. Xin, J. Lin and A. K. Y. Jen,
on FLS 980 (Edinburgh Instrument, UK). Transient PL
Adv. Mater., 26 (2014), 3748-3754.
were
conducted
on
Lifespec
II
TE D
measurements
[7] T. Li, Y. Pan, Z. Wang, Y. Xia, Y. Chen and W.
(Edinburgh Instrument, UK), and the transient PL
Huang, J. Mater. Chem. A, 5 (2017), 12602–
spectra were obtained by monitoring the signal at 780
12652.
EP
nm excited with a 477 nm laser (2 MHz).
AC C
Acknowledgements
[8] Y. Wu, X. Yang, W. Chen, Y. Yue, M. Cai, F. Xie, E. Bi, A. Islam and L. Han, Nat. Energy, 1 (2016), 16148.
This work was supported by National Natural Science
[9] Q. Jiang, L. Zhang, H. Wang, X. Yang, J. Meng,
Foundation of China (51673139), A Priority Academic
H. Liu, Z. Yin, J. Wu, X. Zhang and J. You, Nat.
Program Development of Jiangsu Higher Education
Energy, 2 (2016), 16177.
Institutions,
State
and
Local
Joint
[10] Y. Hou, W. Chen, D. Baran, T. Stubhan, N. A.
Engineering
Luechinger, B. Hartmeier, M. Richter, J. Min, S.
Laboratory for Novel Functional Polymeric Materials.
Chen, C. O. R. Quiroz, N. Li, H. Zhang, T. Heumueller, G. J. Matt, A. Osvet, K. Forberich, Z.-G. Zhang, Y. Li, B. Winter, P. Schweizer, E.
12
ACCEPTED MANUSCRIPT [22] Y. Xie, F. Shao, Y. Wang, T. Xu, D. Wang and F.
Spiecker and C. J. Brabec, Adv. Mater., 28
Huang, ACS Appl. Mat. Interfaces, 7 (2015),
(2016), 5112-5120.
12937-12942.
[11] T. S. Sherkar, C. Momblona, L. Gil-Escrig, J.
[23] M. Yang, T. Zhang, P. Schulz, Z. Li, G. Li, D. H.
Ávila, M. Sessolo, H. J. Bolink and L. J. A. Koster,
Kim, N. Guo, J. J. Berry, K. Zhu and Y. Zhao,
ACS Energy Lett., 2 (2017), 1214-1222.
Nat. Commun., 7 (2016), 12305.
[12] F. Cai, L. Yang, Y. Yan, J. Zhang, F. Qin, D. Liu,
9938
A, 5 (2017), 9402.
RI PT
[24] C. Zuo and L. Ding, Nanoscale, 6 (2014), 9935-
Y.-B. Cheng, Y. Zhou, T. Wang, J. Mater. Chem.
[25] P. Docampo, F.-C. Hanusch, S.-D. Stranks, M.
Huang, S.-Y. Chang, C.-A. Chen, C.-Y. Chao and
D¨oblinger, J.-M. Feckl, M. Ehrensperger, N.-K.
W.-F. Su, ACS Appl. Mat. Interfaces, 7 (2015),
Minar, M.-B. Johnston, H.-J. Snaith and T. Bein,
4955-4961.
Adv. Energy Mater., 4 (2014), 1400355.
SC
[13] C.-Y. Chang, C.-Y. Chu, Y.-C. Huang, C.-W.
[26] L. Li, Y. Chen, Z. Liu, Q. Chen, X. Wang and H.
M AN U
[14] N. Tripathi, Y. Shirai, M. Yanagida, A. Karen and
Zhou, Adv. Mater., 28 (2016), 9862.
K. Miyano, ACS Appl. Mat. Interfaces, 8 (2016),
[27] X. Gong, M. Li, X. Shi, H. Ma, Z. Wang and L.
4644-4650.
Liao, Funct. Mater., 25 (2015), 6671.
[15] Y. Guo, K. Shoyama, W. Sato and E. Nakamura, Adv. Energy Mater., 6 (2016), 1502317.
[28] X. Liu, J. Wu, Y. Yang, T. Wu, Q. Guo, J. Power Sources, 399 (2018), 144-150.
[16] Q. Qin, Z. Zhang, Y. Cai, Y. Zhou, H. Liu, X. Lu,
TE D
X. Gao, L. Shui, S. Wu, J. Liu, J. Power Sources, 397 (2018), 49-56.
[17] J. Xu, A. Buin, A. H. Ip, W. Li, O. Voznyy, R.
EP
Comin, M. Yuan, S. Jeon, Z. Ning, J. J.
Lee and S.-H. Im, Planar Adv. Mater., 27 (2015), 3424-3430.
Zhang, RSC Adv., 6 (2016), 55720.
[18] C.-H. Chiang and C.-G. Wu, Nat. Photonics, 10
AC C
Kim, D. Kim, H.-W. Shin, T.-K. Ahn, C. Wolf, T.
[30] J. Huang, M. Wang, L. Ding, Z. Yang and K.
McDowell, Nat. Commun., 6 (2015), 7081.
(2016), 196-200.
[29] J.-H. Heo, D.-H. Song, H.-J. Han, S.-Y. Kim, J.-H.
[31] S. Li, C. Chang, Y. Wang, C. Lin, D. Wang, J. Lin,
[19] C. Liu, K. Wang, P. Du, C. Yi, T. Meng and X.
C. Chen, H. Sheu, H. Chia, W. Wu, U. Jeng, C.
Gong, Adv. Energy Mater., 5 (2015), 1402024.
Liang, R. Sankar, F. Chou and C. Chen, Energy
[20] K.-M.
Boopathi,
R.
Mohan,
T.
Huang,
Environ. Sci., 9 (2016), 1282-1289.
W.
[32] W. Zhang, M. Saliba, S.-D. Stranks, Y. Sun, X.
Budiawan, M. Lin, C. Lee, K. Ho and C. Chu, J.
Shi, U. Wiesner and H.-J. Snaith, Nano Lett., 13
Mater. Chem. A, 4 (2016), 1591-1597.
(2013), 4505-4510.
[21] S. Bag and M. F. Durstock, ACS Appl. Mater. Interfaces, 8 (2016), 5053-5057.
13
ACCEPTED MANUSCRIPT [33] H. Tsai, W. Nie, P. Cheruku, N.-H. Mack, P. Xu,
[44] K. Yan, M. Long, T. Zhang, Z. Wei, H. Chen, S.
G. Gupta, A.-D. Mohite and H. Wang, Chem.
Yang and J. Xu,. Am. Chem. Soc., 137 (2015),
Mater., 27 (2015), 5570-5576.
4460-4468.
[34] D.-T. Moore, K.-W. Tan, H. Sai, K.-P. Barteau, U.
[45] D. Bi, C. Yi, J. Luo, J.-D. Décoppet, F. Zhang,
Wiesner and L.-A. Estroff, Chem. Mater., 27
Shaik M. Zakeeruddin, X. Li, A. Hagfeldt and M.
(2015), 3197-3199.
Grätzel, Nat. Energy, 1 (2016), 16142. [46] Q. Dong, Z. Wang, K. Zhang, H. Yu, P. Huang, X.
Choi and N.-G. Park, J. Am. Chem. Soc., 137
Liu, Y. Zhou, N. Chen and B. Song, Nanoscale, 8
(2015), 8696-8699.
(2016), 5552-5558.
RI PT
[35] N. Ahn, D.-Y. Son, I.-H. Jang, S. M. Kang, M.
[47] P. K. Nayak, D. T. Moore, B. Wenger, S. Nayak,
Jiang, L. K. Ono, Z. Ning, H. Tian and Y. Qi, Adv.
A. A. Haghighirad, A. Fineberg, N. K. Noel, O. G.
Mater., 30 (2018), 1703670.
Reid, G. Rumbles, P. Kukura, Nat. Commun. 7
SC
[36] Z. Wu, S. R. Raga, E. J. Juarez-Perez, X. Yao, Y.
(2016), 13303.
M AN U
[37] X. Cao, L. Zhi, Y. Li, F. Fang, X. Cui, Y. Yao, L.
[48] S.
Ci, K. Ding and J. Wei, J. Mater. Chem. C, 5
O.
Miguel,
H.-J.
Grande,
V.
Gonzalez-Pedro, R. S. Sanchez, E. M. Barea, I.
(2017), 7458-7464.
Mora-Sero, R. Tena-Zaera, J. Mater. Chem. A , 2
[38] N. K. Noel, A. Abate, S. D. Stranks, E. S. Parrott,
(2014), 12754–12760.
V. M. Burlakov, A. Goriely and H. J. Snaith, ACS
[49] T. Cao, Z. Wang, Y. Xia, B. Song, Y. Zhou, N.
Nano, 8 (2014), 9815-9821.
TE D
[39] J.-W. Lee, S.-H. Bae, Y.-T. Hsieh, N. De Marco, M. Wang, P. Sun and Y. Yang, Chem, 3 (2017), 290-302.
EP
[40] H. Li, Y. Li, Y. Li, J. Shi, H. Zhang, X. Xu, J. Wu,
Chen and Y. Li, ACS Appl. Mat. Interfaces, 8 (2016), 18284-18291. [50] H. Lu, J. Zhang, J. Chen, Q. Liu, X. Gong, S. Feng, X. Xu, W. Ma and Z. Bo, Adv. Mater., 28 (2016), 9559–9566.
H. Wu, Y. Luo, D. Li and Q. Nano Energy, 42 (2017), 222-231.
Chavhan,
[51] D. Liu, J. Yang and T. L. Kelly, J. Am. Chem. Soc., 136 (2014), 17116-17122.
AC C
[41] J. W. Lee, H. S. Kim and N. G. Park, Chem. Res.,
[52] D.-Y. Son, K.-H. Bae, H.-S. Kim and N.-G. Park,
49 (2016), 311-319.
J. Phys. Chem. C, 119 (2015), 10321-10328.
[42] Y. Guo, J. Ma, H. Lei, F. Yao, B. Li, L. J. Mater.
[53] J. Dong, Y. Zhao, J. Shi, H. Wei, J. Xiao, X. Xu, J.
Chem. A, 6 (2018), 5919-5925.
Luo, J. Xu, D. Li, Y. Luo and Q. Meng, Chem.
[43] P. Huang, Y. Liu, K. Zhang, L. Yuan, D. Li, G.
Commun., 50 (2014), 13381−13384.
Hou, B. Dong, Y. Zhou, B. Song and Y. Li, J.
[54] Y.-h. Zhao, K.-c. Zhang, Z.-w. Wang, P. Huang,
Mater. Chem. A, 5 (2017), 24275-24281.
K. Zhu, Z.-d. Li, D.-h. Li, L.-g. Yuan, Y. Zhou and
14
ACCEPTED MANUSCRIPT B. Song, ACS Appl. Mat. Interfaces, 9 (2017), 26234-26241. [55] R. E. Galian, S. G. Carrero and J. Perez-Prieto, J. Mater. Chem. A, 3 (2014), 9187-9193. [56] W. Zhang, M. Saliba, D. T. Moore, S. K. Pathak, M. T. Hörantner, T. Stergiopoulos, S. D. Stranks,
RI PT
G. E. Eperon, J. A. Alexander-Webber, A. Abate, A. Sadhanala, S. Yao, Y. Chen, R. H. Friend, L. A. Estroff, U. Wiesner and H. J. Snaith, Nat.
AC C
EP
TE D
M AN U
SC
Commun., 6 (2015), 6142.
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ACCEPTED MANUSCRIPT Fig. 6 (a) J-V curves measured in the Dark and (b) Jph-Veff curves for the Pero-SCs doped with and without DOBD. Fig. 7 (a) Nyquist plots of the Pero-SCs with and without DOBD. (b) Steady-state and (c) transient PL spectra of Figure Captions the perovskite films on PEDOT:PSS surface. Scam 1 Schematic illustration of the procedure to
without DOBD. Scam 2 The model for the formation of perovskite doped
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Fig. 8 Normalized PCEs of the Pero-SCs with and prepare perovskite films.
Table 1. Comparisons of perovskite solar cells added with DOBD.
SC
with different Lewis bases. Fig.1 Photos of PbI2 solution in presence of different
Table 2. Photovoltaic parameters of the Pero-SC with concentration of DOBD.
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different concentrations of DOBD additive. The data in Fig. 2 SEM images of neat PbI2 (a) and PbI2 with 3 mg -1
the brackets are the average PCEs and deviations.
mL DOBD (b); (c) the corresponding X-ray diffraction
Table 3. The detailed parameters of the equivalent
(XRD) patterns (a) & (b).
circuit obtained by fitting the Nyquist plots of Pero-SCs.
Fig. 3 (a) XRD patterns of annealed and unannealed
Table 4. The lifetimes and the corresponding portions of
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perovskite films with or without DOBD. (b) FTIR of
DOBD (powder) and DOBD+PbI2 (powder) for the C=O vibrations.
Fig. 4 (a) The UV-vis spectra and (b) XRD patterns of
EP
perovskite films doped with different concentrations of DOBD. (c) SEM images of the perovskite films prepared
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with different amount of DOBD additives: 0, 1, 2, 3, 4 and 5 mg mL . Scale bar: 2 μm. -1
Fig. 5 (a) J−V and (b) EQE curves of the Pero-SCs doped with different amount of DOBD. (c) steady-state photocurrents and efficiencies of the Pero-SCs measured at bias voltage of 0.90 and 0.85 V, respectively.
16
the Pero-SCs with and without DOBD.
ACCEPTED MANUSCRIPT
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SC
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Huiya Li, Kai Zhu and Kaicheng Zhang carried out the device fabrication and characterization. Peng Huang and Ligang Yuan carried out the SEM test and analysis. Dahua Li and Tiantian Cao carried out the FTIR characterization and analysis. Ziqi Sun, Zhendong Li and Qiaoyun Chen carried out the ACIS test and analysis. Bo Song, Yi Zhou and Huifang Zhu supervised the work. Bo Song and Kai Zhu analyzed the data and wrote the manuscript with contributions from all the co-authors.