Solvent engineering for fast growth of centimetric high-quality CH3NH3PbI3 perovskite single crystals

Article abstract of DOI:10.1039/c6nj00188b

Centimetre-scale CH₃NH₃PbI₃ perovskite single crystals of high structural quality are grown by a new versatile method based on the use of a binary solvent mixture at a temperature as low as 70 °C. The growth rate is fast enough for a millimeter scale seed crystal to grow to the centimeter scale in a few hours.

Full text of DOI:10.1039/c6nj00188b

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Solvent engineering for fast growth of centimetric high-
quality CH3NH3PbI3 perovskite single crystals
Cite this: DOI: 10.1039/x0xx00000x
Zhiliang Ku,a Nguyen Huy Tiep,a,b Bo Wu,a Tze Chien Sum,a Denis Fichou,a,c,d and
Hong Jin Fan.a,*
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
Centimetre-scale CH3NH3PbI3 perovskite single crystals of high structural quality
are grown by a new versatile method based on the use of a binary solvent mixture at
a temperature as low as 70°C. The growth rate is fast enough for a millimeter scale
seed crystal to grow to the centimeter scale in a few hours.
www.rsc.org/
Over the last few years, organoꢀlead trihalide hybrid perovskites CH3NH3PbI3 single crystals.33, 34 The trap density measured in these
(CH3NH3PbX3, X=Cl, Br, I) have generated a tremendous interest in singleꢀcrystalline perovskites is extremely low in the range 109−1010
electronic and photonic applications such as solar cells,1ꢀ9 lasing,10, 11 cmꢀ3, resulting in a high carrier mobility (164±25 cm2 Vꢀ1 sꢀ1) and
13
lightꢀemitting diodes,12,
and photodetectors.14ꢀ16 In particular, long diffusion lengths (>175 ꢁm). These results pave the way toward
perovskite solar cells (PSCs) have now achieved power conversion highꢀperformance PSCs based on waferꢀscale single crystalline
efficiencies (PCE) up to 20.1%,9 following a rapid surge of perovskites.
development since PSC devices were first reported in 2009 with an
However, the above crystal growth methods remain strenuous
efficiency of 3.8% only.17 This makes PSCs highly competitive to and timeꢀconsuming and are not appropriate to largeꢀscale
crystalline silicon and conventional thin film PV technologies using production. Recently, two different research groups observed that, in
CIGS and CdTe. The success of perovskites in solar cells is mainly certain organic solvents, the solubility of CH3NH3PbI3 substantially
due to their superior characteristics including high absorption decreases at elevated temperatures.35, 36 They grew large crystals by
coefficient,18 ambipolar transport properties,19 long carrier diffusion dissolving CH3NH3I and PbI2 into γꢀbutyrolactone (GBL) and
lengths,20 and low intrinsic recombination rates.21 Up to now, PSCs subsequently heating the solution up to 110°C. We describe here a
are exclusively based on microcrystalline and polycrystalline thin fast and convenient method to grow highꢀquality centimetric
films while single crystal devices remain out of reach due to the CH3NH3PbI3 single crystals under mild conditions (70°C) by using a
difficulty in growing large perovskite single crystals. However, more novel solvent engineering approach and fully characterized them.
and more evidences show that grain boundaries, voids and surface
defects within the microcrystalline perovskite films act as traps for
the charge carriers during solar cell operation, thus leading to
reduced PV performances and significant hysteretic effects in JꢀV
curves.22ꢀ25 Therefore, many efforts are being focused on improving
the crystalline quality of the films,26ꢀ29 which is expected to reduce
the overall bulk defect density and mitigate hysteresis by
suppressing charge recombination to finally lead to higher power
conversion efficiencies. It is then clear that the availability of large
centimeter scale perovskite single crystals could afford maximized
device performances in PV cells and other applications.
As early as 1987, it was reported that CH3NH3PbI3 single
crystals can be synthesized in concentrated aqueous solutions of HI
+
acid containing Pb2+ ions and a proportional amount of CH3NH3
ions.30 Following that method, CH3NH3PbI3 large single crystals
have been reported in recent years.31, 32 Since then, other methods
Fig. 1 Photographs of CH3NH3PbI3 precursor solutions with different
concentrations of solvents at (a) 25°C and (b) after heating at 70°C.
based on organic solutions have been developed to grow centimetric
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DOI: 10.1039/C6NJ00188B
In a second step, one tiny black CH3NH3PbI3 crystals is picked
out from a flask and introduced into a new flask containing a fresh
solution of both CH3NH3I and PbI2 precursors with similar
composition as in step one (Fig. 2). The solution is again heated up
to 70°C, thus allowing the crystal seed to further grow in size. By
repeating this heatꢀandꢀpick process, the CH3NH3PbI3 crystals
gradually grow into larger sizes (Fig. 2b). It is noteworthy that the
crystals prepared by this lowꢀtemperature method have a growth rate
as fast as along methods reported previously.35, 36 After only 6 hours
their diameter is close to 1 cm to even reach 1.7 cm after 3 days.
Xꢀray diffraction (XRD) was used to characterize the
crystallinity of the asꢀprepared CH3NH3PbI3 crystals. Figure 3
shows the powder XRD patterns of the CH3NH3PbI3 powder milled
from the large crystals. For comparison, we also calculated the
standard pattern of CH3NH3PbI3 crystal with pure tetragonal phase
(Fig. 3, red pattern). It shows that the main peaks for the asꢀprepared
CH3NH3PbI3 are at 2θ=14.1°, 28.4° and 40.4° (Fig. 3, black pattern).
The position of the main peaks reveal that asꢀprepared CH3NH3PbI3
crystals possess a tetragonal structure. Meanwhile, the clear peaks of
(121) and (022) (splitting from the (111) peak of the cubic phase) at
2θ=23.5° and 2θ=24.5° further confirms that the crystal adopts a
tetragonal phase with high crystalline quality.
Highꢀresolution XRD was also used to examine the CH3NH3PbI3
single crystal. The 2θ scan results (Fig. 3 blue pattern) show only
diffraction peaks from the (112), (020), (224), (040), (336) and (060)
planes at 2θ = 19.89°, 19.99° ,40.43°, 40.63° ,62.44° and 62.76°,
respectively. These peaks reveal that the asꢀprepared large
CH3NH3PbI3 crystal possess a singleꢀcrystalline nature. To confirm
this, pole figures were measured from one of the CH3NH3PbI3
crystal natural facets. The results are in agreement with the pattern
expected for the {010} facet, indicating that the <010> plane is
parallel to the sample surface. By calculating the Euler angles, we
can conclude that this crystal exposes its natural facets {010} and
{112} (Fig. S2).
Scanning electron microscopy (SEM) images of one nonꢀperfect
crystal (Fig. 4 and S3) show that the surfaces of the crystal is not
smooth; some areas are smooth while in other areas, islands and
terraces are obviously seen. The tetragonal islands are indicative of
a layerꢀbyꢀlayer growth mode of the perovskite crystal. During the
simultaneous nucleation and growth of pyramids, tetragonal islands
form on the surface of the crystal, and may evolve into truncated
tetragonal bipyramids with a dominant (100) plane. The steps and
terraces are also seen which can be the boundaries of the growing
truncated tetragonal bipyramids.
In order to examine the thermal stability of the CH3NH3PbI3
single crystals, we used thermogravimetric analysis (TGA) under
nitrogen flow from room temperature up to 600°C (Fig. 5). It has
been reported that CH3NH3PbI3 thin films decompose at
temperatures as low as ≈150°C.26, 36 In contrast the TGA trace of our
perovskite crystals shows no signature of mass loss until 240°C,
indicating a higher thermal stability as compare to thin films.
Beyond 240°C, the crystals undergo a 20% mass loss of HI,
followed by a 6% loss of the CH3NH2 component at 337°C,
indicating a stronger binding of the amine group in the perovskite
matrix than HI. At around 385°C and beyond, the inorganic
precursor PbI2 is gradually sublimed.
Fig. 2 a) Schematic of the twoꢀstep solvent engineering process for the
growth of large CH3NH3PbI3 single crystals. b) Photographs of crystals
obtained after various growth times (20 min to 6 h). c) Front (left) and side
(right) views of a crystal obtained after 3 days (diameter=1.7 cm).
In a first step (Fig. 1a), six flasks are filled with a CH3NH3PbI3
precursor solution constituted by 1 mL of GBL (density=1.14 g mLꢀ
1), 195.5 mg of CH3NH3I (1.23 ×10ꢀ3 mole) and 572.8 mg of PbI2
(1.23×10ꢀ3 mole). Then, various volumes of acetonitrile (respectively
0; 0.2; 0.4; 0.6; 0.8; and 1.0 mL) are added into the six successive
flasks. After being magnetically stirred at room temperature (25°C)
for 1 h, the content of the first flask (without addition of acetonitrile)
remains unclear, indicating that both CH3NH3PbI3 precursors
possess a limited solubility in GBL at 25°C. Interestingly, although
the two CH3NH3PbI3 precursors have a poor solubility in acetonitrile
(ACN),37 the GBL/ACN binary solvent mixture reveals to be a good
solvent and all these solutions look optically clear. When the
solutions are heated to 70°C, within 30 minutes small black crystals
of CH3NH3PbI3 precipitate from the solutions that contain ACN
volumes equal or higher than 0.6 mL (Fig. 1b). The number of
crystals increases as the added ACN volume increases. We note that
the solubility of CH3NH3I and PbI2 precursors in GBL/ACN binary
solvent mixtures is more sensitive to temperature than in pure GBL
(Fig. S1).
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DOI: 10.1039/C6NJ00188B
Finally, the optical properties of the large CH3NH3PbI3
crystal were studied by photoluminescence (PL) spectroscopy.
As shown in Fig 6a, in comparison with the CH3NH3PbI3 thin
film, the PL peak position of the large single crystal shows a
slight red shift (775 nm for thin film and 783 nm for single
crystal). This could indicate a tighter lattice strain in thin film
than single crystal.34 Moreover, the timeꢀdependent PL signals
of single crystal and thin film were measured at their respective
PL peak wavelengths. Biexponential fitting was performed to
determine the carrier dynamics (Fig. 6b). The single crystal
exhibited a fast (τ=4.9±0.1 ns) and slower lifetime (τ=57.0±0.7
ns). The fast one is attributed to the carrier recombination
lifetime on the surface while the slow one is attributed to that
from beneath the surface (in the bulk).34 Meanwhile, only a fast
decay can be observed in the thin film sample (τ=5.1±0.1 ns).
The front face of the crystal would then be similar to a thin film
where the recombination lifetime is strongly influenced by
impurities, surface defects, dangling bonds, thus yielding a
faster lifetime of ≈5 ns. The longer recombination lifetime in
the bulk of the crystal suggests a greatly reduced trap density as
Fig.
3 XRD patterns recorded on CH3NH3PbI3 powder (black) and
centimetric single crystals (blue). The red pattern is calculated for the
perovskite powder.
compared to the surface and that of the polycrystalline thin film
33, 34
and is characteristic of the bulk properties of CH3NH3PbI3
.
b)
a)
Fig. 6 (a) Steadyꢀstate and (b) timeꢀresolved PL spectra of CH3NH3PbI3 thin
films and single crystals. Black lines represent calculated fits.
In summary, we succeeded in growing centimetric
CH3NH3PbI3 perovskite single crystals of highꢀquality using a
convenient novel method based on the use of a ACN/GBL binary
solvent mixture at low temperature (70°C). The XRD analysis and
SEM images confirm that asꢀprepared CH3NH3PbI3 crystals are
single crystals with tetragonal structure. A slow carrier dynamic is
observed on the timeꢀdependent PL signals, which reveals the
lifetime of carriers propagating deeper in the crystal.
Meanwhile, TGA result indicates that the CH3NH3PbI3 single
crystal possess better thermal stability than the common thin
films. Our original solvent engineering method provides new
opportunities towards the use of large CH3NH3PbI3 single
crystals for both fundamental physical studies and
technological applications in PV solar cells.
Fig. 4 Photography (a) and SEM images (bꢀd) of a nonꢀperfect tetragonal
CH3NH3PbI3 crystal. SEM images in (c and d) show magnified view of one
side faces indicated in (b). Refer Figure S1 for an enlarged view of (b).
Acknowledgements
Authors wish to acknowledge the financial supports from the Ministry
of Education AcRF grants MOE2011ꢀT3ꢀ1ꢀ005, MOE2014ꢀT2ꢀ1ꢀ044
MOE2014ꢀT2ꢀ1ꢀ132 and Tier 1 grant (RG115/15), as well as SPMS
collaborative Research Award M4080536. The Singapore National
Fig. 5 Thermal gravimetric analysis (TGA) of the CH3NH3PbI3 Research Foundation through the Singapore–Berkeley Research
Initiative for Sustainable Energy (SinBeRISE) CREATE Program is
also acknowledged.
single crystals.
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16. H. Deng, D. Dong, K. Qiao, L. Bu, B. Li, D. Yang, H.ꢀE. Wang, Y.ꢀB.
Cheng, Z. Zhao, J. Tang and H. Song, Nanoscale, 2015, 7, 4163ꢀ4170.
17. A. Kojima, K. Teshima, Y. Shirai and T. Miyasaka, J. Am. Chem. Soc.,
2009, 131, 6050ꢀ6051.
18. J. H. Im, C. R. Lee, J. W. Lee, S. W. Park and N. G. Park, Nanoscale,
2011, 3, 4088ꢀ4093.
Notes and references
a School of Physical and Mathematical Sciences, Nanyang Technological
University, 637371, Singapore. Email: FANHJ@ntu.edu.sg
b
Interdisciplinary Graduate School, Nanyang Technological University,
19. E. Edri, S. Kirmayer, A. Henning, S. Mukhopadhyay, K. Gartsman, Y.
Rosenwaks, G. Hodes and D. Cahen, Nano Lett., 2014, 14, 1000ꢀ1004.
20. G. Xing, N. Mathews, S. Sun, S. S. Lim, Y. M. Lam, M. Gratzel, S.
Mhaisalkar and T. C. Sum, Science, 2013, 342, 344ꢀ347.
21. C. Wehrenfennig, G. E. Eperon, M. B. Johnston, H. J. Snaith and L. M.
Herz, Adv. Mater., 2014, 26, 1584ꢀ1589.
639798, Singapore.
CNRS, UMR 8232, Institut Parisien de Chimie Moléculaire, F-75005
c
Paris, France.
d
Sorbonne Universités, UPMC Univ Paris 06, UMR 8232, Institut
Parisien de Chimie Moléculaire, F-75005, Paris, France.
22. D. W. deQuilettes, S. M. Vorpahl, S. D. Stranks, H. Nagaoka, G. E.
Eperon, M. E. Ziffer, H. J. Snaith and D. S. Ginger, Science, 2015, 348,
683ꢀ686.
Z. Ku,and N. H. Tiep contributed equally to this work.
23. G.ꢀJ. A. H. Wetzelaer, M. Scheepers, A. M. Sempere, C. Momblona, J.
Ávila and H. J. Bolink, Adv. Mater., 2015, 27, 1837ꢀ1841.
24. J. Kim, S.ꢀH. Lee, J. H. Lee and K.ꢀH. Hong, J. Phys. Chem. Lett.,
2014, 5, 1312ꢀ1317.
† Electronic Supplementary Information (ESI) available : [Experimental
details for perovskite synthesis, thin film deposition, singleꢀcrystal Xꢀray
diffraction and solubility measurement]. See DOI: 10.1039/c000000x/
25. H.ꢀS. Kim and N.ꢀG. Park, J. Phys. Chem. Lett., 2014, 5, 2927ꢀ2934.
26. A. Dualeh, N. Tétreault, T. Moehl, P. Gao, M. K. Nazeeruddin and M.
Grätzel, Adv. Funct. Mater., 2014, 24, 3250ꢀ3258.
27. Z. Xiao, Q. Dong, C. Bi, Y. Shao, Y. Yuan and J. Huang, Adv. Mater.,
2014, 26, 6503–6509.
28. X. Zheng, B. Chen, C. Wu and S. Priya, Nano Energy, 2015, 17, 269ꢀ
278.
29. Y. Zhou, M. Yang, A. L. Vasiliev, H. F. Garces, Y. Zhao, D. Wang, S.
Pang, K. Zhu and N. P. Padture, J. Mater. Chem. A, 2015, 3, 9249ꢀ
9256.
30. A. Poglitsch and D. Weber, J. Chem. Phys., 1987, 87, 6373ꢀ6378.
31. T. Baikie, Y. Fang, J. M. Kadro, M. Schreyer, F. Wei, S. G. Mhaisalkar,
M. Graetzel and T. J. White, J. Mater. Chem. A, 2013, 1, 5628.
32. Y. Dang, Y. Liu, Y. Sun, D. Yuan, X. Liu, W. Lu, G. Liu, H. Xia and
X. Tao, CrystEngComm, 2015, 17, 665ꢀ670.
33. Q. Dong, Y. Fang, Y. Shao, P. Mulligan, J. Qiu, L. Cao and J. Huang,
Science, 2015, 347, 967ꢀ970.
34. D. Shi, V. Adinolfi, R. Comin, M. Yuan, E. Alarousu, A. Buin, Y.
Chen, S. Hoogland, A. Rothenberger, K. Katsiev, Y. Losovyj, X.
Zhang, P. A. Dowben, O. F. Mohammed, E. H. Sargent and O. M.
Bakr, Science, 2015, 347, 519ꢀ522.
35. M. I. Saidaminov, A. L. Abdelhady, B. Murali, E. Alarousu, V. M.
Burlakov, W. Peng, I. Dursun, L. Wang, Y. He, G. Maculan, A.
Goriely, T. Wu, O. F. Mohammed and O. M. Bakr, Nat. Commun.,
2015, 6.
36. Y. Liu, Z. Yang, D. Cui, X. Ren, J. Sun, X. Liu, J. Zhang, Q. Wei, H.
Fan, F. Yu, X. Zhang, C. Zhao and S. Liu, Adv. Mater., 2015, 27, 5176ꢀ
5183.
37. L. Dou, A. B. Wong, Y. Yu, M. Lai, N. Kornienko, S. W. Eaton, A. Fu,
C. G. Bischak, J. Ma, T. Ding, N. S. Ginsberg, L.ꢀW. Wang, A. P.
Alivisatos and P. Yang, Science, 2015, 349, 1518ꢀ1521.
1. H. S. Kim, C. R. Lee, J. H. Im, K. B. Lee, T. Moehl, A. Marchioro, S. J.
Moon, R. HumphryꢀBaker, J. H. Yum, J. E. Moser, M. Gratzel and N.
G. Park, Sci Rep, 2012, 2, 591.
2. M. M. Lee, J. Teuscher, T. Miyasaka, T. N. Murakami and H. J. Snaith,
Science, 2012, 338, 643ꢀ647.
3. J. Burschka, N. Pellet, S. J. Moon, R. HumphryꢀBaker, P. Gao, M. K.
Nazeeruddin and M. Gratzel, Nature, 2013, 499, 316ꢀ319.
4. N. J. Jeon, J. H. Noh, W. S. Yang, Y. C. Kim, S. Ryu, J. Seo and S. I.
Seok, Nature, 2015, 517, 476ꢀ480.
5. M. Liu, M. B. Johnston and H. J. Snaith, Nature, 2013, 501, 395ꢀ398.
6. W. Nie, H. Tsai, R. Asadpour, J.ꢀC. Blancon, A. J. Neukirch, G. Gupta,
J. J. Crochet, M. Chhowalla, S. Tretiak, M. A. Alam, H.ꢀL. Wang and
A. D. Mohite, Science, 2015, 347, 522ꢀ525.
7. X. Li, M. Ibrahim Dar, C. Yi, J. Luo, M. Tschumi, S. M. Zakeeruddin,
M. K. Nazeeruddin, H. Han and M. Grätzel, Nat. Chem., 2015, 7, 703ꢀ
711.
8. H. Zhou, Q. Chen, G. Li, S. Luo, T.ꢀb. Song, H.ꢀS. Duan, Z. Hong, J.
You, Y. Liu and Y. Yang, Science, 2014, 345, 542ꢀ546.
9. W. S. Yang, J. H. Noh, N. J. Jeon, Y. C. Kim, S. Ryu, J. Seo and S. I.
Seok, Science, 2015, 348, 1234ꢀ1237.
10. G. Xing, N. Mathews, S. S. Lim, N. Yantara, X. Liu, D. Sabba, M.
Grätzel, S. Mhaisalkar and T. C. Sum, Nat. Mater., 2014, 13, 476ꢀ480.
11. H. Zhu, Y. Fu, F. Meng, X. Wu, Z. Gong, Q. Ding, M. V. Gustafsson,
M. T. Trinh, S. Jin and X. Y. Zhu, Nat. Mater., 2015, 14, 636–642.
12. X. Y. Chin, D. Cortecchia, J. Yin, A. Bruno and C. Soci, Nat.
Commun., 2015, 6, 7383.
13. S. D. Stranks and H. J. Snaith, Nat Nano, 2015, 10, 391ꢀ402.
14. X. Hu, X. Zhang, L. Liang, J. Bao, S. Li, W. Yang and Y. Xie, Adv.
Funct. Mater., 2014, 24, 7373–7380.
15. S. Zhuo, J. Zhang, Y. Shi, Y. Huang and B. Zhang, Angew. Chem. Int.
Ed., 2015, 54, 5693ꢀ5696.
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TOC entry
NJ-LET-01-2016-000188
Single crystals of size up to 1.7 centimeter are grown at 70°C in a GBL/ACN binary
solvent mixture.