Slot-Die Coated Perovskite Films Using Mixed Lead Precursors for

Subscriber access provided by UNIV OF DURHAM

Applications of Polymer, Composite, and Coating Materials

Slot-die coated perovskite films using mixed lead precursors for highly reproducible and large-area solar cells Donmin Lee, Yen-Sook Jung, Youn-Jung Heo, Sehyun Lee, Kyeongil Hwang, Ye-jin Jeon, Jueng-Eun Kim, Jiyoon Park, Gun Young Jung, and Dong-Yu Kim ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b02549 • Publication Date (Web): 18 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27 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

ACS Applied Materials & Interfaces

Slot-die coated perovskite films using mixed lead precursors for highly reproducible and large-area solar cells Donmin Lee,†,‡ Yen-Sook Jung,§ Youn-Jung Heo,†,‡ Sehyun Lee,†,‡ Kyeongil Hwang,†,‡ Ye-Jin Jeon,†,‡ Jueng-Eun Kim,†,‡ Jiyoon Park,‡ Gun Young Jung‡ and Dong-Yu Kim *,†,‡ †

Research Institute for Solar and Sustainable Energies (RISE), Heeger Center for Advanced

Materias (HCAM), Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagiro, Buk-gu, Gwangju 61005, Republic of Korea.

KEYWORDS: slot-die coating, perovskite solar cells, gas-blowing process, scalable printing process, mixed lead precursors

ABSTRACT

Recently, many kinds of printing processes have been studied to fabricate perovskite solar cells (PeSCs) for mass production. Among them, slot-die coating is a promising candidate for roll-toroll processing because of high-throughput, easy module patterning, and a pre-metered coating

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 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

Page 2 of 27

system. In this work, we employed mixed lead precursors consisting of PbAc2 and PbCl2 to fabricate PeSCs via slot-die coating. We observed that slot-die-coated perovskite films based on the mixed lead precursors exhibited well-grown and uniform morphology, which was hard to achieve by using only a single lead source. Consequently, PeSCs made with this precursor system showed improved device performance and reproducibility over single PbAc2. Lastly, a large-area module with an active area of 10 cm2 was fabricated with a power conversion efficiency of 8.3%.

INTRODUCTION Organic-inorganic lead halide perovskites have been attracting great attraction as promising photovoltaic materials due to a number of advantages such as a high absorption coefficient,1 tunable bandgap,2 a long carrier diffusion length3 and solution processability.4 By the benefit of these unique and attractive properties, perovskite materials have been successfully introduced as the light absorbing active layer in thin film solar cells and have enabled many researchers to fabricate high performance devices with a rapid growth of power conversion efficiency (PCE) from 3.8%5 to 22.1%6 in a short period of time. Perovskite film morphology has a great effect on device performance, where large crystal size and uniform and pinhole-free morphology are generally required for high performance of PeSCs. For this reason, many approaches have been developed to effectively control perovskite film morphology, such as anti-solvent dripping,7,8 solvent vapor annealing,9 introduction of additives, and various lead precursor selection,10,11 and device performance has steadily increased.


2

Page 3 of 27 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


However, most PeSCs with high efficiency have been predominantly demonstrated through non-scalable spin coating. Although spin coating is the most common technique to prepare uniform and reproducible thin films, it is difficult to make roll-to-roll compatible. Therefore, device fabrication through a scalable printing process, which enables high throughput and mass production, is regarded as the next step toward commercialization of PeSCs. Some research groups have successfully demonstrated the PeSCs using various printing techniques such as spray casting,12 doctor blade coating,13,14 inkjet printing,15–17 slot-die coating18,19 and meniscusassisted solution printing (MASP)20 which could be easily translated to roll-to-roll processing. However, studies on printing-based PeSCs are still at a minor level compared to those on spin coating based PeSCs. A method that has been proven in spin coating must be adequately modified for the printing process due to distinctively different film forming mechanisms between two processes. Furthermore, it is especially important to increase the reproducibility of the device in ambient conditions since the printing process proceeds mainly in air rather than a wellcontrolled glove box. Therefore, various attempts based on spin coating should be carefully reexamined to verify those methods are really effective for the printing process. In the spin-coating process, some research groups have successfully replaced the conventional PbI2 with other lead sources such as lead chloride (PbCl2), nitrate (Pb(NO3)2), and acetate (PbAc2).10,11 They confirmed that different types of lead precursor influenced the crystal growth kinetics, which changed the final perovskite film morphology and properties. PbCl2 has been reported to generate the CH3NH3PbI3-xClx perovskite and improved the crystal formation, although the role of Cl is still controversial.21 Especially, these mixed lead halide perovskites had charge carrier diffusion lengths exceeding 1 µm with a long recombination lifetime.1 Although they had improved film morphology and crystallinity with enlarged grains,22 the fabrication of


3


Page 4 of 27

PeSCs with PbCl2 usually requires time-consuming post-treatment of the perovskite film of more than 1 hour.23 Along with conventional lead halide materials, non-halide lead sources have also been employed as potential candidates for perovskite precursor materials. Miyasaka et al. reported a novel aqueous Pb(NO3)2 precursor based PeSCs with 12.58% PCE,24 but the Pb(NO3)2containing system showed poor film morphology due to spherulitic crystal growth.22 The other non-halide lead source, PbAc2, induced fast crystallization due to the facile removal of a thermally unstable organic by-product, MAAc, which resulted in relatively smooth and pinhole less perovskite morphology.26 These properties of PbAc2 would be beneficial to induce fast crystallization in scalable printing processes which do not have self-quenching processing like spin coating. However, fast crystallization of PbAc2 causes perovskite films to have small size of crystals which could limit the performance of solar cells.22 To overcome this problem, a new precursor system based on PbAc2 and PbCl2 was demonstrated for solar module via spin coating method.27 Herein, we demonstrated the deposition of perovskite active layer via slot-die coating in ambient conditions by using mixed lead precursors consisting of PbAc2 and PbCl2, which overcame the difficulties with a single lead precursor. PbAc2 is helpful in depositing a fully covered perovskite film by fast crystallization and a small amount of PbCl2 improves the grain size and morphology of the film. In addition, these mixed lead precursors were able to reduce the long post-treatment time of PbCl2 effectively. Thus, mixed lead precursors had a great synergistic effect on fabricating high quality PeSCs rather than using only one lead source, which could be easily applicable to the scalable process of slot-die coating. We compared PeSCs fabricated by using only PbAc2 and mixed lead precursors, and the device fabricated by the


4

Page 5 of 27 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


corresponding mixed lead precursors showed more uniform film morphology and improved device performance compared to only PbAc2. Moreover, we observed that mixed lead precursors showed superior reproducibility and stability than a single lead source. Finally, to confirm the scalability of these mixed lead precursors, we manufactured a large area module via slot-die coating and as a result, the PeSC module achieved a PCE of 8.3%.

RESULTS AND DISCUSSIONS The device structure used in this research is shown in Figure 1a. We fabricated an inverted structure of PeSC with a configuration of indium tin oxide (ITO) / poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) PEDOT:PSS / CH3NH3PbI3 / C60 / phenyl-C61butyric acid methyl ester (PCBM) / bathocuproine (BCP) / Ag. We were able to deposit all of the layers by low-cost solution processing except for the metal electrode.28,29 Perovskite solutions were prepared with a 3:1 molar ratio of CH3NH3I:PbX2 in N,N-Dimethylformamide, and PbX2 consisting of PbAc2 and PbCl2 with different ratios. The perovskite layer was fabricated under an ambient atmosphere via a scalable process of slot-die coating method, as shown in Figure 1b. We connected the N2 gas blower to the slot-die coater directly to give an additional quenching effect, as reported in previous work.18 Actually, various gas blowing approaches were also applied to spin coating method to fabricate highly uniform perovskite films by controlling the kinetics of nucleation and crystal growth.30,31 Afterwards, the films were instantly dried after deposition and we were able to obtain uniform and pinhole-free perovskite films.


5


Page 6 of 27

Figure 1. Schematic illustration of (a) the perovskite solar cells and (b) slot-die coating. To optimize blend ratios, we performed a scanning electron microscope (SEM) analysis on the surfaces of films with various PbAc2:PbCl2 molar ratios of 10:0, 8:2, 6:4, and 4:6. We excluded blend ratios with more PbCl2 because the time-consuming post-annealing processing of PbCl2 of over 1 hour was deemed incompatible with high throughput roll-to-roll processing.21,32 As shown in Figure 2a, the perovskite film made from only PbAc2 exhibited a pinhole-free and fully covered image, and this morphology was comparable to that of the spin-coating method reported by Zhang et al.26 However, it was composed of many small grains with sizes under 100 nm, which caused the high grain boundary density to play the role of charge trap sites and limited the device performance.33,34 To enlarge the grain size of the perovskite films, we incorporated PbCl2 in the precursor solution. The film fabricated with 8:2 mixed precursors showed larger sized


6

Page 7 of 27 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


grains in the range of 200 ~ 500 nm without loss of film uniformity and coverage, as shown in Figure 2b. However, further increasing the PbCl2 ratio in the precursor solutions resulted in large pinholes and deteriorated film images, which could have an undesirable influence on the device performance, as shown in Figure 2c and d.

Figure 2. Top-view SEM images of the slot-die coated perovskite films prepared with PbAc2 : PbCl2 ratios of (a) 10:0, (b) 8:2, (c) 6:4, and (d) 4:6. Device performance was well matched with the film morphology observed in the SEM analysis. The average photovoltaic parameters of each device with various blend ratios are summarized in Table 1. The champion cell fabricated with an 8:2 ratio of mixed lead precursors exhibited a device performance with an open-circuit voltage (VOC) of 0.89 V, a short-circuit current density (JSC) of 19.9 mA/cm2, a fill factor (FF) of 0.74, and a PCE (η) of 13.3% from J-V measurements (Figure S1a). The incident photon-to-current efficiency (IPCE) curve of the champion cell indicates that the measured JSC was consistent with the integrated photocurrent value of 19.3 mA/cm2 (Figure S1b). On the basis of the aforementioned results, we selected the


7


Page 8 of 27

8:2 ratio as the optimized condition of mixed lead precursors and compared it with the PbAc2only device.

Table 1. Average photovoltaic parameters of slot-die coated PeSCs with various mixed precursor ratios.

PbAc2:PbCl2

VOC (V)

JSC (mA/cm2)

FF (-)

PCE (%)

10:0

0.89 ± 0.04

13.8 ± 3.6

0.72 ± 0.09

8.9 ± 2.7

8:2

0.88 ± 0.04

16.6 ± 1.5

0.78 ± 0.03

11.4 ± 1.1

6:4

0.91 ± 0.01

13.5 ± 1.9

0.68 ± 0.05

8.3 ± 1.7

4:6

0.93 ± 0.02

6.9 ± 3.4

0.68 ± 0.02

4.5 ± 2.2

We were able to observe the greatly improved reproducibility in the device with mixed lead precursors over single PbAc2. Figure 3a shows the histogram of the obtained PCEs measured from devices with ratios of 10:0 and 8:2. The device fabricated with the 10:0 ratio had poor reproducibility and a very wide PCE distribution ranging from 3 to 11%, but the mixed precursors showed improved reproducibility with a narrow distribution. A similar tendency in device performances was also observed in the PCE deviation of individual cells on one substrate, as shown in Figure 3b. The inset image in Figure 3b shows that a device manufactured via slotdie coating had seven individual cells on the substrate. We numbered each cell from 1 to 7 and their PCEs were recorded individually on a graph. The device fabricated with PbAc2 only showed a very inconsistent distribution of efficiency on one substrate as shown in Figure 3b. On the other hand, the device with mixed lead precursors exhibited uniform and consistent PCE on one substrate.


8

Page 9 of 27 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


Figure 3. (a) A PCE histogram of PeSCs and (b) PCEs of seven different individual cells on one substrate fabricated with PbAc2 : PbCl2 ratios of 10:0 and 8:2. We were able to find the reason for significantly different uniformity and reproducibility between the single lead source and mixed lead precursors from the cross-sectional SEM images shown in Figure 4. From the previously observed surface morphology in Figure 2, we observed the pinhole-free and fully covered film image from both precursors with 10:0 and 8:2 ratios of PbAc2:PbCl2. However, in the cross-sectional SEM images, the film with the 10:0 ratio had large voids in the bottom side, as shown in Figure 4a. Such a nonuniform morphology caused the devices to have poor reproducibility and inconsistent device performance. On the other hand, the perovskite layer fabricated with the 8:2 ratio solution exhibited highly uniform morphology with well-grown grains across the entire thickness of perovskite layer, as shown in Figure 4d.


9


Page 10 of 27

To investigate the reason for the different film morphology depending on the precursor ratio, we carefully studied the cross-sectional film morphologies by separately controlling the gas blowing and thermal annealing processes. In the case of PbAc2-only precursor system, the film fabricated with the gas-blowing process only (Figure 4b) exhibited similar cross-sectional SEM image with that including both thermal annealing and gas-blowing processes (Figure 4a). The gas-blowing process accelerated the solidification of film surface due to the fast removal of volatile by-product, methylammonium acetate (MAAc),26 and the rapidly solidified surface would have blocked the evaporation of solvent and by-product. After that, trapped residual solvent and by-product escaped from the film and left large voids near the substrate. However, the film made without the gas-blowing process had compactly grown morphology without large voids as shown in Figure 4c. In this case, the perovskite crystallization seemed to occur dominantly from the bottom side of the film which is close to the heat source. Meanwhile, in the mixed lead precursors system, PbCl2 made less volatile by-product than PbAc2 and retarded the conversion of precursor solution. Therefore, solvent and by-product could be easily escaped from the film during and after the gas-blowing process and fully grown compact morphology was obtained as shown in Figure 4e. On the other hand, the film fabricated without the gas-blowing process exhibited uneven morphology with rough and bumpy surfaces as shown in Figure 4f. Although large voids were not observed in the film, nonuniform and undulating surface morphology caused the poor device performance (Figure S2). Thus, the gas-blowing process should be applied to the deposition of films to obtain the flat and uniform surface. However, for the fast evaporating precursor system such as PbAc2, the application of gas-blowing was not successful because surface could be too quickly solidified and leave voids inside as discussed earlier. At this point, the mixed lead precursor based system which had slightly retarded


10

Page 11 of 27 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


crystallization rate was more favorable to obtain well-controlled film morphology via gas-blower assisted coating method.

Figure 4. Cross-sectional SEM images of the perovskite films according to the composition of precursor materials fabricated with (a), (d) both gas blowing and thermal annealing, (b), (e) gas blowing only and (c), (f) thermal annealing only. (G.B.: gas-blowing process and T.A.: thermalannealing process.)

We propose a mechanism for the film deposition and crystallization for each precursor solution in a schematic illustration in Figure 5. The gas blower passed over the films immediately after deposition, and then conversion of precursor solutions predominantly occurred from the upper surface of films. Substrates were transferred onto a hotplate for thermal annealing to remove the residual solvent and by-products from the films, and further perovskite crystallization occurred during this process. In the case of film with only PbAc2, residual solvent and by-products were trapped under rapidly crystallized top crust and they have left large voids near the bottom side of film during thermal annealing process. It was confirmed by similar cross-sectional SEM images


11


Page 12 of 27

shown in Figure 4a and b that the gas-blowing process predominantly affected the crystallization of perovskite especially on the surface. On the other hand, PbCl2 made less volatile by-product than PbAc2 and retarded the crystallization of films, so the film deposited by the mixed lead precursors could release solvents and by-products effectively. Therefore, the mixed lead precursors consisting of PbAc2 and PbCl2 were able to make the crystals grow compactly and to fabricate uniform, flat and well-grown perovskite films. From these results, we propose that the gas-blowing process had a significant and beneficial influence on the surface morphology and final film formation. Moreover, under the gas-blowing condition, the composition of precursor solutions played an important role into the formation of well-controlled film morphology.

Figure 5. Schematic diagram of the perovskite film-formation mechanism via slot-die coating under the gas-blowing process.

Usually, grain boundaries and pinholes are known to play the role of trap sites for charge recombination in the perovskite layer.35 As discussed previously, the film fabricated with only PbAc2 had more trap sites such as large voids and grain boundaries contrary to the 8:2 ratio of


12

Page 13 of 27 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


the mixed lead precursors. Therefore, to validate that the difference in device performance between single PbAc2 and the mixed lead precursors related to such defects and trap sites, we investigated voltage dependence to light intensity and electrochemical impedance spectroscopy (EIS) measurements. The power law dependence of VOC on light intensity is shown in Figure 6a. In the power law dependence of VOC to light intensity, the slope of the graph indicated the trapassisted charge recombination relationship of the solar cells. The value of the slope became closer to kBT/q when the film had less charge trap sites such as pinholes and grain boundaries. The devices showed slopes of 2.38 kBT/q and 1.41 kBT/q for the 10:0 and 8:2 ratios of PbAc2:PbCl2. The device fabricated with 8:2 ratio had a slope value closer to kBT/q than that with 10:0 ratio, which means that there was less trap-assisted recombination in the device with the 8:2 ratio.36,37 EIS measurements also gave information about the charge transfer and recombination of the PeSCs.38 Figure 6b shows Nyquist plots of the EIS for the PeSCs with the 10:0 and 8:2 ratios of PbAc2:PbCl2. The semicircle at low-frequency was attributed to the charge recombination resistance (Rrec) of the photoactive layers.39 The device with the 8:2 ratio exhibited a larger radius of semicircle than the 10:0 ratio, which means that trap-assisted charge recombination was more suppressed in the device with mixed lead precursors. The resistance values obtained from the EIS measurements are summarized in Table S1.


13


Page 14 of 27

Figure 6. (a) Light intensity dependent VOC and (b) Nyquist plots of PeSCs fabricated with PbAc2:PbCl2 ratios of 10:0 and 8:2.

The stability of the solar cells fabricated with the 10:0 and 8:2 ratios was also evaluated in an ambient environment. Their PCE changes over time are graphed in Figure 7a. In the case of the device with the 10:0 ratio, its PCE dropped steeply to under 20% after 40 hours and reached zero after 100 hours. However, the device with the 8:2 ratio showed relatively improved stability with a slow drop in PCE until 100 hours. The 8:2 ratio film had larger sized grains, which means that there were less grain boundaries and pinholes than the film with the 10:0 ratio. Less grain boundaries are normally beneficial to long-term device stability because these defect sites usually act as the starting point of film degradation.40


14

Page 15 of 27 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


Finally, to validate the possibility of mixed lead precursors for device upscaling, we fabricated a large-area module via slot-die coating. The total active area was 10 cm2, which was interconnected with 4 individual sub-cells in series, as shown in the inset in Figure 7b. Utilizing the 3D printer-based slot-die coating system reported from our lab,18 we were able to successfully deposit the stripe-patterned perovskite film on a large-area substrate. The best module performance with a PCE of 8.3%, VOC of 3.8 V, JSC of 4.1 mA/cm2, and FF of 0.52 was obtained. From these results, these mixed lead precursor system has been confirmed to possess great potential in the manufacture of PeSCs via a well-controlled printing process.

Figure 7. (a) Normalized PCEs of PeSCs fabricated with PbAc2:PbCl2 ratios of 10:0 and 8:2 stored in ambient condition. (b) J-V curve of fabricated module with optimized mixed lead precursors.


15


Page 16 of 27

CONCLUSION In conclusion, we made highly reproducible PeSCs via slot-die coating using mixed lead precursors consisting of PbAc2 and PbCl2. These mixed lead precursors not only exhibited the advantages of both components such as the fast crystallization and fully covered film morphology of PbAc2 and the well-grown crystals of PbCl2 but also complemented the drawbacks of each other. Synergistic features of mixed lead precursors were also helpful in fabricating uniform films of well-grown crystals throughout the entire thickness of films via slotdie coating. We confirmed that mixed lead precursors were helpful in overcoming the problems of morphological control in the printing process, which was hard to achieve by using only a single lead source. Owing to these morphological results, we were able to obtain improved device performance with 13.3% PCE and superior reproducibility in the device using mixed lead precursors. Moreover, these mixed lead precursors exhibited more suppressed trap-assisted charge recombination and improved long-term device stability due to less defects and charge trap sites. Finally, we successfully demonstrated the fabrication of a 10 cm2 area module with patterned stripes via slot-die coating and achieved 8.3% PCE. From our results, we were able to confirm that the mixed lead precursors are a promising material system for the fabrication of PeSCs via a printing process.

EXPERIMENTAL SECTION Small device fabrication Patterned 2.0 x 2.5 cm glass/ITO substrates were cleaned successively with deionized water, acetone, and isopropanol in an ultrasonic bath for 15 min and


16

Page 17 of 27 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


treated under UV-ozone for 15 min. PEDOT:PSS (Clevios P VP AI 4083, Heraeus) was spin coated at 5000 rpm for 30 s onto the substrate and then thermally annealed at 150 ℃ for 10 min in air. Two perovskite precursor solutions were prepared: one by dissolving PbAc2·3H2O (Sigma-Aldrich) and the other by dissolving PbCl2 with MAI (Dyesol) in a molar ratio of 1:3 in N,N-dimethylformamide (DMF) at a concentration of 0.75 M. For the mixed lead precursor solution, two prepared solutions were mixed at various ratios. The printing process was conducted in ambient atmosphere by using a slot-die coater based on a 3D-printer system. The perovskite precursor solution was coated onto the PEDOT:PSS layer at a coating speed of 15 mm/s with a gap of 100 µm between the substrate and the meniscus. The solution feed was maintained at 40 µL/min with a syringe pump and a N2 blower system (blown through a nozzle 1.3 mm wide from a distance of 25 mm under 0.04 MPa). The perovskite-coated films were thermally annealed at 100 ℃ for 5 min in air. After that, C60 was spin coated onto the perovskite layer from a dichlorobenzene solution (15 mg/mL) at 1200 rpm for 40 s and then thermally annealed at 105 ℃ for 5 min in a nitrogen-filled glove box. For the electron-transporting layer, a solution of PC61BM in chlorobenzene at a 20 mg/mL was deposited on the C60 layer by spin coating. Lastly, BCP (10 nm) / Ag (80 nm) cathodes were thermally evaporated through a shadow mask for an active area of 0.1 cm2 under vacuum at 10-6 torr.

Module Fabrication Stripe-patterned large-area 8.0 x 3.3 cm glass/ITO substrates were used for module fabrication. The deposition of all of the layers was identical to that of the aforementioned processes for a small device, except for the quantity of casting solution. The edges of the deposited films were slightly scratched for series connections between the sub-cells.


17


Page 18 of 27

Each module consisted of 4 stripes with a 2.5 cm2 active area, so the total active area was calculated as 10 cm2.

Characterization The current density-voltage (J-V) characteristics were evaluated with a Keithley 2400/Oriel solar simulator at an intensity of 100 mW/cm2 (AM 1.5G illumination). For calibration of the illumination-intensity, we used a standard Si solar cell certified by the International System of Units (SI) (SRC 1000 TC KG5 N, VLSI Standards, Inc.). The surface and cross-sectional film morphologies of the perovskite films were analyzed using a scanning electron microscope (SEM, HITACHI S-4700). The external quantum efficiency (EQE) spectrum was measured with a QEX-7 PV Measurements Inc. spectral response system. Device stability was evaluated by recording the device performance as a function of storage time in air while maintaining the humidity under 25% without any encapsulation.

ASSOCIATED CONTENT Supporting Information. Additional data and results (J-V curve, IPCE data of best cell, SEM images without gas-blowing process and resistance values obtained from EIS Measurement) (PDF)

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]


18

Page 19 of 27 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


Present Addresses ‡

School of Materials Science and Engineering (SMSE), Gwangju Institute of Science and

Technology (GIST), 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea. §

Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul

02792, Republic of Korea Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government (NRF-2015R1A2A1A10054466) and the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20163030013900). This work was supported by the GIST Research Institute(GRI) grant funded by the GIST in 2018.

REFERENCES (1)

Stranks, S. D.; Eperon, G. E.; Grancini, G.; Menelaou, C.; Alcocer, M. J. P.; Leijtens, T.; Herz, L. M.; Petrozza, A.; Snaith, H. J. Electron-Hole Diffusion Lengths Exceeding 1


19


Page 20 of 27

Micrometer in an Organometal Trihalide Perovskite Absorber. Science. 2013, 342 (6156), 341–344. (2)

D’Innocenzo, V.; Grancini, G.; Alcocer, M. J. P.; Kandada, A. R. S.; Stranks, S. D.; Lee, M. M.; Lanzani, G.; Snaith, H. J.; Petrozza, A. Excitons versus Free Charges in OrganoLead Tri-Halide Perovskites. Nat. Commun. 2014, 5, 3586.

(3)

Xing, G.; Mathews, N.; Sun, S.; Lim, S. S.; Lam, Y. M.; Grätzel, M.; Mhaisalkar, S.; Sum, T. C. Long-Range Balanced Electron- and Hole-Transport Lengths in OrganicInorganic CH3NH3PbI3. Science. 2013, 342 (6156), 344–347.

(4)

You, J.; Hong, Z.; Yang, Y. (Michael); Chen, Q.; Cai, M.; Song, T.-B.; Chen, C.-C.; Lu, S.; Liu, Y.; Zhou, H.; et al. Low-Temperature Solution-Processed Perovskite Solar Cells with High Efficiency and Flexibility. ACS Nano 2014, 8 (2), 1674–1680.

(5)

Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131 (17), 6050– 6051.

(6)

Best Research Cell Efficiencies. https://www.nrel.gov/pv/assets/images/efficiencychart.png.

(7)

Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. Il. Solvent Engineering for High-Performance Inorganic–organic Hybrid Perovskite Solar Cells. Nat Mater 2014, 13 (9), 897–903.

(8)

Xiao, M.; Huang, F.; Huang, W.; Dkhissi, Y.; Zhu, Y.; Etheridge, J.; Gray-Weale, A.; Bach, U.; Cheng, Y.-B.; Spiccia, L. A Fast Deposition-Crystallization Procedure for


20

Page 21 of 27 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


Highly Efficient Lead Iodide Perovskite Thin-Film Solar Cells. Angew. Chemie 2014, 126 (37), 10056–10061. (9)

Xiao, Z.; Dong, Q.; Bi, C.; Shao, Y.; Yuan, Y.; Huang, J. Solvent Annealing of Perovskite-Induced Crystal Growth for Photovoltaic-Device Efficiency Enhancement. Adv. Mater. 2014, 26 (37), 6503–6509.

(10)

Aldibaja, F. K.; Badia, L.; Mas-Marza, E.; Sanchez, R. S.; Barea, E. M.; Mora-Sero, I. Effect of Different Lead Precursors on Perovskite Solar Cell Performance and Stability. J. Mater. Chem. A 2015, 3 (17), 9194–9200.

(11)

Moore, D. T.; Sai, H.; Tan, K. W.; Smilgies, D.-M.; Zhang, W.; Snaith, H. J.; Wiesner, U.; Estroff, L. A. Crystallization Kinetics of Organic–Inorganic Trihalide Perovskites and the Role of the Lead Anion in Crystal Growth. J. Am. Chem. Soc. 2015, 137 (6), 2350–2358.

(12)

Barrows, A. T.; Pearson, A. J.; Kwak, C. K.; Dunbar, A. D. F.; Buckley, A. R.; Lidzey, D. G. Efficient Planar Heterojunction Mixed-Halide Perovskite Solar Cells Deposited via Spray-Deposition. Energy Environ. Sci. 2014, 7 (9), 2944–2950.

(13)

Razza, S.; Giacomo, F. Di; Matteocci, F.; Cinà, L.; Palma, A. L.; Casaluci, S.; Cameron, P.; D’Epifanio, A.; Licoccia, S.; Reale, A.; et al. Perovskite Solar Cells and Large Area Modules (100 cm2) Based on an Air Flow-Assisted PbI2 Blade Coating Deposition Process. J. Power Sources 2015, 277, 286–291.

(14)

Kim, J. H.; Williams, S. T.; Cho, N.; Chueh, C.-C.; Jen, A. K.-Y. Enhanced Environmental Stability of Planar Heterojunction Perovskite Solar Cells Based on BladeCoating. Adv. Energy Mater. 2015, 5 (4), 1401229.


21


(15)

Page 22 of 27

Wei, Z.; Chen, H.; Yan, K.; Yang, S. Inkjet Printing and Instant Chemical Transformation of a CH3NH3PbI3/Nanocarbon Electrode and Interface for Planar Perovskite Solar Cells. Angew. Chemie 2014, 126 (48), 13455–13459.

(16)

Li, S.-G.; Jiang, K.-J.; Su, M.-J.; Cui, X.-P.; Huang, J.-H.; Zhang, Q.-Q.; Zhou, X.-Q.; Yang, L.-M.; Song, Y.-L. Inkjet Printing of CH3NH3PbI3 on a Mesoscopic TiO2 Film for Highly Efficient Perovskite Solar Cells. J. Mater. Chem. A 2015, 3 (17), 9092–9097.

(17)

Peng, X.; Yuan, J.; Shen, S.; Gao, M.; Chesman, A. S. R.; Yin, H.; Cheng, J.; Zhang, Q.; Angmo, D. Perovskite and Organic Solar Cells Fabricated by Inkjet Printing: Progress and Prospects. Adv. Funct. Mater. 2017, 27 (41), 1703704.

(18)

Hwang, K.; Jung, Y.-S.; Heo, Y.-J.; Scholes, F. H.; Watkins, S. E.; Subbiah, J.; Jones, D. J.; Kim, D.-Y.; Vak, D. Toward Large Scale Roll-to-Roll Production of Fully Printed Perovskite Solar Cells. Adv. Mater. 2015, 27 (7), 1241–1247.

(19)

Giacomo, F. Di; Shanmugam, S.; Fledderus, H.; Bruijnaers, B. J.; Verhees, W. J. H.; Dorenkamper, M. S.; Veenstra, S. C.; Qiu, W.; Gehlhaar, R.; Merckx, T.; et al. UpScalable Sheet-to-Sheet Production of High Efficiency Perovskite Module and Solar Cells on 6-In. Substrate Using Slot Die Coating. Sol. Energy Mater. Sol. Cells 2017.

(20)

He, M.; Li, B.; Cui, X.; Jiang, B.; He, Y.; Chen, Y.; O’Neil, D.; Szymanski, P.; Ei-Sayed, M. A.; Huang, J.; et al. Meniscus-Assisted Solution Printing of Large-Grained Perovskite Films for High-Efficiency Solar Cells. Nat. Commun. 2017, 8, 16045.


22

Page 23 of 27 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


(21)

Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.; Duan, H.-S.; Hong, Z.; You, J.; Liu, Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science. 2014, 345 (6196), 542–546.

(22)

Qing, J.; Chandran, H.-T.; Cheng, Y.-H.; Liu, X.-K.; Li, H.-W.; Tsang, S.-W.; Lo, M.-F.; Lee, C.-S. Chlorine Incorporation for Enhanced Performance of Planar Perovskite Solar Cell Based on Lead Acetate Precursor. ACS Appl. Mater. Interfaces 2015, 7 (41), 23110– 23116.

(23)

Yang, Z.; Chueh, C.-C.; Zuo, F.; Kim, J. H.; Liang, P.-W.; Jen, A. K.-Y. HighPerformance Fully Printable Perovskite Solar Cells via Blade-Coating Technique under the Ambient Condition. Adv. Energy Mater. 2015, 5 (13), 1500328.

(24)

Hsieh, T.-Y.; Wei, T.-C.; Wu, K.-L.; Ikegami, M.; Miyasaka, T. Efficient Perovskite Solar Cells Fabricated Using an Aqueous Lead Nitrate Precursor. Chem. Commun. 2015, 51 (68), 13294–13297.

(25)

Moore, D. T.; Sai, H.; Tan, K. W.; Estroff, L. A.; Wiesner, U. Impact of the Organic Halide Salt on Final Perovskite Composition for Photovoltaic Applications. APL Mater. 2014, 2 (8), 81802.

(26)

Zhang, W.; Saliba, M.; Moore, D. T.; Pathak, S. K.; Hörantner, M. T.; Stergiopoulos, T.; Stranks, S. D.; Eperon, G. E.; Alexander-Webber, J. A.; Abate, A.; et al. Ultrasmooth Organic–inorganic Perovskite Thin-Film Formation and Crystallization for Efficient Planar Heterojunction Solar Cells. 2015, 6, 6142.


23


(27)

Page 24 of 27

Qiu, W.; Merckx, T.; Jaysankar, M.; Masse de la Huerta, C.; Rakocevic, L.; Zhang, W.; Paetzold, U. W.; Gehlhaar, R.; Froyen, L.; Poortmans, J.; et al. Pinhole-Free Perovskite Films for Efficient Solar Modules. Energy Environ. Sci. 2016, 9 (2), 484–489.

(28)

Jeng, J.-Y.; Chiang, Y.-F.; Lee, M.-H.; Peng, S.-R.; Guo, T.-F.; Chen, P.; Wen, T.-C. CH3NH3PbI3 Perovskite/Fullerene Planar-Heterojunction Hybrid Solar Cells. Adv. Mater. 2013, 25 (27), 3727–3732.

(29)

Docampo, P.; Ball, J. M.; Darwich, M.; Eperon, G. E.; Snaith, H. J. Efficient Organometal Trihalide Perovskite Planar-Heterojunction Solar Cells on Flexible Polymer Substrates. Nat. Commun. 2013, 4, 2761.

(30)

Huang, F.; Dkhissi, Y.; Huang, W.; Xiao, M.; Benesperi, I.; Rubanov, S.; Zhu, Y.; Lin, X.; Jiang, L.; Zhou, Y.; et al. Gas-Assisted Preparation of Lead Iodide Perovskite Films Consisting of a Monolayer of Single Crystalline Grains for High Efficiency Planar Solar Cells. Nano Energy 2014, 10, 10–18.

(31)

Conings, B.; Babayigit, A.; Klug, M. T.; Bai, S.; Gauquelin, N.; Sakai, N.; Wang, J. T.; Verbeeck, J.; Boyen, H.; Snaith, H. J. A Universal Deposition Protocol for Planar Heterojunction Solar Cells with High Efficiency Based on Hybrid Lead Halide Perovskite Families. Adv. Mater. 2016, 28 (48), 10701–10709.

(32)

Eperon, G. E.; Burlakov, V. M.; Docampo, P.; Goriely, A.; Snaith, H. J. Morphological Control for High Performance, Solution-Processed Planar Heterojunction Perovskite Solar Cells. Adv. Funct. Mater. 2014, 24 (1), 151–157.


24

Page 25 of 27 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


(33)

Chen, Q.; Zhou, H.; Hong, Z.; Luo, S.; Duan, H.-S.; Wang, H.-H.; Liu, Y.; Li, G.; Yang, Y. Planar Heterojunction Perovskite Solar Cells via Vapor-Assisted Solution Process. J. Am. Chem. Soc. 2014, 136 (2), 622–625.

(34)

Long, R.; Liu, J.; Prezhdo, O. V. Unravelling the Effects of Grain Boundary and Chemical Doping on Electron–Hole Recombination in CH3NH3PbI3 Perovskite by Time-Domain Atomistic Simulation. J. Am. Chem. Soc. 2016, 138 (11), 3884–3890.

(35)

Sherkar, T. S.; Momblona, C.; Gil-Escrig, L.; Ávila, J.; Sessolo, M.; Bolink, H. J.; Koster, L. J. A. Recombination in Perovskite Solar Cells: Significance of Grain Boundaries, Interface Traps, and Defect Ions. ACS Energy Lett. 2017, 2 (5), 1214–1222.

(36)

Mandoc, M. M.; Kooistra, F. B.; Hummelen, J. C.; de Boer, B.; Blom, P. W. M. Effect of Traps on the Performance of Bulk Heterojunction Organic Solar Cells. Appl. Phys. Lett. 2007, 91 (26), 263505.

(37)

Cowan, S. R.; Roy, A.; Heeger, A. J. Recombination in Polymer-Fullerene Bulk Heterojunction Solar Cells. Phys. Rev. B 2010, 82 (24), 245207.

(38)

Rong, Y.; Ku, Z.; Mei, A.; Liu, T.; Xu, M.; Ko, S.; Li, X.; Han, H. Hole-Conductor-Free Mesoscopic TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on Anatase Nanosheets and Carbon Counter Electrodes. J. Phys. Chem. Lett. 2014, 5 (12), 2160–2164.

(39)

Hu, M.; Liu, L.; Mei, A.; Yang, Y.; Liu, T.; Han, H. Efficient Hole-Conductor-Free, Fully Printable Mesoscopic Perovskite Solar Cells with a Broad Light Harvester NH2CH=NH2PbI3. J. Mater. Chem. A 2014, 2 (40), 17115–17121.


25


(40)

Page 26 of 27

Wang, Q.; Chen, B.; Liu, Y.; Deng, Y.; Bai, Y.; Dong, Q.; Huang, J. Scaling Behavior of Moisture-Induced Grain Degradation in Polycrystalline Hybrid Perovskite Thin Films. Energy Environ. Sci. 2017, 10 (2), 516–522.


26

Page 27 of 27 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


Table of Contents / Abstract graphic


27

Slot-Die Coated Perovskite Films Using Mixed Lead Precursors for

Recommend Documents