Evolution in surface coverage of CH3NH3PbI3-:XClX via heat assisted solvent vapour treatment and their effects on photovoltaic performance of devices

Article abstract of DOI:10.1039/c6ra18729c

We demonstrate a facile and well controlled heat assisted solvent vapour treatment (HASVT) method for the growth of compact perovskite layers with good surface coverage areas in ambient atmosphere. The structural and optical properties of the as deposited and solvent vapour treated films have been investigated using SEM, XRD, UV-Vis and PL spectroscopy. Furthermore, photovoltaic devices in layered configuration (FTO/TiO₂/CH₃NH₃PbI_3-XCl_X/P3HT/Ag) are fabricated using as deposited and solvent vapour treated CH₃NH₃PbI_3-XCl_X films. The photoactive perovskite films were treated with chlorobenzene solvent vapour using the HASVT method. The comparative photovoltaic performance of devices fabricated using as deposited and solvent vapour treated CH₃NH₃PbI_3-XCl_X films was assessed. The maximum power conversion efficiency in the case of vapour treatment was estimated to be ～8.05% as compared to the devices fabricated using as deposited films (～5.51%). Our systematic investigations reveal that the enhancement in power conversion efficiency is due to modification in the structural and surface morphology of CH₃NH₃PbI_3-XCl_X films.

Full text of DOI:10.1039/c6ra18729c

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Evolution in surface coverage of CH NH PbI Cl via Heat assisted solvent
3
3
3-X
X
vapour treatment and their effect of device performances
1
2
1†
Dhirendra K. Chaudhary , Pramendra Kumar , Lokendra Kumar
1
Department of Physics, University of Allahabad, Allahabad-211 002, U. P., India
2
Department of Applied Chemistry, IET, M. J. P. Rohilkhand University, Bareilly-243 006, U. P., India
Abstract
We demonstrate a facile and well controlled heat assisted solvent vapour treatment
HASVT) method for the growth of compact perovskite layer with good surface coverage
(
area in ambient atmosphere. The structural and optical properties of as deposited and
solvent vapour treated films have been investigated using SEM, XRD, UV-Vis and PL
spectroscopy.
FTO/TiO /CH
treated CH NH
Furthermore,
photovoltaic
devices
in
layered
configuration
(
2
3
NH
3
PbI3-XCl
X
/P3HT/Ag) are fabricated using as deposited and solvent vapour
3
3
PbI3-XCl
X
films. The photoactive perovskite films were treated with
chlorobenzene solvent vapour using HASVT method. The comparative photovoltaic
performance of devices fabricated using as deposited and solvent vapour treated
3 3 X
CH NH PbI3-XCl films was carried out. The maximum power conversion efficiency in case of
vapour treatment was estimated to be ~8.05% as compared to the devices fabricated using
as deposited films (~5.51%). Our systematic investigations reveal that the enhancement in
power conversion efficiency is due to modification in structural and surface morphology of
3 3 X
CH NH PbI3-XCl films.
†
Corresponding author
Lokendra Kumar
lokendrakr@allduniv.acinlkumarau@gmail.com

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Introduction
Methyl ammonium lead halide perovskite materials has stimulated resurgence of
interest for excellent light to power conversion efficiency and cost effective photovoltaic
1
,2
(
PV) devices . These perovskite photoactive materials exhibit many interesting
optoelectronic properties like ambipolar charge transport, long electron-hole diffusion
3
-6
length and high absorption coefficient with tunable optical band gap . These interesting
properties may lead toa potential high efficiency solar cell device. Since last five years the
organometal halide perovskite based photovoltaic technology is growing very fast and
Formamidinioum lead iodide (FAPbI
3
) based solar cells demonstrate 20% efficiency which is
7
comparable to the commercially available silicon based solar cells .
The power conversion efficiency of the perovskite solar cells are highly dependent
on quality of films such as, surface coverage, grain size distribution, nature of crystallinity
8
-10
and surface morphology . The control over the surface morphology is one of the major
1
1
challenge in order to realize solution processed efficient perovskite solar cell . A large
volume of research have been carried out for achieving high quality perovskite films using
1
2-14
different methods for example- mixed solvent for preparation of perovskite precursor
,
15
16
solute composition , using different humidity for processing , Thermal deposition of
1
17, 18
perovskite layers , optimization of annealing temperature and time
, method of
1
9
20
21
annealing , perovskite film processing steps , solvent treatment of perovskite layer etc.
Among them the modification in perovskite film via solvent treatment is a convenient, facile
and practicable route to get control over solution processed perovskite layer. Recently, in
case of DMSO solvent treatment of perovskite films, Jiang Liu et al. demonstrated high
efficiency solar cells via engineering the crystallite size using solvent annealing method and
22
achieved~13 % power conversion efficiency . Xingtian Yin et al. demonstrated the solution
induced morphology changes in perovskite films and recorded ∼13.1 % efficiency in devices
2
3
with inverted architectures . Qi Chen et al. developed Vapor-Assisted Solution Process
(
VASP) method for the growth of compact perovskite layer. This process lead modification in
24
surface morphology as well as the device performances . In same order JiarongLianet al.
also observed the improvement in the surface morphology via organic solvent vapor
8
treatment using DMSO and DCB as treating solvent . Although, these treatment methods

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provides better film quality of photoactive layer but shown a lack of control over solvent
treatment.
Recently, we have developed an indigenous setup of heat assisted solvent vapour
treatment (HASVT) for controlled solvent treatment of small molecule organic
2
5
semiconducting material . It is important to note that the adopted technique was
successful in achieving controlled solvent vapour treatment that modify the ZnPc film
surface roughness at nanoscale also.
Here, we demonstrate a new technique of heat assisted solvent vapour treatment
(
HASVT) for the manipulation of surface coverage and morphology of CH NH PbI Cl layer
3 3 3-X X
and get improvement in photovoltaic performance. Using this technique the improvement
in the surface coverage (84.30 from 98.96 %) in relative humid environment with humidity
4
5 (±2) % was observed. Not only the surface modification, the larger grain boundaries (2-3
m) and large crystallite size with preferential c-axis growth in perovskite films has been
ꢀ
achieved after solvent vapour treatment.
Furthermore, perovskite solar cells was fabricated in conventional device
architecture (FTO/TiO
2 3 3 X
/CH NH PbI3-XCl /P3HT/Ag) using P3HT as hole transport layer. A
significant improvement (31.51 %) in the power conversion efficiency (η %) was achieved in
the devices after solvent vapour treatment of CH
3
NH
3
PbI3-XCl
X
layer as compared to as
grown films. After solvent vapour treatment of CH
3
NH
3
PbI3-XCl
X
films the η∼ 8.05 % with
2
short circuit current density (JSC) 21.37 mA/cm , open circuit voltage (VOC) 0.8 V and fill
factor 0.47 was obtained. This enhancement in device performance can be attributed to the
improvement in the surface coverage, and crystalline nature of the perovskite layer after
solvent vapour treatment.
Experimental details
Synthesis of CH NH I
3
3
Methyl ammonium iodide was synthesised by reacting 24 ml of methylamine (33 wt% in
absolute ethanol) with 10 ml of hydroiodic acid (57 wt% in water) in 250 ml round bottom
o
flask at 0 C for 2 h under continuous stirring. The achieved solution was put in a rotary
o
evaporator where the solvent was evaporated at 50 C and yellowish white powder of MAI
(
CH NH I) was obtained which was re-dissolved in 80 ml of absolute ethanol and re-
3 3

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precipitated by addition into 300 ml of diethyl ether. The precipitate was filtered out and
the above step was repeated again for further purification. Finally a white powder of MAI
o
was achieved which was dried in vacuum oven overnight at 70 C.
TiO Precursor solution preparation
2
TiO2 precursor solution was prepared by following steps: firstly 370 μL titanium
isopropoxide was drop wise added into 2.53 ml ethanol under constant stirring, keeping this
solution on stirring, an another solution containing 350 μL diluted HCl (3:1) in 2.53 mL
ethanol was prepared separately. This acidic solution of ethanol was mixed drop wise under
constant stirring in ethanolcontaining titanium isopropoxide. The resulting solution was
stirred for 30 min to yield a homogenous, clear and transparent precursor solution.
Perovskite precursor preparation
Non-stoichiometric precursor solution of CH
molar ratio of methyl ammonium iodied (MAI) to lead chloride (PbCl
Dimethylformamide (DMF). The concentration of PbCl and MAI was kept constant at 0.8 M
3 3 X
NH PbI3-XCl was obtained by dissolving 3:1
2
)in anhydrous N,N-
2
and 2.4 M, respectively. The homogeneous precursor solution was obtained by steering
precursor solution overnight at 60˚ C in relative humidity 45 (±2) %.
Preparation of solar cells
FTO coated glass substrates ofsheet resistivity 7-10 Ω/sq. (Sigma Aldrich) were patterned by
wet etching method usingHCl and Zn metal powder. Then substrates were cleaned
subsequently with deionized water, acetone and isopropanol for 10 min using ultrasonic
o
cleaner and dried in vacuum oven at 100 C for 15 min. Thereafter TiO
2
precursor solution
was spin-coated onto pre-cleaned FTOcoated glass substrates at 2000 rpm for 30 sec, the
coated substrates were first dried at 100˚ C and then sintered at 450˚C for 40 min to get
TiO
2
compact layer.
Perovskite precursor solution was spin coated onto compact TiO
2
films at 5000 RPM for 20
sec. After spin coating of the perovskite layer the films were subjected to heat assisted
solvent vapour treatment (HASVT). Here, the chlorobenzene organic solvent was used for
the treatment of perovskite films.For solvent vapour treatment the perovskite precursor

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coated substrate the film was exposed to the chlorobenzene solvent vapour for 60 sec
optimized time) by keeping the distance constant between substrate and vapour shower 10
(
cm and simultaneously heating the block at 80˚C. After solvent vapour treatment the
perovskite film annealed for 40 min at 90˚C using hot plate in relative humidity 45 (±2) % to
get CH NH PbI Cl film. Then Poly(3-hexylthiophene-2,5-diyl) P3HT hole transport layer
3
3
3-X
X
was deposited onto CH NH PbI Cl layer by spin coating of solution containing 16 mg/ml
3
3
3-X
X
P3HT in chlorobenzene at 2000 RPM for 60 sec. Then the substrates were annealed at 100˚C
for 5 min in vacuum oven for removal of residual solvents. Finally, 100 nm silver top
electrodes was thermally deposited using cross mask at deposition rate of 0.3-0.5 Å/Sec and
-6
base pressure 1x10 Torr. The thickness of the deposited silver films was measured in-situ
using quartz crystal thickness monitor. The active area of device prepared under cross
2
masks was estimated to be 0.04 cm .
Material characterization
Surface morphology of the perovskitefilms were investigated usingZeiss field emission
scanning electron microscope (FE-SEM). Crystalline property of the perovskite films were
recorded at room temperature using Proto A-XRD diffractometer using CuKα (λ=1.054
Å)radiation. Electronic absorption (EA) spectra of the films were obtained usingUnicam 5625
UV-Vis spectrometer. Photoluminescence (PL) spectra were recorded for various samples in
steady-state using Horiba Fluorolog with a 450W Xenon lamp excitation source. All spectra
were corrected for instrumental response using a calibration lamp of known emissivity.
Photovoltaic characterization
Current density–voltage (J–V) measurements were performed under simulated AM 1.5
sunlight, using Photo emission technology, USA (PET-SS50AAA-EM), a class AAA solar
-2
simulator calibrated for 100 mW cm light intensity (in constant intensity mode) using
National Renewable Energy Laboratory (NREL) calibrated silicon reference cell. The External
quantum efficiency (EQE) of the solar cells were recorded using calibrated AM 1.5G solar
photon flux in the spectral range of 300 nm to 800 nm and J–V characteristics were
recorded with a Keithley 2400 sourcemeter with the scanning rate of 0.285 V/s. We

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observed an anomalous hysteresis effect in the devices by changing the sweep direction
from -1 to +1.
Results and discussion
Fig. 1(A) shows the schematic diagram of heat assisted solvent vapour treatment (HASVT)
setup. The setup consist of heating block, solvent container, vapour flow controller and
vapour shower (porosity 0.5 mm) with pipe line of 2.4 cm inner diameter.
Figure1: schematic diagram of (A)heat assisted solvent vapour treatment (HASVT) set up (B)
as deposited perovskite (C) solvent vapour treatment

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The chemical processing of as deposited and solvent vapour treated perovskite films are
shown schematically in Fig. 1 (B) & (C) , respectively.
Figure 2: SEM micrograph of the perovskite layers (A) as deposited (B) Solvent vapour
treated
Fig. 2(a) shows the SEM micrograph of as deposited perovskite films, which shows
the random distribution of perovskite grains size with some ribbon/rod like structures with
large voids. The surface morphology of the as deposited perovskite films are in good
1
7
agreement with report of Qing Zhou et al. It clears from the SEM micrograph that the
surface coverage of perovskite layer consists of large number of voids with different shape
and size over the entire surface. The broad distribution of the perovskite grains can be
clearly seen [see inset Fig. 2(a)] in the as deposited films. Fig. 2(b) shows the surface
morphology of perovskite films grown using chlorobenzene solvent vapour using HASVT
method. Clearly, the vapour treatment affects the surface morphology of the film. A drastic
change in the surface morphology is observed and a very dense perovskite layer with grain
size of 2-3 micrometres can be seen in the samples with vapour treatment [see inset Fig. 2
(
b)]. Bairu Liet. al suggests that the CB vapour help DMF evaporation and accelerate the
26
crystallization and also the process of acceleration via spin coating of anti-solvent is
2
7, 28
proved for one step processing of perovskite films
. So, in case of samples with vapour
treatment, the observed modification in morphology could be due to acceleration in
recrystallization process of perovskite films.

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The surface coverage of perovskite layer has been estimated via ImageJ program using
2
9
threshold function at different location and magnification of the SEM images. The
estimated value of surface coverage for as deposited and solvent vapour treated
CH NH PbI Cl films are 84.30% and 98.98%, respectively. These results provide strong
3
3
3-X
X
3 3 X
evidence that the good quality of CH NH PbI3-XCl films could be achieved through
chlorobenzene solvent vapour treatment using HASTV method.
Figure 3: (A) The absolute and (B) normalized XRD pattern of as deposited, solvent treated
3 3 X
and solvent vapour treated CH NH PbI3-XCl films.
Fig 3(A) shows the XRD pattern of as deposited and solvent vapour treated
films. The diffractions peaks at position 14.1, 28.4, 31.83, 43.2 and 58.9 2θ
degree positions are assigned to the planes of (110), (220), (310), (330) and (440) tetragonal
crystal structure of CH NH PbI . It is interesting to note that no additional peak of PbI or
I has been observed which suggests that the entire surface covered with crystalline
only. The intensity of the characteristic peak for solvent treated CH NH
3 3 X
CH NH PbI3-XCl
3
3
3
2
CH
CH
3
3
NH
NH
3
3
PbI3-XCl
X
3
3
PbI3-
X
X
Cl film are found to be significantly enhanced in comparison to the as grown samples. A
small variation in the FWHM of the prominent peaks corresponding to plane (110) and (220)
is observed, which varied from 0.062 to 0.053 and 0.0680 to 0.0602, respectively. The mean
coherent scattering domain size of crystallites were calculated using Debye–Scherrer

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formula and found to be 130 nm and 150 nm for as deposited and solvent vapour treated
CH NH films respectively. The change in FWHM and enhancement in the intensity
3
3 X
PbI3-XCl
of the peak profile may be due to larger crystallite size and dense perovskite layer after
solvent treatment [see Fig. 2 (B)]. To take insight look of XRD data, the normalized XRD data
plots corresponding to peak at position 14.2˚ 2θ value has been shown in fig. 2(B). The
enlarge plot shows some other peaks of very small intensity in as deposited films and
chlorobenzene solution treated films. Interestingly, the relative intensity of peak at position
2
0.04, 24.64, 31.95, 35.09, 40.69 and 60.84 have diminished in solvent vapour treated
CH
CH
3
3
NH
NH
3
PbI3-XCl
PbI3-XCl
X
X
films which suggest that highly oriented crystal domains formation of
form solvent vapour treatment.
3
Note that the surface modification using other techniques like thermal solvent annealing,
and solvent treatment method changes the surface morphology of the films but these
techniques are not able to change the crystallite size. The modification in crystallite size
8
after chlorobenzene treatment has been discussed by JiarongLian et al .
Figure 4: UV-Vis absorption spectra of as deposited and solvent vapour treated
3
3
3 x x
−
CH NH PbI Cl films
Fig. 4 shows the UV-Vis. absorption spectra of the CH NH PbI
3 x
−
Cl films under
3
3
x
3
3
3 x x
−
different processing conditions. The absorption spectra of CH NH PbI Cl films show the
good coverage of solar spectrum from band gap ~ 1.57 eV [calculated from Tauc Plot] with

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considerably sharp absorption edge. Also, the absorption profile that the solvent vapour
treated CH NH samples shows more absorbance in comparison to as grown
3
3 x
PbI3−xCl
samples. The sharper absorption edge and enhanced absorbance could be the due to
combined effect of well-defined crystal morphology, high degree of crystallinity and good
3 3 x
surface coverage of the CH NH PbI3−xCl films.
It is possible that the larger grain size may leads enhancement in the absorbance of vapour
treated films. The large grain size increases the distance of light propagation due to back
3
0-32
scattering of incident light from the comparatively rough surface
.
Figure 5: Photoluminescence spectra of perovskite films processed under different
conditions
Fig. 5 shows the normalized steady state Photoluminescence (PL) emission spectra of
CH
films was recorded by using the excitation wavelength near the absorption band edge. The
CH NH sample without any treatment shows the PL emission peak at 787 nm,
3 3 x
NH PbI3−xCl films on glass substrate under different processing conditions. PL of the
3
3 x
PbI3−xCl
3
3
which shows good agreement with previous reported data . After HASVT treatment of the
film the PL peak blue shifted as compared to the as deposited film and appeared at 783 nm.
A negligibly small change in the FWHM of the PL peak has been observed before and after
the treatment. In general the PL emission is related to the recombination channels
2
2
concerning the band gap and trap state . The observed blue shift with reduced FWHM of PL

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emission of perovskite films could be due to reduction of trap density near the band edge.
The reduction in trap density could be due to larger grain size.
Figure 6: J-V characteristics of device fabricated with (A) as deposited (B) solvent vapour
3 3 X
treated CH NH PbI3-XCl films and (C) External Quantum efficiency spectra (D) JSC
and η with different scan delay.
Fig. 6 (A) and (B) shows the J-V characteristics in forward and backward scan
direction of our best performing devices, fabricated using as deposited and HASVT films,
respectively. The photovoltaic performances of the devices are shown in table 1. The
devices fabricated using CH
3 3 x
NH PbI3−xCl film without any treatment shows η∼3.26% and
∼5.51 % in forward and backward scan respectively, which is in good agreement with others
reports of devices fabricated in ambient atmosphere. Interestingly, the enhancement in the
power conversion efficiency up to η∼7.38 % (in forward scan) and ∼ 8.1% (in backward scan)
is reached in the devices when we use vapour treatment to the perovskite films. The scan
3
4,
direction dependent behaviour in the device is due to existence of anomalous hysteresis
3
5
.
Sufficiently high hysteresis has been observed in J-V curve of devices fabricated with as

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deposited perovskite layer. Whereas, significant passivation in anomalous hysteresis of J-V
characteristics is observe in solvent vapour treated devices.
2
Device
J
SC(mA/cm )
V
OC(V)
FF
η %
3.26
5.51
As deposited
Forward scan
14.63
0.62
0.74
0.36
0.44
Backward scan
16.70
Solvent Vapour
Treated
Forward scan
20.03
21.37
0.79
0.80
0.46
0.47
7.38
8.05
Backward scan
Table 1: Photovoltaic performance of the devices fabricated with as deposited and solvent
vapour treated CH NH films.
3
3 X
PbI3-XCl
To compare the hysteresis in both devices the hysteresis index (HI) has been estimated
3
6
using hysteresis index formula reported by R. S. Sanchezet al. and shown in equation
(
1
.
)
JBS
(
0.5VOC
)
− JFS
0.5VOC
(
0.5VOC
)
hysteresis index =
. . .
1
( )
JBS
(
)
Where JFS
OC for forward and backward scan respectively. The value of HI = 0 corresponds to a
device without observable hysteresis, while HI = 1 corresponds to such type of devices
(0.5VOC
)
and JBS
(0.5VOC
)
stands for value of photocurrent density at 50 % of
V
3
6
which possess hysteresis as high as the photocurrent . Using equation
(
1
we estimated the
)
value of HI in both devices and found to be ∼0.440 and ∼0.036 for devices fabricated with as
deposited and solvent vapour treated perovskite films respectively. Here, we observed a
twelve fold reduce in HI after solvent vapour treatment. This reduced anomalous
hysteresis attributes could be due to the reduction in trap states which causes due to
formation compact perovskite films with larger grain size. Whereas the residual hysteresis in
3
5
J-V characteristics of solvent treated devices may be due to ferroelectric properties ,
electro migration of ions or some other factors. Fig. 6(C) shows the external quantum
efficiency (EQE) spectrum of the both devices. The EQE curve starts increasing near 800 nm
in both spectra which is in good agreement with electronic absorption of CH NH PbI Cl . A
3
3
3-X
X

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broad plateau of ∼ 78% (± 2%) in entire visible region is observed in the EQE curve of device
fabricated with solvent vapour treated perovskite films. To check the reproducibility of the
data, we recorded EQE of the four devices and observed almost same profile of EQE
spectrum with small variation. The integrated JSC value was estimated theoretically and
2
found to be ∼19.21mA/cm . Estimated value of JSC is very close to experimentally observed
value of JSC. The observed slightly lower value of current density from EQE may be due the
2
4
surface trap of the TiO
2
electron transporting layer . Whereas the estimated value of
2
current density is found to be ∼12.59mA/cm of device fabricated using perovskite films
without treatment. A large difference in calculated and experimentally observed value of
EQE is observed in the devices fabricated without treatment. This difference may be due to
3
8
the capacitance of the devices . The plot of Power conversion efficiency and J of the
SC
devices fabricated with solvent vapour treated perovskite films with different delay time are
shown in fig. 6 (D). Almost delay independent behaviour in device performance is observed.
Whereas J-V characteristics of the devices fabricated using without treated perovskite films
are highly dependent on scan delay time (data not shown).
Figure 7 shows the efficiency histogram plot of 20 devices fabricated using as
deposited and solvent vapour treated perovskite films respectively, keeping same
processing parameters conditions at same lab conditions. A wide range distribution in
efficiency of the devices fabricated using as deposited perovskite films is observed. This
wide range distribution efficiency could be due to unequal distribution of perovskite layer.
Whereas 95 % of devices shows efficiency very close to best performing device after HASVT
of perovskite films. These results show that the device performance quit consistent and
reproducible after solvent vapour treatment. This consistency and reproducibility in devices
are result of compact perovskite films.

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Figure 7: Histogram of power conversion efficiency of devices fabricated as deposited and
solvent vapour treated CH NH films.
3
3 X
PbI3-XCl
3 3 x
The devices fabricated using HASVT treated CH NH PbI3−xCl films shows power
conversion efficiency up to η ∼ 8.05 % with reduced anomalous hysteresis. The
performances of devices are reproducible and consistent. Note that, these films are
fabricated in the ambient atmosphere without any lithographic and glove box fabrication
3 3 X
processes. The better photovoltaic performance in vapour treatment of the CH NH PbI3-XCl
layer is attributed to the larger grain size and surface coverage. It could be possible that the
larger grain sizes reduce the recombination centres (trap level) and grain boundaries which
reduce possibility of electron and hole recombination processes as a result of photon
excitation. So the larger grain size, compact perovskite layer and enhanced absorbance of
3 3 X
the CH NH PbI3-XCl all these collectively contributed to enhance power conversion
3 3 X
efficiency by the devices fabricated with solvent vapour treated CH NH PbI3-XCl films.
Conclusions
The heat assisted solvent vapour treatment (HASVT) method has been demonstrated for
uniform growth of perovskite layer. A systematic investigation on structural and optical
properties of perovskite layer has been carried out. Our results suggest that the larger
surface coverage and grain size can be obtained in CH
3 3 X
NH PbI3-XCl layer by HASVT method.
These parameter results the blue shift in the PL spectra of the solvent vapour treated

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3 3 X
CH NH PbI3-XCl films. Photovoltaic performances of devices fabricated with as deposited
and films grown with HASVT methods were compared. An enhancement of 33.51% has been
achieved in the devices fabricated using films grown with the HASVT methods. Our results
provide strong evidence that the HASVT method could be potential techniques for the
growth of the high quality active layer for PV devices.
Acknowledgements
The financial support to this work was provided by the Department of Science & Technology
under FTP grant number SERB/F/5521 and DST-FIST grants. We thank P. Kumar, CSIR-NPL,
New Delhi for Perovskite materials and other supports during this work. Author(s)
acknowledge Rahul and R. K. Gupta, Chemical Engineering Department, IIT, Kanpur, India,
for his kind help in EQE measurements.
References
1
2
.
.
M. Liu, M. B. Johnston and H. J. Snaith, Nature, 2013, 501, 395-398.
M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami and H. J. Snaith, Science, 2012, 338, 643-
6
47.
3
4
.
.
M. A. Green, A. Ho-Baillie and H. J. Snaith, Nature Photonics, 2014, 8, 506-514.
G. E. Eperon, S. D. Stranks, C. Menelaou, M. B. Johnston, L. M. Herz and H. J. Snaith, Energy
&
Environmental Science, 2014, 7, 982-988.
N. J. Jeon, J. H. Noh, Y. C. Kim, W. S. Yang, S. Ryu and S. I. Seok, Nature materials, 2014, 13,
97-903.
5
.
8
6
7
.
.
H. J. Snaith, The Journal of Physical Chemistry Letters, 2013, 4, 3623-3630.
W. S. Yang, J. H. Noh, N. J. Jeon, Y. C. Kim, S. Ryu, J. Seo and S. I. Seok, Science, 2015, 348,
1
234-1237.
J. Lian, Q. Wang, Y. Yuan, Y. Shao and J. Huang, Journal of Materials Chemistry A, 2015, 3,
146-9151.
J. Xing, X. F. Liu, Q. Zhang, S. T. Ha, Y. W. Yuan, C. Shen, T. C. Sum and Q. Xiong, Nano letters,
015, 15, 4571-4577.
8
9
.
.
9
2
1
1
0.
1.
J. Chen, T. Shi, X. Li, B. Zhou, H. Cao and Y. Wang, Applied Physics Letters, 2016, 108, 053302.
Q. Chen, H. Zhou, Z. Hong, S. Luo, H.-S. Duan, H.-H. Wang, Y. Liu, G. Li and Y. Yang, Journal of
the American Chemical Society, 2014, 136, 622-625.
1
2.
H.-B. Kim, H. Choi, J. Jeong, S. Kim, B. Walker, S. Song and J. Y. Kim, Nanoscale, 2014, 6,
6
679-6683.
1
1
3.
4.
C. D. Chandler, C. Roger and M. J. Hampden-Smith, Chemical Reviews, 1993, 93, 1205-1241.
P. W. Liang, C. Y. Liao, C. C. Chueh, F. Zuo, S. T. Williams, X. K. Xin, J. Lin and A. K. Y. Jen,
Advanced Materials, 2014, 26, 3748-3754.
1
5.
J. Qing, H.-T. Chandran, Y.-H. Cheng, X.-K. Liu, H.-W. Li, S.-W. Tsang, M.-F. Lo and C.-S. Lee,
ACS applied materials & interfaces, 2015, 7, 23110-23116.
1
1
6.
7.
J. Yang, B. D. Siempelkamp, D. Liu and T. L. Kelly, ACS Nano, 2015, 9, 1955-1963.
Q. Zhou, Z. Jin, H. Li and J. Wang, Scientific reports, 2016, 6.

RSC Advances
Page 16 of 16
View Article Online
DOI: 10.1039/C6RA18729C
1
1
8.
9.
A. Dualeh, N. Tétreault, T. Moehl, P. Gao, M. K. Nazeeruddin and M. Grätzel, Advanced
Functional Materials, 2014, 24, 3250-3258.
F. X. Xie, D. Zhang, H. Su, X. Ren, K. S. Wong, M. Grätzel and W. C. Choy, ACS nano, 2015, 9,
6
39-646.
2
2
0.
1.
H.-L. Hsu, C.-P. Chen, J.-Y. Chang, Y.-Y. Yu and Y.-K. Shen, Nanoscale, 2014, 6, 10281-10288.
N. J. Jeon, J. H. Noh, Y. C. Kim, W. S. Yang, S. Ryu and S. I. Seok, Nat Mater, 2014, 13, 897-
9
03.
2
2.
J. Liu, C. Gao, X. He, Q. Ye, L. Ouyang, D. Zhuang, C. Liao, J. Mei and W. Lau, ACS Applied
Materials & Interfaces, 2015, 7, 24008-24015.
2
2
3.
4.
X. Yin, M. Que, Y. Xing, X. Liu, W. Que and C. Niu, Electrochimica Acta, 2016, 191, 750-757.
Q. Chen, H. Zhou, Z. Hong, S. Luo, H.-S. Duan, H.-H. Wang, Y. Liu, G. Li and Y. Yang, Journal of
the American Chemical Society, 2013, 136, 622-625.
2
5.
D. K. Chaudhary and L. Kumar, Journal of Materials Science: Materials in Electronics, 2016,
DOI: 10.1007/s10854-016-5170-5, 1-6.
2
2
6.
7.
B. Li, T. Jiu, C. Kuang, S. Ma, Q. Chen, X. Li and J. Fang, Organic Electronics, 2016, 34, 97-103.
M. Xiao, F. Huang, W. Huang, Y. Dkhissi, Y. Zhu, J. Etheridge, A. Gray-Weale, U. Bach, Y.-B.
Cheng and L. Spiccia, Angewandte Chemie, 2014, 126, 10056-10061.
N. Ahn, D.-Y. Son, I.-H. Jang, S. M. Kang, M. Choi and N.-G. Park, Journal of the American
Chemical Society, 2015, 137, 8696-8699.
2
8.
2
3
9.
0.
W. Rasband, US National Institutes of Health, 2005.
N. Cheng, P. Liu, S. Bai, Z. Yu, W. Liu, S.-S. Guo and X.-Z. Zhao, Journal of Power Sources,
2
016, 319, 111-115.
Y. Xie, F. Shao, Y. Wang, T. Xu, D. Wang and F. Huang, ACS Applied Materials & Interfaces,
015, 7, 12937-12942.
3
1.
2
3
3
2.
3.
T. Zhang, M. Yang, Y. Zhao and K. Zhu, Nano Letters, 2015, 15, 3959-3963.
C. Wehrenfennig, M. Liu, H. J. Snaith, M. B. Johnston and L. M. Herz, The Journal of Physical
Chemistry Letters, 2014, 5, 1300-1306.
3
3
4.
5.
E. L. Unger, E. T. Hoke, C. D. Bailie, W. H. Nguyen, A. R. Bowring, T. Heumuller, M. G.
Christoforo and M. D. McGehee, Energy & Environmental Science, 2014, 7, 3690-3698.
H. J. Snaith, A. Abate, J. M. Ball, G. E. Eperon, T. Leijtens, N. K. Noel, S. D. Stranks, J. T.-W.
Wang, K. Wojciechowski and W. Zhang, The Journal of Physical Chemistry Letters, 2014, 5,
1
511-1515.
3
6.
R. S. Sanchez, V. Gonzalez-Pedro, J.-W. Lee, N.-G. Park, Y. S. Kang, I. Mora-Sero and J.
Bisquert, The Journal of Physical Chemistry Letters, 2014, 5, 2357-2363.
3
3
7.
8.
Y. Shao, Z. Xiao, C. Bi, Y. Yuan and J. Huang, Nature communications, 2014, 5.
B. Chen, M. Yang, X. Zheng, C. Wu, W. Li, Y. Yan, J. Bisquert, G. Garcia-Belmonte, K. Zhu and
S. Priya, The Journal of Physical Chemistry Letters, 2015, 6, 4693-4700.