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Interface engineering based on liquid metal for compactlayer-free, fully printable mesoscopic perovskite solar cells Yumin Zhang, Jianhong Zhao, Jin Zhang, Xixi Jiang, Zhongqi Zhu, and Qingju Liu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00158 • Publication Date (Web): 10 Apr 2018 Downloaded from http://pubs.acs.org on April 10, 2018

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ACS Applied Materials & Interfaces

Interface engineering based on liquid metal for compact-layer-free, fully printable mesoscopic perovskite solar cells Yumin Zhang,§ Jianhong Zhao,§ Jin Zhang, Xixi Jiang, Zhongqi Zhu, Qingju Liu*

Yunnan Key Laboratory for Micro/Nano Materials & Technology, School of Materials Science and Engineering, Yunnan University, Kunming 650091, P. R. China.

KEYWORDS Mesoscopic perovskite solar cell; 5-ammoniumvaleric acid iodine; liquid metal; hole extraction; interface

ABSTRACT A printing process for the fabrication of perovskite solar cells (PSCs) exhibits promising future application in the photovoltaic industry due to its low-cost and eco-friendly preparation. In mesoscopic carbon-based PSCs, however, compared to conventional ones, the hole-transport-layer-free PSCs often lead to inefficient hole extraction. Here, we used liquid metal (LM, Galinstan) as an interface modifier material in combination with a carbon electrode. Based on the consideration of high conductivity and room temperature fluidity, it is found that LMs are superior in improving hole extraction, and more importantly, LMs tend to be reserved at the interface between ZrO2 and carbon for enhancing the contact property. 1

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Correspondingly, the carrier transfer resistance was decreased at the carbon/perovskite interface. As optimized content, the triple mesoscopic PSCs based on mixed-cation perovskite with a power conversion efficiency (PCE) of 13.51% was achieved, involving a 26% augment compared to those without LMs. This work opens new techniques for LMs in optoelectronics and printing.

INTRODUCTION Solar cells based on organic-inorganic hybrid perovskite are considered as one of promising energy supplies in the future, and have recently drawn tremendous research interest since they have demonstrated increased power conversion efficiency (PCE) of up to 22.1%.1 However, conventional perovskite solar cells (PSCs) usually employ expensive

hole

transport

materials

2′,7,7′-Tetrakis(N,N-di-p-methoxyphenyl (Spiro-OMeTAD)2-5

(HTM),

such

as

amine)-9,9′spirobifluorene

or poly(triaryl amine) (PTAA)6-7; furthermore, thermal

evaporated noble metal Au electrodes will increase the cost. Large amounts of perovskite precursor solutions are wasted in the spin coating process, and precisely because of this, the environment is polluted. To obtain high efficiency, many complex controls of film processing such as chlorobenzene-induced fast crystallization for spin-coating proceeding8 and flash-assisted solution for annealing9 were used. Considering the cost reduction and simplified device fabrication process, Han et al. developed the hole-conductor-free fully printable mesoscopic PSC using inexpensive carbon as the back contact.10 Carbon materials possess suitable work functions for extracted holes, hydrophobicity, and outstanding chemical stability. Furthermore, the 2


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screen-printing process for the fabrication can be used for a large-area perovskite device for commercial applications.11-12 Until now, many efforts have been devoted to promoting the performance of this triple mesoscopic layer-based device. However, the micrometer-thick ZrO2 scaffold makes the photogenerated holes have to migrate a long pathway to the carbon electrode. Thus, it is necessary to enhance hole extraction and transportation. Recently, Xu et al. used NiO as a hole selective contact in a mesostructured perovskite solar cell, which highlights the importance of charge extraction.13 Li et al. reported a carbon-based back electrode added with single walled carbon nanotubes (SWCNT), which markedly promoted the performance of mesoscopic perovskite solar cells due to the excellent hole conductivity of SWCNT.14 Zheng et al. utilized boron-doped multi-walled carbon nanotube (MWCNT), which significantly enhances hole extraction in carbon-based perovskite solar cells.15 Yang et al. directly clamped PSC using candle soot and deliberately engineered a hole extraction electrode. For the soot/perovskite interface, a high hole extraction rate of 1.92 ns-1 was achieved.16 Due to the high viscosity and low fluidity of the common carbon paste, the poor contact at the perovskite/carbon interface is always unavoidable. Lately, room temperature liquid metals (LMs), because of the inborn nature of liquid and high conductivity, make them as one of the most promising candidates for engineering applications,

including

printed

electronics,17-20

drug

delivery

systems,21

microfluidics22 and reaction solvent for the room-temperature synthesis of atomically thin metal oxides.23 In this work, we developed a new method for engineering the 3



interface of mesoporous perovskite solar cells by introducing LMs (Galinstan, GaInSn) into the carbon electrode. In terms of printed electronics, electrode materials moderately add LMs with good conductivity, fluidity and high density are expected to form favorable contact between electrodes and the matrix as well as improve the interface charge transfer ability. At the same time, the high temperature volume micro-variation of liquid metal can eliminate the stress change during the annealing process of carbon-based electrode. By varying contents of LMs, the sheet resistance of carbon electrode was successfully reduced, and the contact performance between carbon electrode and perovskite was improved. Ultimately, the triple mesoscopic PSCs based on mixed-cation perovskite (5-AVA)x(MA)1-xPbI3 (5-AVA represents 5-aminovaleric acid; MA represents methylammonium) were prepared. The best photovoltaic performance was achieved by adding 1.2% (weight percentage, the same below) LMs into carbon paste, which displayed a PCE of 13.51% with an effective area of 0.10 cm2. Compared to the control device (merely 10.69%), adding LMs leads to a significant improvement in hole extraction at the perovskite/carbon interface. Furthermore, the approach proves to be a way forward for building flexible micro/nanoelectronics.

EXPERIMENTAL SECTION Perovskite precursor solution. The (5-AVA)x(MA)1-xPbI3 precursor solution was prepared by dissolving 191 mg CH3NH3I (MAI, Dyesol) and 553 mg PbI2 (Youxuan Tech, 99.999%) in 1 ml of γ-butyrolactone (GBL, TCI Chemicals), in which 15 mg HOOC(CH2)4NH3I (5-AVAI, Dyesol) was added; then, the mixed solution was stirred 4


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at 60°C overnight. Carbon electrodes. The carbon paste was prepared as follows: 3 g graphite (6 µm), 1 g carbon black (30 nm) and 0.8 g ZrO2 (50 nm) were added in 15 g terpilenol followed by 24 hours of ball milling. The containing liquid metal (LM, GaInSn) paste was prepared in the same manner except that was mixed a series of contents of LM, 0.6 %, 1.2 %, 2.0 %, and 3.5 %, respectively. Device fabrication: The patterned fluorine-doped tin oxide (FTO) was ultrasonically cleaned by detergent water, deionized water, acetone and absolute ethanol for 15 min, respectively. Then, the mesoporous TiO2 layer (m-TiO2, ~500 nm) was deposited by screen-printing TiO2 paste (Dyesol, diluted with 3.5 times of ethanol) on top of the FTO substrate and then annealed at 500°C for 30 min. The plate was cooled down to room temperature, and a mesoporous ZrO2 layer (m-ZrO2, ~3 µm) was printed over the m-TiO2 layer including a drying at 90°C for 30 min. Finally, the conductive carbon paste was printed as the back contact (~10 µm), which was followed again by drying at 90°C for 30 min, and then annealing at 400°C for 30 min. After cooling down to room temperature, the perovskite precursor solution was infiltrated by drop casting on the top of the carbon counter electrode. After drying at 50°C for two hours, the mesoscopic perovskite solar cells (PSCs) were obtained. Characterization: The morphologies of carbon film and cross-sections of devices were measured by a scanning electron microscope (SEM, HITACHI S-3400N) equipped with an energy-dispersive X-ray spectrometer (EDS, AMETEK EDAX). The X-ray diffraction (XRD) patterns were recorded by an X-ray diffraction system 5



(XRD, TTR-III) using Cu Kα radiation. The UV-Vis absorption spectra (UV-Vis) were carried out on a HITACHI U-4100 spectrometer. Steady-state photoluminescence (PL) and time-resolved PL decay (TRPL) of the (5-AVA)x(MA)1-xPbI3 film on the carbon/glass substrates were measured on a fluorescence spectrometer (EDINBURGH, FS5) with the exciation wavelength of 507 nm. TRPL spectra were measured at 760 nm using excitation with a 450 nm light pulse. A four-point probe (SB100A) was used to measure the sheet resistance. The current density-voltage (J-V) curves were recorded using a Keithley 2400 source meter under simulated sun illumination (AM 1.5G, Zolix) equipped with a 150 W Xenon lamp. The light density was adjusted to 100 mW cm-2 by calibrating with a standard Si solar cell. The typical J-V characteristics were measured by forward scan from -0.2 V to 1.2 V or reverse scan from 1.2 V to -0.2 V at a scan rate of 50 mV s-1. The incident photon-to-current conversion efficiency (IPCE) spectra were measured using a quantum efficiency testing system (Zolix, Solar Cell Scan100) with a monochromator (Omni-λ) and data acquisition units (DCS300PA and SR830). A black mask with a circular aperture (φ 3.6 mm) was used to determine the device area (0.10 cm2). Electrochemical impedance spectroscopy (EIS) characterization was carried out on an electrochemical workstation (CH instruments, CHI660E) in the frequency range of 10 mHz to 1 MHz. The PSCs were measured at a bias of -0.6 V with the amplitude of 50 mV under dark condition. The Zview software (Scribner Associates Inc.) was used to simulate the equivalent circuit. 6


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RESULTS AND DISCUSSION Figure 1a shows variation of the sheet resistances (Rsq) for carbon electrode with the content of LMs on glass and fluorine doped tin oxide (FTO) substrate, respectively. The insert demonstrates that the thickness of prepared carbon film in this paper is approximately 10 µm. With the increasing LM contents (< 1.2%), both the Rsq for the carbon film onto glass and FTO decrease; the Rsq for carbon film onto FTO is visibly lower than that of onto glass under the same LMs addition. This reveals that the substrate conductivity will obviously affect the sheet resistance of the upper film.

Figure 1. (a) Variation of the Rsq for the carbon electrode with the LM contents on glass and fluorine doped tin oxide (FTO) substrate, respectively. (b) EDS of the carbon electrode with 1.2% LMs. (c) Cross-section SEM image of the entire device. (d) Cross-section SEM image and (e) corresponding EDS linear-scan of the element distribution in the interface between ZrO2 layer and carbon layer comprised of 1.2% LMs. 7



Compared with the carbon film without LMs, the incremental contact points between the graphite sheets and the LM particles can help to reduce the carbon film resistance. The LMs (Figure S1) tend to be at the bottom of the film because of its high density and fluidity, the function of which is comparable to FTO; therefore, the Rsq of carbon film decreased. However, with the LM content continuing to increase over 1.2%, the Rsq of the film distinctly increased. LMs possess extremely high surface tension,24 so they tends to reunite when the additive content is in excess (Figure S2), which has an adverse effect on film conductivity. Figure 1b shows the energy-dispersive X-ray spectroscopy (EDS) of carbon film with 1.2% LMs, and the inserted scanning electron microscope (SEM) image corresponds to the scanning area. LMs that can hardly be seen also proved to be at the bottom of the film. The cross-section SEM image of the complete device without perovskite shows that the mesoporous TiO2 (~500 nm) and ZrO2 (~3 µm) were covered by mesoporous carbon film at the top of the device, as shown in Figure 1c. A cross-section SEM image (Figure 1d) and corresponding EDS linear-scan of the element distribution with line width of 1 µm in the interface between ZrO2 layer and carbon layer comprised of 1.2% LMs was conducted. The EDS results are shown in Figure 1e, which identifies the elements corresponding to the cross-sectional SEM image (the yellow dash line marked, “0” indicates the initial scanning position and arrow indicates the scan direction in Figure 1d) and confirms that the LMs exist between ZrO2 and carbon layer. The wettability of γ-butyrolactone (GBL) on the carbon films with different 8


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addition of LMs were analyzed using contact angle (CA) measurements, respectively. Figure 2 presents optical images of the contact-angle with the GBL solvent on the carbon film.

Figure 2. Optical images of the contact angle with GBL solvent on the carbon film with different LMs additions.

During the same time interval, the carbon film containing 1.2% LMs displayed the fastest penetration for the GBL solvent. However, a further increase in the LMs content may lead to blockage of the penetration channels. Therefore, LMs accelerate the infiltration of the GBL solvent, which will benefit for GBL-based perovskite precursor solution. In addition, the optical images of the contact angle 9



characterization for N,N-Dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are shown in Figure S3 and Figure S4, respectively. It also revealed adding 1.2% LMs is relatively reasonable. Thus, it can be concluded that the addition of appropriate amount of LM can effectively improve the wettability and increase the infiltration and filling of perovskite precursor solution on the carbon film. The X-ray diffraction (XRD) patterns of (5-AVA)x(MA)1−xPbI3 perovskite infiltrated into the carbon film with different LM concentrations are shown in Figure 3a. The LM contents were 0%, 0.6%, 1.2% and 2.0%. For convenience, they are described as C, C+0.6% LM, C+1.2% LM, and C+2.0% LM, respectively. Obviously, the diffraction peaks are similar for these samples, which all contain carbon peaks (JCPDS 26-1079), ZrO2 (JCPDS 83-0944) and perovskite (5-AVA)x(MA)1−xPbI3. The diffraction peaks at 14.1°, 20.1°, 23.5°, 28.5°, 31.9°, 35.0°, 40.6°, and 43.2° originated from (100), (110), (111), (201), (211), (221), (202), and (212) planes of (5-AVA)x(MA)1−xPbI3,10, 25-26 respectively. The positions of these peaks are almost unaltered, which proves that adding LMs to the carbon layer does not affect the crystal structure of perovskite. Ultraviolet-visible (UV-Vis) absorption spectra were collected to explore the optical property of (5-AVA)x(MA)1−xPbI3 on mesoporous TiO2, as shown in Figure 3b, where a sharp peak located approximately 372 nm is recognized as the absorption of TiO2 (illustration). Furthermore, the wide absorption spectrum from 300 to 800 nm is due to its small bandgap.25, 27 To accurately reflect this absorption spectrum of perovskite, the spin-coated film on quartz was measured and displayed in Figure S5. Figure 3c showed the steady-state photoluminescence (PL) 10


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spectra of C, C+0.6% LM, C+1.2% LM, and C+2.0% LM. They are used to investigate the efficiency of hole extraction from perovskite. The perovskite infiltrated into carbon layers exhibits PL quenching as the effective charge transfer from perovskite to carbon layer.15, 28 Naturally, the weaker the PL intensity, the better the ability of hole extraction.

Figure 3. (a) XRD patterns of C, C+0.6% LM, C+1.2% LM, and C+2.0% LM, respectively. (b) UV-Vis absorption spectra of TiO2 film filling with (5-AVA)xMA1-xPbI3, inset: UV-Vis absorption spectra of TiO2 film. (c) PL and (d) TRPL spectra of C, C+0.6% LM, C+1.2% LM, and C+2.0% LM, respectively.

In order to more accurately evaluate the dynamics of charge transfer process at perovskite/carbon interfaces, time-resolved PL (TRPL) spectra of the perovskite 11



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band-gap emission at 760 nm for four samples are recorded, and the results are shown in Figure 3d. As shown, the transient PL displayed a biexponential decay including a fast decay component (τ1) and a lower decay component (τ2). τ1 and τ2 corresponding to

trap-controlled

nonradiative

recombination

and

bimolecular

radiative

recombination, respectively.5, 9, 29 From fitting the PL decays where the PL lifetime parameters are listed in Table S1, perovskite infiltrated into carbon film exhibits an average lifetime of 9.07 ns, and subsequently, LMs intensify hole extraction and shorten the time to 6.88 ns, 1.32 ns, and 3.61 ns, respectively. The trend of changes in TRPL is fully consistent with that in steady-state PL intensity. Evidently, adding LMs (the appropriate content is 1.2%) allows more efficient hole extraction from perovskite to carbon electrode, which suppresses electron-hole recombination. Based on the above observations and analysis, it is expected that LMs are promising for optoelectronic applications, especially for printed PSCs. We fabricated compact-free, fully printable mesoscopic PSCs using mixed cation perovskite (5-AVA)x(MA)1−xPbI3 as light harvesters, as shown in Figure 4a. The PSCs using carbon film without and with LMs contents of 0.6%, 1.2%, 2.0%, and 3.5% are labeled as PSC0, PSC0.6, PSC1.2, PSC2.0, and PSC3.5, respectively. Figure 4b presents the energy band alignment of mesoporous PSC.10,

26, 30

Because of the

matching band structure, photogenerated excitons to be dissociated into electrons and holes at the TiO2/perovskite interface, and then, the electrons injected into TiO2 conduct band while the holes will transported into carbon electrode.31-32 The photovoltaic performances of prepared devices were evaluated by measuring their 12


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current density versus voltage (J-V) curves and their incident photon-to-current conversion efficiency (IPCE) spectra. We covered devices with an active area of 0.5 cm2 by a black mask with a circular aperture area of 0.10 cm2. The details can be found in experimental section.

Figure 4. (a) Schematic architecture and (b) energy level diagram of compact-layer-free, fully printable PSCs. (c) the J-V curves of optimized device (PSC1.2) under forward and reverse scan conditions. (d) EQE response and integrated Jsc of PSC1.2. (e) Steady-state photocurrent output at the maximum power point (0.68 V) and its corresponding power output. (f) Long-term stability of the devices without or with LMs stored in atmosphere, inset: the optical images of fresh device (left) and device stored for 50 days (right), respectively. 13



Figure 4c demonstrates the optimized device performance for the LMs content of 1.2% (PSC1.2) utilizing forward and reverse scan at a scan rate of 50 mV s-1 under standard AM 1.5G illumination of 100 mW cm−2. The PCE difference between the forward (13.24%) and reverse (13.51%) scan is small, reflecting negligible hysteresis. The achieved PCE for PSC1.2 exhibits a short-circuit current density (Jsc) of 21.85 mA cm-2, an open-circuit voltage (Voc) of 0.91 V, and a fill factor (FF) of 0.679. The Jsc value obtained from the J-V measurement is matched well (less than 7%) with that obtained by the integration of the external quantum efficiency (EQE) spectra (Figure 4d). Subsequently, we measured steady-state photocurrent output at the maximum power point (0.68 V) for further verifying the reliability of measured PCE and shown in Figure 4e. It can be seen that photocurrent and corresponding PCE rise quickly to the maximum (19.6 mA cm-2 and 13.33%) when the light is turned on and then stabilize with time. The stabilized PCE agrees with the negligible hysteresis. The J-V reverse and forward scans curves for PSC0, PSC0.6, PSC1.2, PSC2.0 and PSC3.5 are summarized in Table 1, respectively. To verify whether the LM particles affect the stability of PSCs, we therefore investigated the long-term stability of our devices stored under ambient atmosphere. The PCEs of PSC0 and PSC1.2 as a function of storage time are shown in Figure 4f. Apparently, the two devices demonstrate commendable stability for 50 days due to the thick hydrophobic carbon electrode, which works as a ‘mesh’ to block the moisture during stored in atmosphere. In terms of the PCEs of PSC1.2, their performance retain above 90% of the initial value. However, a slight increase of PCE in the early days may result from humidity assisted 14


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thermal exposure process reported by Hashmi et al.33 The illustration displays the back views of fresh PSC1.2 and aged (50 days) PSC1.2, after aging, the active area stays dark, indicating that the devices possess very good stability in air. To further confirm the reproducibility of these results, over 30 separate devices were fabricated and characterized under the same conditions for carbon electrode incorporated with different contents of LMs, respectively. The box plots of device performances are shown in Figure 5.

Table 1. Photovoltaic parameters of PSC0, PSC0.6, PSC1.2, PSC2.0 and PSC3.5 under forward scan (FS) and reverse scan (RS), respectively.

Devices

Scan direction

Jsc (mA cm-2)

Voc (V)

FF

PCE (%)

FS

19.50

0.84

0.645

10.57

RS

19.50

0.85

0.651

10.69

FS

20.33

0.87

0.658

11.51

RS

20.33

0.88

0.658

11.77

FS

21.85

0.90

0.673

13.24

RS

21.85

0.91

0.679

13.51

FS

19.43

0.83

0.628

10.13

RS

19.37

0.84

0.631

10.27

FS

17.83

0.82

0.554

8.09

RS

17.80

0.83

0.575

8.49

PSC0

PSC0.6

PSC1.2

PSC2.0

PSC3.5

15



Figure 5. Statistics distribution of (a) Jsc, (b)Voc, (c) FF, and (d) PCE of PSC utilizing carbon electrode incorporated with different LM contents. The top and bottom lines of the boxes represent the upper and lower quartile values, respectively. The bars perpendicular to the box represent the maximum and minimum values. The dots inside the boxes represent the mean value, whereas the lines across the boxes represent the median.

Compared with the control devices without LMs, it can be found that both Jsc and Voc clearly increased when the content of LMs is less than 1.2%. The average PCE is increased from 10.33% to 12.79% for the addition LMs of 1.2%, while an average Voc is increased from 0.84 V to 0.89 V, and Jsc is increased to 21.46 mA cm-2. The improved Voc may be attributed to the decreased sheet resistance of carbon electrode,33-34 as well as the engineered interface contact between perovskite and carbon film through the fluidity and conductivity of LMs would be responsible for 16


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increasing Jsc.35-36 With the continuously increasing LMs, the FF decreases rapidly, leading to the dramatically decrease of PCE. This indicates that excessive LM causes the sheet resistance of the carbon electrode increasing because of agglomeration, and the enrichment LMs at the bottom of carbon film will lead to decline of perovskite filling rate. To further investigate the interfacial charge-transfer processes of these PSCs with and without LMs, the J-V curves of PSC0, PSC1.2 and PSC3.5 were used for contrastive study (Figure 6a), and the Nyquist plots were measured at a bias of -0.6 V with a frequency range from 10 mHz to 1 MHz in the dark by electrochemical impedance spectroscopy (EIS). As shown in Figure 6a, adding LMs is beneficial to carbon electrode to extract holes from perovskite. However, excessive LMs cause a sharp drop in performance due to the decreased FF. According to Figure 6b, two separated semicircles in the Nyquist plot reflect the internal resistance of PSC. The first high frequency arc is usually assigned to carrier transport process at the interface (Rct), whereas the lower frequency arc is attributed to the charge recombination behaviors in device (Rrec).26, 37-38 Obviously, after adding LMs, the radius of the first arc is decreased, while that of the second arc is increased, which indicates more efficient hole extraction and lower recombination rate at the perovskite/LMs incorporated carbon electrode interface. This is consistent with improved Jsc and Voc of the devices. In contrast, the excessive LMs lead to the blockage of the collection of holes and increase the possibility of recombination. The EIS results were fitted with equivalent circuits with an additional contribution from series resistance (Rs), as 17



shown in the inset of Figure 6b. The specific values of Rs, Rct and Rrec are listed in Table S2. Generally, the hole extraction and transport of carbon electrode without and with LMs are schematically illustrated in Figure 6c and 6d, respectively. Due to the high conductivity and density of LM particles, the engineered interface between ZrO2 and carbon electrode increases the hole transport channel, and reduces the possibility of carrier accumulation and recombination.

Figure 6. (a) Comparison J-V data and (b) the corresponding Nyquist plots of PSC0, PSC1.2 and PSC3.5, respectively. Inset: the equivalent circuit fitting from EIS data, in which Rct, Rrec, Rs and CPE represent the charge-transfer resistance, recombination resistance, series resistance, and capacitance, respectively. Schematical graph of the hole extraction and transport of carbon electrode (c) without and (d) with LMs.

18


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CONCLUSIONS In summary, the incorporation of LMs into carbon electrodes for efficient compact-layer-free, fully printable mesoscopic PSC has been successfully fabricated. The optimized devices with 1.2% LMs addition achieved a PCE of 13.51%. Compared with devices (10.69%) without LMs addition, the increased performance of such PSCs results from the improvement of hole extraction ability, and engineered interface between perovskite and carbon electrode through adding LMs. Obviously, LMs can significantly increase the conductivity of the carbon electrode and optimize the contact property between carbon and perovskite. However, excessive LMs are extremely detrimental to the electrode performance due to agglomeration. Our findings show that LMs can serve as an interface modifier material to engineer the electrode contact, especially suitable for printing field.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: Characterization with SEM, UV-Vis, contact angle, and photoelectronic properties.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] ORCID 19



Yumin Zhang: 0000-0002-7457-7465 Jianhong Zhao: 0000-0003-4114-4193 Qingju Liu: 0000-0003-2288-3417 Author Contributions §

These authors contributed equally to this work.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS This work was financially supported by the China National High-tech R&D Program (863 Program, 2015AA034601).

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(17) Ren, L.; Zhuang, J.; Casillas, G.; Feng, H.; Liu, Y.; Xu, X.; Liu, Y.; Chen, J.; Du, Y.; Jiang, L.; Dou, S. X. Nanodroplets for Stretchable Superconducting Circuits. Adv. Funct. Mater. 2016, 26 (44), 8111-8118. (18) Wang, Q.; Yu, Y.; Yang, J.; Liu, J. Fast Fabrication of Flexible Functional Circuits Based on Liquid Metal Dual-Trans Printing. Adv. Mater. 2015, 27 (44), 7109-7116. (19) Zheng, Y.; He, Z. Z.; Yang, J.; Liu, J. Personal electronics printing via tapping mode composite liquid metal ink delivery and adhesion mechanism. Sci. Rep. 2014, 4, 4588. (20) Wang, L.; Liu, J. Pressured liquid metal screen printing for rapid manufacture of high resolution electronic patterns. RSC Adv. 2015, 5 (71), 57686-57691. (21) Lu, Y.; Hu, Q.; Lin, Y.; Pacardo, D. B.; Wang, C.; Sun, W.; Ligler, F. S.; Dickey, M. D.; Gu, Z. Transformable liquid-metal nanomedicine. Nat. Commun. 2015, 6, 10066. (22) Khoshmanesh, K.; Tang, S. Y.; Zhu, J. Y.; Schaefer, S.; Mitchell, A.; Kalantar-Zadeh, K.; Dickey, M. D. Liquid metal enabled microfluidics. Lab Chip 2017, 17 (6), 974-993. (23) Zavabeti, A.; Ou, J. Z.; Carey, B. J.; Syed, N.; Orrell-Trigg, R.; Mayes, E. L. H.; Xu, C.; Kavehei, O.; O'Mullane, A. P.; Kaner, R. B.; Kalantar-Zadeh, K.; Daeneke, T. A liquid metal reaction environment for the room-temperature synthesis of atomically thin metal oxides. Science 2017, 358 (6361), 332-335. (24) Hu, L.; Wang, L.; Ding, Y.; Zhan, S.; Liu, J. Manipulation of Liquid Metals on a 23



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A 2015, 3 (17), 9103-9107. Table of contents

26


Page 26 of 31

a)

b)


FTO

CK

80

OK

Ga L

Si K Zr L

Ga K

0.8

1.6

2.4

0

3.2

2

4

d)

0

e) 0

8

10

Intensity CK

2

Carbon

6

Energy (keV)

LM content (%)

Distance (μm)

1 60 2 40 3 4 20 5 0 6 7 -20 0.0 8 9 c) 10 11 12 13 14 15 16 172 μm 18 19 20 21 22 23 24

Intensity

Sheet Resistance (Ω)

Page 31 100 27 of Glass

ZrO2


TiO2 FTO

5 μm

OK Zr L

4

In L Sn L

6 8 10

Ga K

ZrO2：83-0944 Carbon：26-1079

 

 









Absorbance (a.u.)

C+1.2% LM C+2.0% LM

1.6 1.2

1.0 0.8

Page 28 of 31 TiO2

0.6 0.4 0.2

372 nm

0.0 300

400

500

600

700

800

Wavelength (nm)

0.8 0.4 TiO2/(5-AVA)x(MA)1-xPbI3

20

30

40

50

60

0.0 300

70

400

2-Theta (degree)

500

600

700

800

900

Wavelength (nm) C C+0.6% LM C+1.2% LM C+2.0% LM

PL intensity (a.u.)

1 2 3 4 5 6 10 c)7 8 9 10 11 12 13 14 15 16680 17 18 19 20 21 22 23

 



b)

C

ACS Applied C+0.6% Materials LM 2.0 & Interfaces Absorbance (a.u.)

 (5-AVA)x(MA)1-xPbI3  Carbon   ZrO2

Model Equation

d) 1.0 Normalized PL intensity

Intensity (a.u.)

a)

Plot y0 A1

C C+0.6% LM C+1.2% LM C+2.0% LM

0.8

t1 A2

Wavelength (nm)

800

840

0.99913

Adj. R-Square

Model Equation Plot A1 t1

60

90

120

ExpDec2

0.00555 2.50659 5.36894 0.58214

t2

13.32468

Reduced Chi-Sqr

3.31765E-5

R-Square(COD)

0.99813

Adj. R-Square

0.99811

0.2

30

0.99912

y = A1*exp(-x/t1) + A x/t2) + y 0 Normalized2

A2

0.4

0

0.48937 1.9129E-5

0.0 760

5.32918 24.03051

Reduced Chi-Sqr R-Square(COD)

ACS Paragon Plus Environment 720

0.00559 2.05387

t2

y0

0.6

ExpDec2

y = A1*exp(-x/t1) + A -x/t2) + y 0 Normalized1

150

Time (ns)

t1=9.07 ns，t2=6.88 ns，t3=1.32 ns，t4=3.61 ns

a)

b)

Page 29 of 31

0.0

ACS Applied Materials & Interfaces -0.5 -3.4

-4

Energy (eV)

Carbon m-ZrO2 m-TiO2 FTO

-4.2 -4.7

-5

(5-AVA)x(MA)1-xPbI3

FTO

-5.0 C+LM

-5.4

TiO2

-6

ZrO2

-7 -8

d)

100

EQE (%)

15

0.4

10

40

5

20

Forward scan Reverse scan

0.2

60

0.6

0.8

0 300

1.0

Voltage (V)

400

500

600

700

800

0 900

Wavelength (nm)

f)

15

20 19.6 mA cm-2

12

12

13.33%

8 Light on

Measured at 0.68 V

PCE (%)

16

9

After 50 days 6

In atmosphere

4

ACS Paragon Plus Environment 0 30

60

90

120

Time (s)

150

180

W/O LMs (PSC0) With LMs (PSC1.2)

3 0

10

20

30

Time (Day)

40

50

Integrated Jsc (mA cm-2)

20 80

PCE (%)

Current density (mA cm-2)


1 2 3 4 5 6 7 c) 8 9 20 10 1115 12 1310 14 5 15 160 17 0.0 e) 18 1920 2016 21 2212 238 24 4 25 260 27 0 28 29

-3.9

a) 24

b) 1.0


Page 30 of 31

22

Voc (V)

Jsc (mA cm-2)

0.9

0.8

0.7 PSC0

PSC0

PSC0.6 PSC1.2 PSC2.0 PSC3.5

Devices


Devices

d) 14

PCE (%)

12

FF

1 20 2 3 18 4 5 16 6 c)7 0.8 8 9 0.7 10 110.6 12 130.5 14 150.4 16 17 18 19 20 21 22 23

10

8

ACS Paragon Plus Environment 6 PSC0


Devices

PSC0


Devices

b)

20k ACS Applied Materials & Interfaces Rct Rrec

20

1 15 2 10 3 PSC0 4 5 PSC1.2 5 PSC3.5 6 00.0 0.2 7 c)8 Jh 9 10 11 12 13 14 15 Perovskite 16 17 ZrO2 18 19 20 21 22 23

Rs

16k

-Z'' (Ω)


a) Page 31 of 31

CPE 1

12k

CPE 2

8k PSC0 PSC1.2 PSC3.5

4k 0

0.4

0.6

0.8

1.0

0

4k

8k

d)

Jh

12k

16k

20k

Z' (Ω)

Voltage (V)

Jh

Jh

Jh

Perovskite ACS Paragon Plus Environment Graphite

Carbon black

Liquid metal

Interface engineering based on liquid metal for ... - ACS Publications

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