Solution-processed perovskite solar cells using environmentally friendly solvent system

Solution-processed perovskite solar cells using environmentally friendly solvent system

Accepted Manuscript Solution-processed perovskite solar cells using environmentally friendly solvent system Yue Feng, Ke-Jian Jiang, Jin-Hua Huang, H...

833KB Sizes 8 Downloads 32 Views

Accepted Manuscript Solution-processed perovskite solar cells using environmentally friendly solvent system

Yue Feng, Ke-Jian Jiang, Jin-Hua Huang, Hui-Jia Wang, MingGong Chen, Yu Zhang, Li Zheng, Yan-Lin Song PII: DOI: Reference:

S0040-6090(17)30514-X doi: 10.1016/j.tsf.2017.07.019 TSF 36085

To appear in:

Thin Solid Films

Received date: Revised date: Accepted date:

28 February 2017 4 July 2017 8 July 2017

Please cite this article as: Yue Feng, Ke-Jian Jiang, Jin-Hua Huang, Hui-Jia Wang, MingGong Chen, Yu Zhang, Li Zheng, Yan-Lin Song , Solution-processed perovskite solar cells using environmentally friendly solvent system, Thin Solid Films (2017), doi: 10.1016/ j.tsf.2017.07.019

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 Solution-Processed Perovskite Solar Cells Using Environmentally Friendly Solvent System Yue Feng,a,b Ke-Jian Jiang,b* Jin-Hua Huang,b Hui-Jia Wang,b Ming-Gong Chen,a* Yu Zhang,b Li Zhengb and Yan-Lin Songb*

PT

a. School of Chemical Engineering of Anhui University of Science and Technology, Huainan, P.R. China, 232001.

RI

b. Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences,

*Corresponding

authors:

SC

Beijing, P.R. China, 100190.

[email protected];

NU

[email protected];

[email protected];

MA

Keyword: Non-toxic solvents; Solution deposition; Perovskites; Solar cells

D

Abstract:

PT E

Hybrid inorganic-organic perovskite solar cells have attracted great attention with power conversion efficiencies exceeding 20% using dimethylformamide or dimethyl sulfoxide for the deposition of the perovskite films. Replacing the toxic solvents with

CE

non-toxic solvents is one of the key challenges to realize industrial scale commercialization for the perovskite photovoltaics. Here, environmentally friendly

AC

solvent systems are employed for processing the perovskite active layer by a two-step spin-coating approach: aqueous Pb(NO3)2 is first spin-coated on mesoporous TiO2 film, and followed by spin-coating of methylammonium iodide in isopropanol. We found that the resulting perovskite was homogeneously covered on the TiO2 surface with relatively high coverage. The best performing perovskite solar cell shows a power conversion efficiency of 13.7% under standard conditions (AM1.5, 100 mW cm-2).

ACCEPTED MANUSCRIPT 1. Introduction Evolving from the dye-sensitized solar cells, organic-inorganic hybrid perovskite (typically, CH3NH3PbX3 (X = Cl, Br and I) solar cells have emerged as most promising photovoltaic technology due to their low cost, high light absorption capability, superior electron/hole mobility and facile solution processibility [1-5].

PT

Since the first reported perovskite-based solar cells using liquid electrolyte with 3.9% power conversion efficiency (PCE) by Kojima et al. in 2009 [1], tremendous efforts

RI

have been made in the following years. In 2012, Park et.al first reported solid-state perovskite solar cells with a PCE of 9.7% using spiro-OMeTAD as hole transport

SC

material [2]. With the development of fabrication methods for the perovskite active layer, such as vacuum evaporation [3], sequential deposition [4] , solvent engineering

NU

[6], vapor-assisted deposition [7], and additive-assisted deposition [8], high-quality films of MAPbI3 with flat surfaces and complete surface coverage have been obtained

MA

by controlling its rapid crystallization behavior, where PbI2 was usually employed in combination with MAI as the perovskite precursors.

D

On the other hand, in our previous reports, we observed that electrodeposited PbO

PT E

could be converted into CH3NH3PbI3 through reaction with MAI [9-10]. Recently, non-halide lead precursors such as lead chloride [11], lead acetate [12], and lead nitrate [13-14], are also known to be appropriate candidates for the synthesis of these

CE

materials. With these lead salts, CH3NH3+ rich environment were created, and thus slowed down the perovskite formation process and improve the growth of the crystal

AC

domains during annealing. In addition, these excess methyl ammonium non-halide salts could be released at a relatively low annealing temperature [12]. By now, for solution-processed perovskite solar cells using one-step or two-step deposition method, aprotic solvents, such as dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), were extensively employed to dissolve the perovskite precursors due to their coordination action to form intermediates such as PbI2-DMSO or CH3NH3I-PbI2-DMSO [15-17]. These solvents, however, are toxic to handle. In addition, these solvents have high boiling points, and the resulting films should be processed at relatively high temperature. Replacing toxic solvents with nonhazardous

ACCEPTED MANUSCRIPT solvents is thought to be one of the key challenges for industrial scale commercialization of thin film perovskite photovoltaics [18]. Recently, Shahverdi’s group reported a spray coating method for the fabrication of the perovskite layer, where the perovskite particles were dispersed in 2-propanol for the deposition [19]. The power conversion efficiencies, however, were limited between 9.07% and 7.71%,

PT

mainly due to poor coverage of the perovskite on substrate using this method. Very recently, Hsieh et. al. used H2O-propanol system for the deposition of the perovskite

RI

[13]. In the work, Pb(NO3)2 was first dissolved in water, and spin-coated on nanoporous TiO2 films, and followed by dipping in methylammonium iodide (MAI)

SC

solution in propanol for the perovskite conversion. In the dipping process, Pb(NO3)2 was first reacted with MAI to form PbI2, which further reacted with MAI to form

NU

MAPbI3. This process usually take a long time (~700 s) to ensure complete conversion from Pb(NO3)2 to MAPbI3, resulting in relatively poor coverage on TiO2

MA

film. The optimally performing device showed efficiency of 12.58%, and no average data was given. Considering of the issues, two-step spin-coating method is developed

D

for the deposition of the perovskite MAPbI3 on mesoporous TiO2 films using

PT E

environmentally friendly solvent systems.

2. Experimental section

CE

2.1 Fabrication of TiO2 film

Fluorine doped tin oxide (FTO) coated glass substrates (Nippon Sheet Glass Co.,

AC

Ltd. ~15Ω sq-1 resistance) were etched with zinc powder and HCl (2 M) and cleaned with soap (Hellmanex) and rinsed with Milli-Q water and ethanol, respectively. Then, the sheets were sonicated for 15 minutes in a solution of acetone: isopropanol (1:1 v/v), rinsed with ethanol and dried with compressed N2. After that, a UV/ozone treatment was performed for 15 minutes. Then, a 60 nm thick TiO2 blocking layer was deposited onto the substrates as follows: spin coating 0.15 M titanium (diisopropoxide) bis(2,4-pentanedionate) dissolved in n-butanol, and sintering at 500 oC for 30 min, then spin coating the same solution with 0.3 M and sintering under the same condition. After cooling down to room temperature, a 400 nm thick mesoporous TiO2 layer was

ACCEPTED MANUSCRIPT spin coated at 5,000 r.p.m for 30 s using commercial TiO2 paste diluted in ethanol at weight ratio 2:7, followed by annealing at 125 oC for 30 min and then heated at 500 o

C for 30 min. Finally, the cooled film was immersed in 0.02 M aqueous TiCl 4

solution at room temperature for 40 min. After rinsing with DI water and drying, the film was heated at 450 oC for 30 min.

PT

2.2 Fabrication of MAPbI3 film Two-step spin coating process was employed for the deposition of MAPbI3 on the

RI

mesoporous TiO2 film. First, Pb(NO3)2 was dissolved in water at 70℃with 1M concentration in combination with 1 wt % surfynol465 (surface active agent from Air

SC

Products). Then the solution was spin-coated on the mesoporous TiO2 film at 6000rpm for 10s. The Pb(NO3)2 aqueous solution was maintained at 70℃ and stirred

NU

during the entire spin-coating process. The water was removed by drying the spin-coated Pb(NO3)2 film at 70℃ for 30minutes. Subsequently, 20 mg/ml CH3NH3I

MA

solution in isopropanol was dropped on top of the Pb(NO3)2 film and kept for 20 s, followed by spin-coating at 3,000 r.p.m. for 20 s. This procedure was repeated three

D

times to guarantee a complete conversion of Pb(NO3)2 into perovskite. The resulting

PT E

perovskite film was rinsed with pure isopropanol and annealed at 85 ℃ in air for 10 min. Spin-coated on the Pb(NO3)2-coated TiO2 film. After the deposition, the samples were transferred to a nitrogen-filled glovebox (<1 ppm O2 and H2O). The hole layer

was

CE

transport

prepared

by

spin-coating

a

spiro-MeOTAD

(2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene)

solution

at

AC

4000 rpm for 30 s. The spin-coating formulation was prepared as follows: to 1 ml of chlorobenzene were added 75 mg of spiro-MeOTAD, 30 ml of 4-tert-butylpyridine, and 20 ml of a stock solution of 500 mg ml-1 Li-TFSI in acetonitrile. Finally, An 60 nm thick Au was thermally evaporated as a back contact under a vacuum of 3×10-5Torr. The device active area was 4 mm2, determined by the overlap of the cathode and anode. 2.3 Characterizations XRD patterns were recorded by using an X-ray diffractometer (Rigaku, D/MAX RINT-2500) with a CuK radiation source. The surface morphology of the films as

ACCEPTED MANUSCRIPT well as cross-section was analyzed by using a JEM-7500F field-emission scanning electron microscope (SEM). Absorption spectra of the film samples were recorded by using a Shimadzu UV/vis 1800 spectrophotometer. Current–voltage characteristics were recorded by applying an external potential bias to the cell while recording the generated photocurrent with a Keithley model 2400 digital source meter. The light source was a 300 W collimated xenon lamp (Newport) calibrated with the light

PT

intensity to 100 mW cm-2 under AM 1.5G solar light conditions by a certified silicon

RI

solar cell. The J–V curve was recorded by the reverse scans with a rate of 200 mV s-1. The external quantum efficiency (EQE) for solar cells was performed using a

SC

commercial setup (PV-25 DYE, JASCO). A 300 W Xenon lamp was employed as a

NU

light source for the generation of a monochromatic beam.

3. Results and discussion

MA

Scheme 1 illustrates the formation of the perovskite CH3NH3PbI3 on a mesoporous TiO2 (m-TiO2) substrate by two-step sequential deposition method. At first step,

D

Pb(NO3)2 as lead source was first deposited on TiO2 film from its aqueous solution.

PT E

Different from PbI2 or other non-halagen lead salts spin-coated from DMF solutions, aqueous Pb(NO3)2 has poor wettability on TiO2 film due to high surface tension coefficient of water (measured above 5.610-2 N·m-1). In the previous report,

CE

UV-ozone pretreatment on mesoporous TiO2 film was carried out to enhance wettability for hydrophilic Pb(NO3)2 before the spin-coating. Here, surfynol465 was

AC

used as surface active agent to improve the wettability [20]. With the addition of surfynol465 (0.5 wt%), the surface tension was significantly decreased from 5.610-2 N·m-1to 2.610-2 N·m-1. As shown in Fig. 1b and 1c, the deposited Pb(NO3)2 formed a well-connected and continuous island structure over the whole TiO 2 surface, although naked TiO2 film still remained. Without the addition, bulky Pb(NO3)2 crystallites were aggregated and distributed in isolation on TiO2 surface with poor coverage (Fig.1a). The result clearly indicated that small amount of the surface active agent could significantly improve the wettability of the aqueous Pb(NO3)2 solution on the TiO2 surface, which is required to obtain quality perovskite film with high

ACCEPTED MANUSCRIPT coverage for the efficient solar cells. A similar result was obtained through treatment of TiO2 surface using UV-ozone irradiation before spin-coating [13]. Still, the surface coverage is not complete, probably due to strong crystallinity from the aqueous solution. For conventional two-step spin-coating method for preparation of MAPbI3, PbI2 is

PT

usually spin-coated from the solution in DMF, and converted into the perovskite through reaction with methylammonium iodide. In that case, dark brown MAPbI3 film

RI

could form as soon as MAI is coated on PbI2 film. In contrast, replacing PbI2 with Pb(NO3)2, we observed that the formation of MAPbI3 was much slower as compared

SC

with that using PbI2. X-ray diffraction patterns were recorded for the conversion of Pb(NO3)2 with various coating numbers of MAI solution. As shown in Fig. 2a, after

NU

the first coating, characteristic diffraction peaks of pristine Pb(NO3)2 disappeared, and new peaks appeared at 12.9, 25.6, 38.9, and 53.2°, corresponding to the (001), (002),

MA

(003) and (004) lattice planes of the 2H polytype PbI2 (hexagonal structure). After the second coating, new diffraction peaks appeared at 2 = 14.2, 20.1, 28.5, 31.9 and

D

40.7°, assigned to the (110), (112), (220), (310), and (224) planes of the tetragonal

PT E

perovskite CH3NH3PbI3, while the diffraction peak at 2 = 12.7° for PbI2 decreased in intensity. After the third coating, the peaks for PbI2 completely disappeared, while the remained peaks for CH3NH3PbI3 became much stronger. According to the XRD

CE

diagram of the perovskite, the FWHM value of the (110) peak is 0.385°, corresponding to the crystallite size of about 21 nm evaluated from the Scherrer

AC

equation. The value is comparable with the value (0.401°) for the perovskite prepared by the conventional two-step solution method, indicating that both the perovskites have similar mean sizes of the perovskite crystallites [21]. For further investigation of the evolution, UV-vis absorption spectra were recorded. As shown in Fig. 2b, Pb(NO3)2 film has no absorption in the visible region. After the first coating of MAI solution, a typical absorption peak at 500 nm for PbI2 was observed. Upon the second coating, the spectrum was dramatically red shifted, indicative of the formation of the perovskite, while PbI2 still remained with a shoulder peak at 500 nm. After the third coating, a complete conversion was observed without

ACCEPTED MANUSCRIPT the shoulder peak for PbI2. From both the evolution of the UV-vis absorption and XRD spectra, we observed that the complete conversion of Pb(NO3)2 into CH3NH3PbI3 needed three times dropping of the CH3NH3I solution on top of the Pb(NO3)2 layer. The same result was reported that three times are required for drop coating of the CH3NH3I solution to guarantee a complete conversion of the perovskite

PT

when Pb(SCN)2 was used as lead source [22,23]. With further drop casting of the solution, we observed that the quality of the film became poorer with lower coverage.

RI

In previous report, Pb(NO3)2 film was dipped in MAI solution, and complete conversion was found to be more than 700 s [13]. In addition, it was reported that

SC

dropwise addition of a concentrated aqueous solution of Pb(NO3)2 to an aqueous solution containing large amount of CH3NH3I, a black precipitate of CH3NH3PbI3

NU

formed when the addition is carried out above ca. 40°C while a pale yellow crystalline solid (CH3NH3)4PbI6·2H2O with the solutions below 40°C [24]. In our experiments,

MA

the phenomenon was not observed, potentially due to the different condition employed. Different from the situation using PbI2 as lead source, where MAPbI3 (MA,

D

CH3NH3+ )could form quickly after spin coating by or dipping in MAI solution, the

PT E

formation of MAPbI3 from non-halide lead Pb(NO3)2 involves a two-step reaction (Scheme 2):

In the above reactions, MANO3 was produced as a by-product, and could be

CE

removed after washing from the film with propanol and further thermal annealing at 100 °C for 20 min. As shown in Fig. 3, the initial decomposition temperature (defined

AC

by T at 95% weight) of CH3NH3NO3 is about 207 °C, about 40 degree lower compared with CH3NH3I (248 °C). As shown in Fig. 4, the resulting MAPbI3 was coated on TiO2 surface with a 400 nm-thick capping layer. The MAPbI3 layer comprised by cuboid crystals, which are homogeneously covered on TiO2 surface with size ranged from 100 nm to 500 nm. The result is different from that of the MAPbI3 layer prepared by dipping approach, where poor coverage of MAPbI3 was inevitable due to exceeded soaking time required for the conversion. Our experimental result demonstrates that the environmental friendly water-ethanol system could be suitable for solution deposition

ACCEPTED MANUSCRIPT of quality perovskite film using the two-step spin coating technique. We fabricated perovskite solar cells employing the perovskite film as light absorber. Fig. 5a shows the J–V curves for the best device measured with bias scanning at a rate of 400 mV/s and under simulated AM 1.5G (100mWcm-2) solar irradiation in air. The device exhibited high photovoltaic performance with a short-circuit current (JSC) of

PT

20.5 mA cm−2, an open-circuit voltage (VOC) of 1010 mV, and a fill factor (FF) of 0.67, and a power conversion efficiency (PCE) of 13.7%, when forward bias scanning was

RI

employed, while the scanning in opposite direction, a PCE of 12.3% was obtained with JSC=20.4 mAcm-2, VOC=0.98 V, and FF=0.61. The observed hysteresis behavior

SC

indicates low and non-balanced charge transfers in the device. It is well known that the hysteresis behavior is an important issue for the perovskite solar cells, which has

NU

been observed and reported in many kinds of perovskite solar cells. In our experiments, we further observed that decreasing the scanning rate from 400 to 100

MA

mV/s, the values of Voc and FF slightly increased at the expense of the decrease in Jsc, resulting in the slight decrease in PCEs from 13.7 to 12.8% and 12.3 to 12.0% for

D

reversed and forward scanning, respectively. With increasing scanning rate from 400

PT E

to 1000 mV/s, the opposite trend was observed, resulting in lower PCE values of 12.3% and 11.5% for reversed and forward scanning, respectively. Fig. 5b shows the incident photon-to-current conversion efficiency (IPCE) for the

CE

two-step spin coating device over the spectral range from 400 to 800 nm, the integration of the IPCE spectrum over the solar emission yields AM 1.5 photocurrent

AC

of 19.5 mA/cm2, in excellent agreement with the measured JSC values, indicating that the spectral mismatch between our simulator and the true AM 1.5 solar emission is small.

Further enhancement in PCE can be expected through improvement of the quality of the perovskite layer with large crystalline grains and high coverage [21-22]. The average PCE for 20 devices was 12.8±1.0% with JSC of 19.2±1.5 mA cm−2, VOC of 960±80 mV, and FF of 0.58±0.10 at the forward scanning condition. The detailed data are listed in Table 1. We also tried to prepare the perovskite active layer through dipping approach with the Pb(NO3)2/TiO2 film in various MAI solutions (10 mg/ml,

ACCEPTED MANUSCRIPT in isopropanol) with various duration, and found it was difficult to completely convert the Pb(NO3)2 into the perovskite, even immersion more than 20 minutes. Moreover, we observed that some of the perovskite layer was peeled off from the TiO2 film after the prolonged soaking (the data not shown here).

PT

4. Conclusion In this report, a two-step spin-coating method was successfully employed for

RI

deposition of the CH3NH3PbI3 perovskite film using environmentally friendly solvents (H2O and iso-propanol) to dissolve the perovskite precursors (Pb(NO3)2 and

SC

CH3NH3I). The resulting film was homogeneously covered on TiO2 surface with size ranged from 100 nm to 500 nm. With the perovskite absorber, mesoporous solar cell

NU

was fabricated, affording a best power conversion efficiency of 13.7% with average value of 12.8±1.0%. Our experimental result demonstrates that the two-step

MA

spin-coating method could be suitable for solution deposition of quality perovskite film for high-efficiency solar cells using the environmental friendly water-ethanol

Acknowledgements

PT E

D

system.

This work was supported by the 973 Program (Nos. 2013CB933004), the National

CE

Nature Science Foundation of China (Grant Nos. 61405207, 21174149, 51473173, 91433202 and 21221002), and the “Strategic Priority Research Program” of Chinese

AC

Academy of Sciences (Grant No. XDA09020000 and XDB12010200).

Notes and references [1] A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halide perovskites as visible-light sensitizers for photovoltaic cells, J. Am. Chem. Soc. 131 (2009) 6050-6051. [2] H.-S. Kim, C.-R. Lee, J.-H. Im, K.-B. Lee, T. Moehl, A. Marchioro, S.-J. Moon, R. Humphry-Baker, J.-H. Yum, J.-E. Moser, M. Grätzel, N.-G. Park, Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with

ACCEPTED MANUSCRIPT efficiency exceeding 9%, Sci. Rep. 2 (2012) 591. [3] M. Liu, M. B. Johnston, H.J. Snaith, Efficient planar heterojunction perovskite solar cells by vapour deposition , Nature 501 (2013) 395-398. [4] J. Burschka, N. Pellet, S.-J. Moon, R. Humphry-Baker, P. Gao, M.K. Nazeeruddin, M. Grätzel, Sequential deposition as a route to high-performance perovskite-sensitized

PT

solar cells, Nature 499 (2013) 316-319. [5] M. A. Green, A. Ho-Baillie, H. J. Snaith, The emergence of perovskite solar cells,

RI

Nat. Photonics 8 (2014) 506-514.

[6] Q. Chen, H. Zhou, Z. Hong, S. Luo, H.-S. Duan, H.-H. Wang, Y. Liu, G. Li, Y.

SC

Yang, Planar heterojunction perovskite solar cells via vapor-assisted solution process, J. Am. Chem. Soc. 136 (2014) 622-625.

NU

[7] M. Xiao, F. Huang, W. Huang, Y. Dkhissi, Y. Zhu, J. Etheridge, A. Gray-Weale, U. Bach, Y.-B. Cheng, L. Spiccia, A fast deposition-crystallization procedure for

MA

highly efficient leadiodide perovskite thin-film solar cells, Angew. Chem. Int. Ed. 53 (2014) 9898-9903.

D

[8] P.-W. Liang, C.-Y. Liao, C.-C. Chueh, F. Zuo, S.T. Williams, X.-K. Xin, J. Lin,

PT E

A.K.-Y. Jen, Additive enhanced crystallization of solution-processed perovskite for highly efficient planar-heterojunction solar cells, Adv. Mater. 26 (2014) 3748-3754.

CE

[9] X.-P. Cui, K.-J. Jiang, J.-H. Huang, X.-Q. Zhou, M.-J. Su, S.-G. Li, Q.-Q. Zhang, L.-M. Yang, Yan-Lin Song, Electrodeposition of PbO and its in situ conversion to

AC

CH3NH3PbI3 for mesoscopic perovskite solar cells, Chem. Commun. 51 (2015), 1457-1460.

[10] J.-H. Huang, K.-J. Jiang, X.-P. Cui, Q.-Q. Zhang, M. Gao, M.-J. Su, L.-M. Yang, Y. L. Song, Direct conversion of CH3NH3PbI3 from electrodeposited PbO for highly efficient planar perovskite solar cells, Sci. Rep. 5 (2015) 15889. [11] M.M. Lee, J. Teuscher, T. Miyasaka, T.N. Murakami, H. J. Snaith, Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites, Science 338 (2012) 643-647. [12] W. Zhang, M. Saliba, D.T. Moore, S.K. Pathak, M.T. Horantner, T. Stergiopoulos,

ACCEPTED MANUSCRIPT S.D. Stranks, 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, Ultrasmooth organic–inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells, Nat. Commun., 6 (2014) 6142. [13] T.-Y. Hsieh, T.-C. Wei, K.-L. Wu, M. Ikegami, T. Miyasaka, Efficient perovskite

PT

solar cells fabricated using an aqueous lead nitrate precursor, Chem. Commun. 51(2015) 13294-13297.

RI

[14] F.K. Aldibaja, L. Badia, E. Mas-Marza, R.S. Sanchez, E.M. Barea, I. Mora-Sero, Effect of different lead precursors on perovskite solar cell performance and

SC

stability, J. Mater. Chem. A 3 (2015) 9194-9200.

[15] W.S. Yang, J.H. Noh, N.J. Jeon, Y.C. Kim, S. Ryu, J. Seo, S. II. Seok,

intramolecular

photovoltaic

exchange,

perovskite

NU

High-performance

Science

(6240)

fabricated (2015)

through

1234-1237.

MA

(DOI:10.1126/science.aaa9272).

348

layers

[16] W. Li, J. Fan, J. Li, Y. Mai, L. Wang, Controllable grain morphology of

D

perovskite absorber film by molecular self-assembly toward efficient solar cell

PT E

exceeding 17%, J. Am. Chem. Soc. 137 (2015) 10399-10405. [17] N. Ahn, D.-Y. Son, I.-H. Jang, S.M. Kang, M. Choi, N.-G. Park, Highly reproducible perovskite solar cells with average efficiency of 18.3% and best

CE

efficiency of 19.7% fabricated via Lewis base adduct of lead(II) iodide, J. Am. Chem. Soc. 137 (2015) 8696-8699.

AC

[18] K.L. Gardner, J.G. Tait, T. Merckx, W. Qiu, U.W. Paetzold, L. Kootstra, M. Jaysankar, R. Gehlhaar, D. Cheyns, P. Heremans, J. Poortmans, Nonhazardous solvent systems for processing perovskite photovoltaics, Adv. Energy Mater. 6 (2016) 1600386. [19] B.A. Nejand, S. Gharibzadeh, V. Ahmadi, H.R. Shahverdi, Novel Solvent-free Perovskite Deposition in Fabrication of Normal and Inverted Architectures of Perovskite Solar Cells, Sci. Rep. 6 (2016) 33649. [20] J. Wang, J. Jin, Y. Tan, Z. Shi, S. Zhang, Kinetics of a hydrolysis reaction in critical surfynol465/n-butanol/ethyl acetate/water microemulsion, J. Mol. Liq.

ACCEPTED MANUSCRIPT 218 (2016) 128-132. [21] N. Adhikari, A. Dubey, E.A. Gaml, B. Vaagensmith, K.M. Reza, S.A.A. Mabrouk, S. Gu, J. Zai, X. Qian, Q. Qiao, Crystallization of a perovskite film for higher performance solar cells by controlling water concentration in methyl ammonium iodide precursor solution, Nanoscale 8 (2016) 2693–2703.

PT

[22] 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, A.D. Mohite,

RI

High-efficiency solution-processed perovskite solar cells with millimeter-scale grains, Science 347 (2015) 522.

SC

[23] X. Li, D. Bi, C. Yi, J.-D. Décoppet, J. Luo, S.M. Zakeeruddin, A. Hagfeldt, M. Grätzel, A vacuum flash–assisted solution process for high-efficiency large-area solar

cells,

Science

(DOI:10.1126/science.aaf806).

353

NU

perovskite

(6294)

(2016)

58-62

MA

[24] B.R. Vincent, K.N. Robertson, T.S. Cameron, O. Knop, Alkylammonium lead halides. Part 1. Isolated PbI64− ions in (CH3NH3)4PbI6•2H2O, Can. J. Chem. 65

AC

CE

PT E

D

(1987) 1042-1046.

ACCEPTED MANUSCRIPT

PT

ToC:

Scheme 1 Schematic illustration for deposition of the perovskite CH3NH3PbI3 on

RI

mesoporous TiO2/FTO substrate by two-step spin-coating process.

SC

Scheme 2. The mechanism to form perovskite from Pb(NO3)2 and CH3NH3I.

NU

Figure 1 (a) SEM surface images of Pb(NO3)2 film on mesoporous TiO2 surface, prepared from aqueous Pb(NO3)2 solution (a) without the addition of surfynol465, (b)

MA

with the addition of 0.5 wt% surfynol465, and (c) high magnification of (b).

D

Figure 2 XRD patterns (a) and UV-vis absorption spectra (b) for the Pb(NO3)2 films

PT E

treated with various coating numbers of MAI solution.

Figure 3 Thermal gravimetric analysis (TGA) curves for CH3NH3X (X=NO3 and I) in

CE

nitrogen atmosphere.

AC

Figure 4 SEM top (a) and cross-sectional (b) images of perovskite film prepared by two-step spin-coating method.

Figure 5 (a) J-V curves for the best cell using two-step spin-coating method recorded in reverse and forward scanning directions. (b) IPCE curve and integrated current for the best cell.

Table 1 Photovoltaic properties of the CH3NH3PbI3 perovskite solar cells formed from Pb(NO3)2 using water-iso-propanol solvent system.

PT

ACCEPTED MANUSCRIPT

RI

Scheme 1 Schematic illustration for deposition of the perovskite CH3NH3PbI3 on

NU

SC

mesoporous TiO2/FTO substrate by two-step spin-coating process.

AC

CE

PT E

D

MA

Scheme 2. The mechanism to form perovskite from Pb(NO3)2 and CH3NH3I.

CE

PT E

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

AC

Figure 1 (a) SEM surface images of Pb(NO3)2 film on mesoporous TiO2 surface, prepared from aqueous Pb(NO3)2 solution (a) without the addition of surfynol465, (b) with the addition of 0.5 wt% surfynol465, and (c) high magnification of (b).

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

Figure 2 XRD patterns (a) and UV-vis absorption spectra (b) for the Pb(NO3)2 films

AC

CE

PT E

D

treated with various coating numbers of MAI solution.

PT

ACCEPTED MANUSCRIPT

RI

Figure 3 Thermal gravimetric analysis (TGA) curves for CH3NH3X (X=NO3 and I) in

AC

CE

PT E

D

MA

NU

SC

nitrogen atmosphere.

D

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

PT E

Figure 4 SEM top (a) and cross-sectional (b) images of perovskite film prepared by

AC

CE

two-step spin-coating method.

MA

NU

SC

RI

PT

ACCEPTED MANUSCRIPT

D

Figure 5 (a) J-V curves for the best cell using two-step spin-coating method recorded

PT E

in reverse and forward scanning directions. (b) IPCE curve and integrated current for the best cell.

CE

Table 1 Photovoltaic properties of the CH3NH3PbI3 perovskite solar cells formed from Pb(NO3)2 using water-iso-propanol solvent system. Voc (mV)

FF (%)

PCE (%)

Device-rev

20.5

1010

67

13.7

Device-for

20.4

980

61

12.3

Device-av

19.2 ± 1.5

960 ± 80

58 ± 10

12.8 ± 1.0

AC

Jsc (mA cm-2)

sample

Notes: “rev” and “for” denote reverse and forward for bias scanning direction of the devices, respectively. The data for Device-av are the average of 20 samples.

ACCEPTED MANUSCRIPT

AC

CE

PT E

D

MA

NU

SC

RI

PT

HIGHLIGHTS:  Solution-processable perovskite film  environmentally friendly solvent system for solution deposition  perovskite film with high coverage and crystalline