Incorporating 4-tert-Butylpyridine in an Antisolvent: A Facile Approach

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Incorporating 4-tert-butylpyridine in Antisolvent: A Facile Approach to Obtain High Efficient and Stable Perovskite Solar Cells Yahan Wu, Xiaoqiang Shi, Xihong Ding, Yingke Ren, Tasawar Hayat, Ahmed Alsaedi, Yong Ding, Pan Xu, and Songyuan Dai ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b16912 • Publication Date (Web): 09 Jan 2018 Downloaded from http://pubs.acs.org on January 9, 2018

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ACS Applied Materials & Interfaces

Incorporating 4-tert-butylpyridine in Antisolvent: A Facile Approach to Obtain High Efficient and Stable Perovskite Solar Cells Ya-Han Wua, Xiao-Qiang Shia, Xi-Hong Dinga, Ying-Ke Rena, Tasawar Hayatc,d, Ahmed Alsaedic, Yong Dinga,*, Pan Xub,*, and Song-Yuan Daia,b,c,* a

Beijing Key Laboratory of Novel Thin-Film Solar Cells, North China Electric Power

University, Beijing, 102206, China b

Key Laboratory of Photovolatic and Energy Conservation Materials, Institute of

Applied Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, 230031, China c

NAAM Research Group, Department of Mathematics, Faculty of Science, King

Abdulaziz University, Jeddah 21589, Saudi Arabia d

Department of Mathematics, Quaid-I-Azam University, Islamabad 44000, Pakistan

*Corresponding author. E-mail: [email protected]. Phone: +86 55165593222 E-mail: [email protected] E-mail: [email protected]. Phone: +86 1061772268

ABSTRACT The synthesis and growth of CH3NH3PbI3 film with controlled nucleation was a key issue for high efficient and stable solar cells. Here, 4-tert-butylpyridine (tBP) was introduced into the CH3NH3PbI3 antisolvent to obtain high quality perovskite layers. In situ optical microscopy, X-ray diffraction patterns were used to prove that tBP significantly suppressed the perovskite nucleation by forming the intermediate phase. In addition, a gradient perovskite structure was obtained by this method, which greatly improved the efficiency and stability of perovskite. A champion power 1

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conversion efficiency (PCE) of 17.41% was achieved via tBP treatment and the high-efficiency device could maintain over 89% of the initial PCE after 30 days at room temperature. KEYWORDS: 4-tert-butylpyridine, antisolvent, a gradient structure, suppressed the nucleation, perovskite solar cells

1. INTRODUCTION Organometal halide perovskite was attractive materials for solar cells due to their ease of fabrication, panchromatic absorption of sunlight and long carrier diffusion length.1 Since it was reported by Miyasaka et al. in 2009 with a power conversion efficiency (PCE) of 3.8%, perovskite solar cells (PSCs) have now achieved significant efficiency over 22%.2, 3 The morphology control of perovskite crystallization was crucial to achieve high efficient and stable perovskite devices and mainly governed by nucleation and crystal growth.4 A variety of methods have been developed to control perovskite crystallization, such as solvent engineering,5, 6 composition modulation,7 additive addition and several other techniques8-12 among which adding additives has turned out to be an effective and simple method. The concept of additive was frequently used in the organometal halide perovskite solar cells to manipulate the morphology of the perovskite layers.13-17 Grätzel et al. added H2O in perovskite precursor solution to grow high quality perovskite film.18 Prak et al. employed dimethyl sulfoxide (DMSO) to form intermediate adducts with Pb2+ to achieve high quality perovskite films with high photovoltaic performance.19 Jen et al. proved that the 1, 8-diiodooctane (DIO) additives facilitated nucleation and modulated the kinetics of crystal growth during crystallization leading to much smoother perovskite morphology.20 Adding additives in precursor could significantly increase the quality of the perovskite film. In spite of smooth perovskite films with fewer defects and larger grains were obtained, PSCs were essentially limited by the drawback of high concentration additives distribution in the active layer, which could lead to unfavourable impact on electron and hole transmission in perovskite layer. Herein,

in

order

to

avoid

these

problems,

the

method

of

adding

4-tert-butylpyridine (tBP) in the antisolvent was adopted. A gradient heterojunction structure was formed through the addition of tBP in antisolvent to enhance perovskite efficiency and stability. On the one hand, tBP suppressed the nucleation of CH3NH3PbI3 by forming an intermediate adduct. The cooperation between the 2


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nitrogen atom on tBP and the Pb2+ on CH3NH3PbI3 resulted in smooth perovskite films with fewer defects and larger grains enabling to prepare devices with superior performance. By doing this, a champion power conversion efficiency of 17.41% was achieved. On the other hand, tBP was employed as a surface modification agent to augment the hydrophobicity of CH3NH3PbI3. As a result, the devices with tBP treatment exhibited slower deterioration rate with the PCE keeping over 89% after 30 days.

2. EXPERIMENTAL SECTION 2.1 Device Fabrication FTO glasses (15 Ω sq-1) were etched with zinc powder and HCl (0.8 M), then washed with detergent, distilled water and acetone, sonicated for 20 min in ethanol. A compact TiO2 blocking layer (bl-TiO2) was deposited on the precleaned FTO by a spray pyrolysis of 0.6 mL titanium isopropoxide and 0.4 mL bis (acetylacetonate) in 7 mL anhydrous isopropanol solution at 460 oC for 40 min. A mesoporous TiO2 layer (mp-TiO2) was coated onto the bl-TiO2/FTO substrate by spin-coating (4000 rpm, 20 s) TiO2 paste (30NR-T, Dyesol), which was diluted with ethanol (1: 5.3, mass ratio). Then the substrates were dried on hotplate at 80 oC and sintered at 510 oC for 30 min. The precursor solution was prepared with 1.2 M PbI2 (99.99%, Alfa Aesar) and CH3NH3I (99.99%, Xi`an Polymer Light Technology Corp.) in 1 mL mixed solvent of DMF (99.5%, Aldrich) and DMSO (99.8%, Aldrich) (8.5:1.5, volume ratio), then the solution was heated at 75 oC for 1.5 h under stirring. 50 µL of perovskite precursor solution was spin-coated on the mp-TiO2/bl-TiO2/FTO substrate at 1200 rpm and 4800 rpm for 10 s and 30 s, respectively. During the second step, the substrate was quickly dripped with 0.75 mL antisolvent with tBP in chlorobenzene (1:100, volume ratio). The as-prepared film was heated at 110 oC for 60 min on a hotplate under the air flow. A hole-transporting layer (HTM) was spin-coated on perovskite film at 3800 rpm for 30 s. Finally, 60 nm gold electrodes were evaporated on top of the device under vacuum.

2.2 Characterization The films morphologies were characterized by a field-emission scanning electron microscope (FE-SEM, sirion200, FEI Corp., Holland). The in situ micrographs were taken during cooling between crossed polarizers from a microscope (DM2500P, Leica, 3



Germany) equipped with a hot-stage (LTSE-420, Linkam, UK) and a camera (Micropublisher 5.0 RTV, Qimaging, Canada). A Fourier transform infrared spectroscopy (Thermo Fisher IS50R, USA) was used to obtain the spectra for CH3NH3PbI3 and CH3NH3PbI3 with tBP treatment in 4000 cm-1-500 cm-1 range. The films of CH3NH3PbI3 and CH3NH3PbI3 fresh samples were measured by X-ray diffraction (XRD, X’Pert Pro, Netherlands) Cu Kα beam (λ=1.54 A). The steady state photoluminescence (PL) measurements were carried out on a Fluorescence Detector (QM 400 and Laser Strobe, Photo Technology International, USA) and a standard 450 W xenon CW lamp and pulsed nitrogen laser, respectively. The time-resolved photoluminescence (TRPL) spectra were collected using a transient state spectrophotometer (F900, Edinburgh Instruments). CH3NH3PbI3, CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3 with tBP in antisolvent were excited with a 660 nm pulsed diode laser with a repetition rate of 2.5 MHz and an excitation intensity of 14 nJ cm-2. The contact properties of perovskite films were characterized by contact angle measuring instrument (OCA15EC, Dataphysics, Germany). The optical properties of CH3NH3PbI3 and CH3NH3PbI3 with tBP in antisolvent were tested on UV-Vis spectrophotometer (U-3900 H, Hitachi, Japan) in the 400-800 nm range. AQ Test Station 2000ADI system (Newport Corporation, USA) was used to measure the incident photon-to-current efficiency (IPCE) of the PSCs. The photocurrent density-voltage (J-V) curves were measured under one sun illumination (AM 1.5G, 100 mW/cm2) with a solar simulator (solar AAA simulator, Oriel USA) equipped with source meter (Keithley 2400) for devices CH3NH3PbI3 and CH3NH3PbI3 with tBP treatment. The active area for each device was 0.09 cm2 and ensured by masking a black mask on the device. With a 50 mV s−1 of scan rate, the applied bias voltages for the reverse scan and forward scan were from 1.2 to − 0.1 V and from − 0.1 to 1.2 V.

3. RESULT AND DISCUSSION The surface morphology of perovskite films prepared with or without tBP in antisolvent were illustrated in Figure 1a and 1b, respectively. Any pinholes could hardly be observed in the both films due to the employment of antisolvent treatment.21 Similar to other additives, we expected to achieve high-quality perovskite films by 4


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means of the antisolvent with tBP. When tBP was added into the antisolvent, there was observable change in the film morphology in terms of grain size compared to pure CH3NH3PbI3 film (Figure 1a, 1b). In addition, lower magnification SEM images of perovskite films were provided in Figure S1, which further proved that CH3NH3PbI3 with tBP treatment had the larger grain sizes than CH3NH3PbI3. It indicated that a negligible amount of tBP in perovskite antisolvent dramatically changed the morphology of CH3NH3PbI3 films. Figure 1c showed the X-ray diffraction patterns (XRD) of CH3NH3PbI3 with tBP and CH3NH3PbI3 films. For both samples, most of the characteristic peaks corresponded well to CH3NH3PbI3.22 However, the intensity of the peaks of CH3NH3PbI3 with tBP was stronger than those of CH3NH3PbI3. By employing this method, the crystallization of perovskite was improved.

c CH3NH3PbI3 with tBP CH3NH3PbI3

intensity（ a.u）

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10

20

30

40

50

60

70

2θ (°)

Figure 1 Top-view scanning electron microscopy (SEM) images of films, (a) CH3NH3PbI3 with tBP, (b) CH3NH3PbI3. (c) X-ray diffraction patterns of (XRD) of CH3NH3PbI3 with tBP or CH3NH3PbI3.

5



K

CH3NH3PbI3with tBP,fresh sample

intensity（ a.u）

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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CH3NH3PbI3,fresh sample

5

10

15

20

25

30

35

40

2θ (°)

Figure 2 Optical micrographs taken during the in situ thermal annealing at 25 oC, 60 o

C, 80 oC, and 100 oC. (a-d) CH3NH3PbI3 with tBP or (e-h) CH3NH3PbI3. Illustration

of the nucleation and growth of the grains (i) CH3NH3PbI3 with tBP or (j) CH3NH3PbI3 after annealing temperature (k) X-ray diffraction patterns of (XRD) of CH3NH3PbI3 with tBP or CH3NH3PbI3 fresh samples. To gain further insight into the effect of tBP treatment on the crystallization process, the in situ optical microscopy measurement was conducted.23 The measurement provided clear images in different stages of crystallization. we could observed both films were transparent at the room temperature (Figure 2a and 2e), when spin-coating the precursor on substrate. With it went up to 60 oC, several brown nucleis began to appear on the substrates (Figure 2b and 2f). However, the number of nucleis with tBP treatment were much less than that of without tBP treatment. It could be ascribed to the formation of intermediate phase which could suppress the nucleation of CH3NH3PbI3.24, 25 In order to confirm the existence of intermediate phase, the fresh samples were tested by XRD as depicted in Figure 2k. The fresh sample of CH3NH3PbI3 with tBP appeared many new peaks that could not be assigned to

reported

materials.29,

30

Thus

we

speculated

that a

new

compound

(CH3NH3I-PbI2-DMSO⋅tBPx) was formed. With the temperature increasing, the nucleis began to grow, as shown in the Figure 2c and 2g. On the last stage, the CH3NH3PbI3 crystal kept growing and formed continuous lagre-grain films at 100 oC (Figure 2d and 2h). However, these two images were quite different. The film with tBP treatment appeared the larger grain size. The mechanism of above process were depicted in Figure 2i and 2j.

6


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a

b 1.0

CH3NH 3PbI3

Normalized intensity (a.u.)

CH3NH3PbI3

CH3NH3PbI3 with tBP in precursor CH3NH3PbI3 with tBP in antisolvent

PL Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


700

750

800

850

CH3NH3PbI3 (tBP in precursor)

0.8

CH3NH3PbI3 (tBP in antisolvent)

0.6 0.4 0.2 0.0 80

100

Wavelength (nm)

120

140

160

180

200

220

Time (ns)

Figure 3 (a) The steady-state photoluminescence spectra. (b) Time resolved photoluminescence spectroscopy for the perovskite films on different substrates which were CH3NH3PbI3, CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3 with tBP in antisolvent. (c) Schematic diagram of CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3 with tBP in antisolvent. To gain the high efficiency perovskite solar cell devices, effective charge transport, long carrier lifetime and low charge recombination were needed. A high quality perovskite film and structure played a key role in low charge recombination. In order to prove CH3NH3PbI3 with tBP in antisolvent obtained higher quality and charge transfer than CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3. CH3NH3PbI3, CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3 with tBP in antisolvent were prepared on the cleaned glasses to prevent from the charge injection between perovskite layer and electron transfer layer. The PL peak intensities were found to increase upon addition of tBP, which signified the films with tBP treatment had a high quality. However, the different ways of adding of tBP additive also brought different influence on PL intensity. From Figure 3a, In comparison to the 7



sample of CH3NH3PbI3 with tBP in precursor, CH3NH3PbI3 with tBP in antisolvent presented a higher PL intensity. TR-PL decay curves of perovskite film based on CH3NH3PbI3, CH3NH3PbI3 with tBP in precursor and CH3NH3PbI3 with tBP in antisolvent were shown in Figure 3b. The CH3NH3PbI3 film was prepared on glass. From Figure 4b, the carrier lifetime of CH3NH3PbI3 with tBP in antisolvent was 28.27 ns. It was much longer than CH3NH3PbI3 (6.44 ns) and CH3NH3PbI3 with tBP in precursor (12.64 ns). As a result, carrier lifetime of CH3NH3PbI3 with tBP in antisolvent was greatly increased, which was coordinate with the PL spectra. The PL and TRPL of CH3NH3PbI3 with tBP treatment were improved by forming the high quality perovskite layer as previously described. In addition, inspired by the report of Han et al.,26 we proposed the method of tBP in antisolvent could induce the additives in perovskite to form a gradient structure (Figure 3c). Due to the gradient structure of additives distribution in CH3NH3PbI3, the tBP concentrations in perovskite were much less than tBP on the surface of the perovskite as depicted in Figure 3c. It greatly reduced the concentration of additive in the perovskite, thus decreased the tBP concentrations improved the electron diffusion in the perovskite. This speculation was also consistent with the above PL and TRPL results.

8


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b

80

20 60

IPCE (%)

-2 Current density (mA cm )

a 15

10

CH3NH3PbI3 with tBP CH3NH3PbI3


20

5

0 0.0

40

0.2

0.4

0.6

0.8

0 300

1.0

400

800

2

1

500

600

700

rse

3

20 15 10 5 0 0.0

800

Reverse

Foward

Jsc

21.39

21.35

mAcm

Voc

1.06

1.05

v

FF

0.77

0.73

PSC

17.41

16.42

0.2

Wavelength (nm)

0.4

rd

Absorbance (a.u)

700

ve Re


4

0 400

600

d

5

-2 Current density (mA cm )

c

500

Wavelength (nm)

Votage (v)

wa Fo

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


-2

%

0.6

0.8

1.0

Votage (v)

Figure 4 (a) The current density–voltage curves, (b) corresponding incident photon-to-current efficiency (IPCE) spectrum and (c) UV-vis absorption spectra devices of CH3NH3PbI3 and CH3NH3PbI3 with tBP treatment. (d) Current density– voltage curve of PSCs with different scanning directions. Both perovskite films above were fabricated into devices. The photovoltaic performance, corresponding incident photon-to-current efficiency (IPCE) spectrum and UV-vis absorption spectra were examined in Figure 4a ,4b and 4c. Figure 4a showed J-V curves of two devices, and the corresponding detailed device parameters were listed in Table S1. The champion PCE of 17.41% and 14.49% were achieved in CH3NH3PbI3 with tBP in antisolvent and CH3NH3PbI3 devices, respectively. As showed in Table S1, the device with tBP in antisolvent showed the higher short-current density mainly because of the enhanced grain size and charge transportation.27 The reason for high current was attributed to the formation of intermediate phase which will retard the crystallization of CH3NH3I and PbI2 to form a high quality film. Besides, the method of tBP in antisolvent might form a gradient structure (Figure 3c), greatly reduced the concentration of the additive in the perovskite, thus decreased the tBP concentrations improved the electron diffusion in the perovskite. It was also directly demonstrated by the increase in IPCE spectrum in Figure 4b. The FF exhibited an increase with the tBP treatment, indicating reduced 9



the defect and pinhole in perovskite layers.28 In addition, in Figure 4d, the hysteresis effect of the J-V curves was negligible.

d

CH3NH3PbI3 with tBP

Transmittance

c 15

PCE (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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10

1610

820

νC-C

νC-H

CH3NH3PbI3


5 0

5

10

15

20

25

4000

30

3500

3000

Time (days)

2500

2000

1500

Wavenumber (cm-1)

1000

500

-1

Figure 5 Contact-angle measurements of water droplet on the films of (a) CH3NH3PbI3 with tBP, (b) CH3NH3PbI3. (c) Devices stability of perovskite solar cells based on CH3NH3PbI3 thin films with or without tBP treatment. (d) Fourier transform infrared spectrometer (FTIR) of CH3NH3PbI3 with tBP or CH3NH3PbI3 after annealing temperature. The tBP was also employed as a surface modification agent to augment the hydrophobicity of CH3NH3PbI3. The FTIR spectroscopy showed two weak C-C and C-H bonds at 1610 and 820 cm−1 from tBP, suggesting that quite a bit part of tBP were still adsorbed in the CH3NH3PbI3 film which was used as hydrophobic protectant to improve the moisture resistance of PSCs in ambient air. Figure 5a and 5b showed contact-angle measurements of a water droplet on CH3NH3PbI3 with tBP or CH3NH3PbI3 film. The derived contact angles were 74.56°, and 53.26° for the CH3NH3PbI3 with or CH3NH3PbI3 film, respectively. It demonstrated that hydrophobicity of CH3NH3PbI3 film could be improved by adding tBP. In general, 10


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after CH3NH3PbI3 reacted with tBP, the hydrophobic tertiary butyl group surrounded on the outside. this was attribute to the strong coordination between the nitrogen atom on the end of tBP and the Pb2+ in CH3NH3PbI3. In addition, a device architecture with gradient structure was prepared by tBP in antisolvent. As shown in Figure 3c, the concentration on the surface of perovskite prepared by tBP in antisolvent was further greater than tBP in perovskite precursor. Therefore, the method of tBP in antisolvent resulted in the high hydrophobicity of CH3NH3PbI3 films.29, 30 To further test the stability of CH3NH3PbI3 with tBP in antisolvent, the PSCs were prepared to examine the effect of using this treatment on the change of CH3NH3PbI3 film. About 5-10 individual cells were measured for each of device to check the statistics of devices performance. The devices stability of PSCs based on CH3NH3PbI3 with tBP in antisolvent or CH3NH3PbI3 were given in Figure 5c. As illustrated in the Figure 5c, devices without tBP treatment showed rapidly deteriorating with PCE dropping to 6.9% after 5 days and 23.4% after 30 days. In comparison, devices with tBP treatment exhibited slower deterioration rate with the PCE keeping over 89% after 30 days.

4. CONCLUSION In summary, we formed a high quality CH3NH3PbI3 film through the addition of tBP in antisolvent. To further proved the impact of tBP treatment on crystallization process, the in situ optical microscopy, XRD were used to prove that tBP significantly suppressed

the

perovskite

nucleation

by

forming

the

intermediate

phase-CH3NH3I-PbI2-DMSO⋅tBPx. Besides, steady-state PL and TRPL showed that the method of tBP in antisolvent could achieve higher quality and charge transfer films than tBP in precursor solution and the pure perovskite. The derived contact angles demonstrated that hydrophobicity of the perovskite could be easily increased by incorporation of tBP. At last, a champion power conversion efficiency of 17.41% was developed via tBP treatment and the high efficiency device could maintain over 89% of the initial PCE after 30 days at room temperature with tBP treatment.

ACKNOWLEDGMENTS This work was supported by the National Basic Research Program of China under Grant No. 2016YFA0202400, 2015CB932200, the National Natural Science Foundation of China under Grant No. 21403247, the Distinguished Youth Foundation

11



of Anhui Province (1708085J09), and the Major/Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2016FXZY003).

ASSOCIATED CONTENT Supporting Information. A table of current density–voltage curves of PSCs, SEM images of perovskite films. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Phone: +86 1061772268 Notes The authors declare no competing financial interest.

REFERENCES (1) Hodes, G. Perovskite-Based Solar Cells. Science 2013, 342, 317-318. (2) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050-6051. (3) Bi, D.; Gao, P.; Scopelliti, R.; Oveisi, E.; Luo, J.; Grätzel, M.; Hagfeldt, A.; Nazeeruddin, M. K. High-performance Perovskite Solar Cells with Enhanced Environmental Stability Based on Amphiphile-modified CH3NH3PbI3. Adv. Mater. 2016, 28, 2910-2915. (4) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. I. Solvent Engineering for High-performance Inorganic-organic Hybrid Perovskite Solar Cells. Nat. Energy 2014, 13, 897-903. (5) Yang, Z.; Chueh, C. C.; Zuo, F.; Kim, J. H.; Liang, P. W.; Jen, A. K. Y. High-Performance Fully Printable Perovskite Solar Cells via Blade-coating Technique under the Ambient Condition. Adv. Energy Mater. 2015, 5, 1500328. (6) Noh, J. H.; Sang, H. I.; Jin, H. H.; Mandal, T. N.; Sang, I. S. Chemical Management for Colorful, Efficient, and Stable Inorganic-organic Hybrid Nanostructured Solar Cells. Nano Lett. 2013, 13, 1764-1769. (7) Eperon, G. E. Formamidinium Lead Trihalide: A Broadly Tunable Perovskite for Efficient Planar Heterojunction Solar Cells. Energy Environ. Sci. 2014, 7, 982-988. (8) Huang, F.; Dkhissi, Y.; Huang, W.; Xiao, M.; Benesperi, I.; Rubanov, S.; Zhu, Y.; Lin, X.; Jiang, L.; Zhou, Y. Gas-assisted Preparation of Lead Iodide Perovskite Films 12


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Incorporating 4-tert-Butylpyridine in an Antisolvent: A Facile Approach

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