Interface Engineering of Perovskite Solar Cell Using a Reduced

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Interface Engineering of Perovskite Solar Cell Using a Reduced-Graphene Scaffold Mohammad Mahdi Tavakoli, Rouhollah Tavakoli, Soheil Hasanzadeh, and Mohammad Hassan Mirfasih J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b05667 • Publication Date (Web): 23 Aug 2016 Downloaded from http://pubs.acs.org on August 24, 2016

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The Journal of Physical Chemistry

Interface Engineering of Perovskite Solar Cell Using a ReducedGraphene Scaffold Mohammad Mahdi Tavakolia*, Rouhollah Tavakolia, Soheil Hasanzadehb, Mohammad Hassan Mirfasihc a

Department of Materials Science and Engineering, Sharif University of Technology, 14588

Tehran, Iran b

Institute of Materials, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015,

Switzerland c

School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656,

Japan *Corresponding author: Email: [email protected] (M.M. Tavakoli) Tel: (852) 54948635. Fax: +98 (21) 6600 5717

ACS Paragon Plus Environment

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Abstract: Interface engineering of solar cell device is a prominent strategy to improve the device performance. Herein, we synthesize reduced-graphene scaffold (rGS) by using a new and simple chemical approach. In this regard, we synthesize a hollow structure of graphene and then fabricate a three-dimensional scaffold of graphene with a superior surface area using electrophoretic process. We employ this scaffold as an interface layer between the electron transfer and absorber layers in perovskite solar cell. The characterization tests and photovoltaic results show that rGS improves the carrier transportation, yielding a 27% improvement in device performance as compared to conventional device. Finally, a power conversion efficiency of 17.2% is achieved for device based on the graphene scaffold. Besides, rGS amends the stability and hysteresis effect of the perovskite solar cell.

Introduction Organic-inorganic perovskite solar cells have generated great interest worldwide due to the rapid progress of device performance from 3.8% to 22.1% within only 5 years.1,2 In a conventional perovskite solar cell, the perovskite film is sandwiched between electron and hole transfer layers (ETL and HTL, respectively). Thus, the generated carriers in the absorber layer need to travel through the ETL and HTL and their interfaces with perovskite layer. In order to increase the power conversion efficiency (PCE), it is necessary to precisely control the carriers along the entire pathway of device.3-6 In this regards, there are many reports on modification of the carriers transportation in solar cell devices using an interface layer. For instance, some researchers employed phenyl-C61-butyric acid methyl ester (PCBM) as an interface layer between the perovskite and ZnO or TiO2 ETL layers.7-11 They showed that PCBM improves the carriers transport and decreases surface recombination and the hysteresis effect, resulting in higher device performance. Kemp et al.9


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deposited a thin ZnO buffer layer on TiO2 ETL by atomic layer deposition (ALD) to decrease the interface recombination, yielding a 10% improvement of device efficiency due to the enhancement of the open circuit voltage (Voc). Recently, many research groups studied the role of graphene in the optoelectronic devices. In fact, graphene with a honeycomb structure, has a high charge carrier mobility up to 106 cm2/V/s, ~98% transmittance throughout the entire visible light spectrum,12-15 and strong potential for photovoltaic applications.16-19 The application of graphene in perovskite solar cells has recently been the focus of several studies.20-25 In this regard, some researchers fabricated nanocomposites of graphene with ZnO and TiO2 nanoparticles and utilized them as an ETL in the perovskite solar cell, resulting in a higher current density and device performance.22 Wang et al.23 demonstrated that the combination of graphene nanoflake and TiO2 nanoparticles could improve the device performance of perovskite solar cell by up to 15.6%, due to efficient charge-collection of electrons. Zhu et al.24 employed a monolayer of graphene quantum dots between perovskite and TiO2 films and improved the device performance from 8.81 to 10.15%. In this work, we introduce a simple chemical procedure to synthesize rGS and utilize it as an interface layer between perovskite and TiO2 films. In fact, rGS is a three-dimensional (3D) graphene with porous structure, high surface area, and good conductivity. In contrast to other works, this is an all-solution processing route that provides a wide pore structure of graphene with high loading of perovskite materials for efficient electron transport. Besides, it has light trapping property that reduces the reflection. Herein, we utilize the rGS electrode in the perovskite

solar

cell

architecture.

Compared

with

TiO2/perovskite

and

TiO2/2D

graphene/perovskite devices, enhanced photo-induced current density without Voc drop is reported for rGS-based device. The results of characterization tests such as time-resolved


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photoluminescence (TRPL), electrochemical impedance spectroscopy (EIS), and external quantum efficiency (EQE) illustrate that rGS works as a fast extraction layer for electrons, decreases the charge-transfer resistance and increases the current density, respectively, resulting in an efficient perovskite solar cell with a PCE as high as 17.2%.

Results & Discussion An rGS electrode was fabricated as follows: First, a quasi core-shell structure of ZnO/graphene QDs was synthesized by a solution process as explained in Ref. 16. Briefly, the graphene oxide QDs (Figure S1) were synthesized by electrolysis16 of a graphite rod and mixed with a solution of zinc acetate dihydrate in DMF. After 5 hours, a quasi core-shell structure of ZnO/graphene QDs with ~ 4 nm average size was attained, as shown in figure S2. The TEM images (Figure S2a, b) show that the interplanar spacing of ZnO QDs and graphene nanoshell are 0.26 nm (for (002)) and 0.14 nm, respectively. Also, energy-dispersive x-ray spectroscopy (EDAX) analysis (Figure S2c) and x-ray diffraction pattern (Figure S2d) support the formation of a quasi core/shell structure of zinc oxide/graphene QD.12,17 Secondly, a diluted hydrochloric acid solution (5 wt%) was used to remove the ZnO core from the core-shell structure. Thus, the ZnO/graphene QDs were dispersed in the acidic solution with aggressive stirring for 2 h at 50ºC. This treatment leached out the ZnO core, and the warped graphene shells were partially unfolded and formed a cluster. Figure 1a shows a cluster of reduced graphene oxide after removing the ZnO core. As seen, this structure is porous with many holes, which is consisted of several ultrathin graphene layers. In fact, the structure may be the result of agglomeration of graphene shells after dissolving the ZnO core. As shown in Figure 1b,


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the interatomic spacing of the shells is 0.14 nm which is matched with graphene. In order to confirm the composition of the graphene cluster, EDAX analysis of the selected area (marked A in Fig. 1a) is performed. As can be seen in Figure 1c, the composition of this cluster is pure carbon with negligible amount of oxygen. In addition, X-ray photoelectron spectroscopy (XPS) confirms the removal of the ZnO core (Figure S3).

Figure 1. TEM images of the graphene cluster formed after acid leaching. The structure is composed of ultrathin graphene layers with nano-holes. EDAX analysis of the selected area, marked A in figure 1a, indicates the removal of the zinc oxide from the nanocomposite.


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Figure 2 shows the Raman and UV-visible spectra of the graphene clusters. As can be seen in figure 2a, there are three peaks at 1346.4 (D band), 1578.5 cm-1 (G band), and 2668 cm-1 (2D band), which are related to the existence of defects and disorders in the graphitic sheets after ZnO removal, the vibration of sp2-bonded carbon in the graphene lattice, and a shell with a few layers of graphene, respectively. The high ID/IG ratio shows the enhancement of the disorder level in the graphene cluster after removing the ZnO core. A blue shift in the absorption peak of the graphene clusters (from 375 nm to 268 nm) confirms the removal of the ZnO core (Figure 2b). Thirdly, an rGS electrode is deposited on TiO2-coated FTO glass using electrophoretic deposition (EPD) from a solution of graphene clusters. Figure 3a and S4 show the top-view and cross-sectional SEM images of rGS, indicating a porous structure with large surface area. Figure 3b shows the transmittance spectra of the rGS layer compared to the two-dimensional (2D) graphene layer (see more details in electronic supporting information (ESI)), and TiO2-coated FTO glass. The results indicate that the graphene layers (2D or 3D structure) decrease the transmittance. Interestingly, the rGS demonstrates a higher transmittance than the 2D graphene layer due to the light trapping property.


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Figure 2. The characterization of the rGS film. (a) Raman spectrum of the rGS film. (b) UVvisible spectra of the ZnO/graphene QDs and rGS films. Figures 3c shows the top-view and cross-sectional SEM images of CH3NH3PbI3 perovskite film on the rGS layer fabricated by a two-step solution process explained in the ESI, indicating a highly crystalline perovskite film. Meanwhile, the effect of interface layer on perovskite film and its crystal size is studied by using high-resolution SEM. As shown in Figure S5, the morphology of perovskite film is influenced by its interface layer. The results indicate that the average grain size of perovskite film on top of graphitic interface layer is larger than TiO2-based film. Moreover, the rGS-based film has the largest grain size, indicating a high quality perovskite film. The XRD pattern of perovskite film on top of the rGS is in good agreement with the literature and shows a highly crystalline structure of perovskite film with a cubic crystal structure (Figure 3d).8


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Figure 3. (a) Top-view SEM image of the rGS structure, (b) transmittance spectra of the rGS, 2D graphene, and TiO2 films, (c) top-view SEM image of perovskite film on rGS, and (d) XRD pattern of perovskite film.

Figure 4a shows a cross-sectional SEM image of the perovskite solar cell on the rGS electrode. In the device architecture, the FTO glass is coated by a thin film of TiO2 blocking layer. The 2D and 3D reduced graphene oxide is deposited on the TiO2-coated FTO glass by an EPD method. Thereafter, the perovskite film (~300 nm) is formed on top of the electrode using a two-step solution process, followed by an annealing process at 100ºC for 45 min. To complete the device structure, the HTL i.e., 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) is spin-coated on the perovskite film, and finally 100 nm-thick gold is thermally evaporated as top electrode. Figure 4b shows the current density-voltage (J-V) of


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perovskite devices based on different types of ETLs under simulated AM 1.5G solar irradiation in the air. The results demonstrate that the device on the rGS has a PCE as high as 17.2% with a short current density (Jsc) of 22.8 mA/cm2, a Voc of 1.05 V, and a fill factor (FF) of 72%. This indicates 13% and 27% improvement compared with the devices on 2D graphene layer and conventional devices, respectively. The figures of merit for all the devices are summarized in Table 1. As can be seen, the Voc of the devices on different electrodes remains almost unchanged. In fact, the role of the graphene layer at the interface is the enhancement of the Jsc and FF of solar cell devices. In addition, the external quantum efficiency (EQE) of the devices is in good agreement with the results of the J-V measurement, as shown in figure 4c. On the other hand, the rGS increases the EQE of the perovskite device, resulting in a higher Jsc. Furthermore, the device based on the rGS illustrates a higher EQE than the device on 2D graphene layer due to its light trapping property inside the rGS (Figure 3b) and the larger surface area in contact with perovskite film. Moreover, the rGS has another significant role in the perovskite solar cell, and that is, reducing the hysteresis effect. Figure 4d shows the J-V measurements of the devices on the rGS, 2D graphene, and TiO2 using forward and reverse scan directions. Note that the result of the J-V measurements for device on rGS electrode are slightly different compared with counterpart devices, as indicated in Table S1.


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Figure 4. Characteristics of perovskite solar cells based on different interfacial layers such as an rGS, which acts as a fast electron extraction layer. (a) Cross-sectional SEM image of the device on the rGS (inset image is the high magnification of cross-sectional area which is shown by red box), (b) J-V curves under 1.5 AMG indicate the performance of the devices, (c) EQE spectra, (d) J-V measurement of devices in forward and reverse scan directions, and (e) stability of the devices in an ambient environment (~65% humidity) after encapsulation using UV-cured epoxy.


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Moreover, the rGS electrode improves the stability of the perovskite device, as shown in Figure 4e. In this case, all devices were sealed by using UV-cured epoxy and measured over one month in the ambient environment (~65% humidity). The results indicate that the PCE of device on the rGS drops only 20% of the initial value after 30 days, which is more stable than TiO2-based device with 65% loss. Table 1. Figure of merits for the prepared perovskite solar cells based on the rGS, 2D graphene, and TiO2 (All values are the average values of 12 devices)

Average Maximum Rs PCE PCE (Ω) (%) (%)

Device

Voc

Jsc

FF

Rct

based on

(v)

(mA/cm2)

(%)

TiO2

1.04±0.05

19.1±1.1

68±3

11.7±1.8

13.5

27.8 247.1

2D graphene

1.05±0.02

20.7±0.8

70±1

13.6±1.7

15.3

21.2 108.4

rGS

1.05±0.03

22.8±0.9

72 ±2

16.2±1

17.2

17.6

(Ω)

92.7

To further study the role of rGS electrode on device performance and support our findings, TRPL and EIS measurements are employed, as illustrated in Figure 5a and 5b, respectively. The result of the TRPL measurements shows that perovskite films on the rGS and 2D graphene layer have shorter lifetime than TiO2-based one, as shown in Figure 5a. The fitting parameters of the corresponding PL decay curves are shown in Table S2. As seen, the device on the rGS has the shortest lifetime compared with counterpart devices (17% and 98% lower than devices on 2D graphene and TiO2, respectively).19 The results of steady-state photoluminescence are consistent with the TRPL results, as demonstrated in Figure S6. In fact, the quenching effect in the presence of graphene is primarily caused by the static quenching and charge transfer reactions.22 In addition to dynamic quenching, static quenching occurs when the donor and acceptor materials


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are in the ground state, resulting in an improvement of efficient charge carrier extraction. Moreover, the carriers transfer is also faster than the charge recombination process using the rGS electrode, as evidenced by the TRPL measurement. Besides, the role of rGS electrode is investigated by electrochemical impedance spectroscopy (EIS) analysis. Figure 5b shows the results of EIS tests for perovskite devices on the rGS, 2D graphene layer, and TiO2. As seen, the Nyquist curves of the devices have plotted in dark condition (Z′ vs. −Z″), where Z′ and Z″ are the real and imaginary parts of the cell impedance, respectively. As illustrated in Figure 5b and Table 1, the charge-transfer resistance of the devices based on the graphene electrode is lower than TiO2 one due to the smaller radius of the semicircle. Here, the rGS device shows the lowest charge-transfer resistance. The values of ohmic resistance and charge-transfer resistance for rGS device are calculated using the inset model in Figure 5b, which are 17.6 and 92.7 Ohm, respectively. The calculated values from the EIS curves are shown in Table 1. The results confirm that the rGS device has fast electron transport properties and lower carrier recombination compared with its counterpart, as witnessed by the higher Jsc. The results of the TRPL and EIS tests for the rGS-based device demonstrate the faster and more efficient electron transfer than radiative and/or nonradiative decay of photoexcitations, resulting in the lower charge recombination process.26-30 Beside ultraviolet photoelectron spectroscopy (UPS) was employed to study the band alignment diagram of perovskite device on the rGS, as shown in Figure 5c. The Fermi level of the rGS is calculated from the curve in Figure 5d. He I (21.2 eV) is utilized as photon source for UPS measurement. It is worth pointing out that the band level of the rGS matches with the perovskite film very well, and as a result, the electrons are transferred from the perovskite film into the TiO2


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ETL easily through the rGS electrode. In the rGS-based device, the photo-generated electrons flow from rGS to TiO2 ETL due to the lower energy level of TiO2 as compared to rGS.

Figure 5. Device characterizations. (a) Time-resolved PL spectra of perovskite film based on different interfacial films, (b) EIS spectra of the perovskite solar cells on different interfacial layers, (c) Band diagram of perovskite solar cells on rGS, and (d) The rGS work function was measured using an ultraviolet photoelectron spectrum (UPS).

In fact, our findings indicate that the rGS electrode is matched with perovskite film well due to its suitable work function. As mentioned in the literature23,24, there are many defects and recombination sites on the surface of TiO2 film, result in lower current density in the perovskite solar cell. Thus, the presence of an interface layer such as rGS can help to improve the efficiency


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of device by passivation of the dangling bonds on the surface of TiO2 ETL. Owning to the properties of rGS such as excellent charge transfer, high conductivity, fast extraction of electrons, larger surface area, and light trapping properties, we establish a highly efficient perovskite solar cell based on rGS electrode.

Conclusions In summary, we present a new all solution processing approach to fabricate a porous structure of graphene (rGS) on FTO glass. This method is based on the synthesis of a quasi core/shell structure of ZnO/graphene QDs and dissolution of ZnO core using an acidic solution, following by EPD of graphene clusters. We employed rGS as an interface layer for fabrication of perovskite solar cell. Compared with conventional devices, rGS-based perovskite solar cell shows better charge transfer and lower carrier recombination, resulting in higher Jsc (30%) and PCE. Furthermore, the lower work function of the rGS than the conduction band of perovskite film may facilitate the transferring of the photo-induced electrons to the rGS with better conductivity. Our findings suggest that an rGS electrode could serve as an excellent interface layer in a perovskite solar cell, which improves the carriers transfer and the PCE of the device. Finally, a PCE of 17.2% with low hysteresis is achieved based on rGS electrode.

AUTHOR INFORMATION *Corresponding author Email: [email protected] (M.M. Tavakoli) Tel: (852) 54948635. Fax: +98 (21) 6600 5717

Notes The authors declare no competing financial interests.


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ACKNOWLEDGMENT We thank funding support from the Grant Program of Sharif University of Technology (No. G930305) and Elite National Institute.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. It presents the experimental methods, the characterization and analysis tests of graphene oxide quantum dots and ZnO/graphene QDs, photoluminescence spectra of perovskite devices on different substrates, AFM analysis of GO sheets, and the details of J-V measurement results.

REFERENCES (1) Lee, J. W.; Kim, H. S; Park, N. G. Lewis Acid–Base Adduct Approach for High Efficiency Perovskite Solar Cells. Acc. Chem. Res. 2016, 49, 311–319. (2) Tavakoli, M. M.; Tsui, K. H.; Zhang, Q.; He, J.; Yao, Y.; Li, D.; Fan, Z. Highly Efficient Flexible Perovskite Solar Cells with Antireflection and Self-Cleaning Nanostructures. ACS Nano 2015, 9, 10287-10295. (3)

Zhou, H.; Chen, Q.; Li, G.; Luo, S.; Song, T.B.; Duan, H.S.; Hong, Z.; You, J.; Liu,

Y.; Yang, Y. Interface Engineering of Highly Efficient Perovskite Solar Cells. Science 2014, 345, 542-546. (4)

Tavakoli, M.M.; Lin, Q.; Leung, S.F.; Lui, G.C.; Lu, H.; Li, L.; Xiang, B.; Fan, Z.

Efficient, Flexible and Mechanically Robust Perovskite Solar Cells on Inverted Nanocone Plastic Substrates. Nanoscale 2016, 8, 4276-4283. (5) Leung, S. F.; Zhang, Q.; Tavakoli, M. M.; He, J.; Mo, X.; Fan, Z. Progress and Design Concerns of Nanostructured Solar Energy Harvesting Devices. Small 2016, 12, 2536– 2548.


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Page 16 of 20

(6) Tavakoli, M. M.; Mirfasih, M. H.; Hasanzadeh, S.; Aashuri, H.; Simchi, A. Surface Passivation of Lead Sulfide Nanocrystals with Low Electron Affinity Metals: Photoluminescence and Photovoltaic Performance. Phys. Chem. Chem. Phys. 2016, 18, 12086-12092. (7) Qiu, W.; Buffière, M.; Brammertz, G.; Paetzold, U.W.; Froyen, L.; Heremans, P.; Cheyns, D. High Efficiency Perovskite Solar Cells Using a PCBM/ZnO Double Electron Transport Layer and a Short Air-Aging Step. Org. Electron. 2015, 26, 30-35. (8) Tavakoli, M.M.; Gu, L.; Gao, Y.; Reckmeier, C.; He, J.; Rogach, A.L.; Yao, Y.; Fan, Z. Fabrication of Efficient Planar Perovskite Solar Cells Using a One-Step Chemical Vapor Deposition Method. Sci. Rep. 2015, 5, 14083. (9) Kemp, K. W.; Labelle, A. J.; Thon, S. M.; Ip, A. H.; Kramer, I. J.; Hoogland, S.; Sargent, E. H. Interface Recombination in Depleted Heterojunction Photovoltaics Based on Colloidal Quantum Dots. Adv. Energy Mater. 2013, 3, 917–922. (10) Xiong, J.; Yang, B.; Cao, C.; Wu, R.; Huang, Y.; Sun, J.; Zhang, J.; Liu, C.; Tao, S.; Gao, Y.; et al. Interface Degradation of Perovskite Solar Cells and its Modification Using an Annealing-Free TiO2 NPs Layer. Org. Electron. 2016, 30, 30-35. (11) Wu, R.; Yang, B.; Zhang, C.; Huang, Y.; Cui, Y.; Liu, P.; Zhou, C.; Hao, Y.; Gao, Y.; Yang, J. Prominent Efficiency Enhancement in Perovskite Solar Cells Employing Silica-Coated Gold Nanorods. J. Phys. Chem. C 2016, 13, 6996-7004. (12) Steim, R.; Choulis, S. A.; Schilinsky, P.; Brabec, C. J. Interface Modification for Highly Efficient Organic Photovoltaics. Appl. Phys. Lett. 2008, 92, 093303. (13) Dong, H. P.; Li, Y.; Wang, S. F.; Li, W. Z.; Li, N.; Guo, X. D.; Wang, L. D. Interface Engineering of Perovskite Solar Cells with PEO for Improved Performance. J. Mater. Chem. A 2015, 3, 9999-10004.


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Page 17 of 20

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


(14) Tavakoli, M. M.; Tayyebi, A.; Simchi, A.; Aashuri, H.; Outokesh, M.; Fan, Z. Physicochemical Properties of Hybrid Graphene–Lead Sulfide Quantum Dots Prepared by Supercritical Ethanol. J. Nanopart. Res. 2015, 17, 1-13. (15) Tavakoli, M. M.; Simchi, A.; Aashuri, H. Supercritical Synthesis and In Situ Deposition of PbS Nanocrystals with Oleic Acid Passivation for Quantum Dot Solar Cells. Mater. Chem. Phys. 2015, 156, 163-169. (16) Tavakoli, M. M.; Aashuri, H.; Simchi, A.; Kalytchuk, S.; Fan, Z. Quasi Core/Shell Lead Sulfide/Graphene Quantum Dots for Bulk Heterojunction Solar Cell. J. Phys. Chem. C 2015, 119, 18886-18895. (17) Yeo, J. S.; Kang, R.; Lee, S.; Jeon, Y. J.; Myoung, N.; Lee, C. L.; Kim, D. Y.; Yun, J. M.; Seo, Y. H.; Kim, S. S.; et al. Highly Efficient and Stable Planar Perovskite Solar Cells with Reduced Graphene Oxide Nanosheets as Electrode Interlayer. Nano Energy, 2015, 12, 96-104. (18) Tavakoli, M. M.; Tavakoli, R.; Davami, P.; Aashuri, H. A Quantitative Approach to Study Solid State Phase Coarsening in Solder Alloys Using Combined Phase-Field Modelling and Experimental Observation. J. Comput. Electron. 2014, 13, 425-431. (19) Son, D. I.; Kwon, B. W.; Do Yang, J.; Park, D. H.; Seo, W. S.; Lee, H.; Yi, Y.; Lee, C. L.; Choi, W. K. Charge Separation and Ultraviolet Photovoltaic Conversion of ZnO Quantum Dots Conjugated with Graphene Nanoshells. Nano Res., 2012, 5, 747-761. (20) Tavakoli, M. M.; Simchi, A.; Fan, Z.; Aashuri, H. Chemical Processing of ThreeDimensional Graphene Networks on Transparent Conducting Electrodes for DepletedHeterojunction Quantum Dot Solar Cells. Chem. Commun. 2016, 52, 323-326. (21) You, P.; Liu, Z.; Tai, Q.; Liu, S.; Yan, F. Efficient Semitransparent Perovskite Solar Cells with Graphene Electrodes. Adv. Mater. 2015, 27, 3632-3638.


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(22) Tavakoli, M. M.; Tavakoli, R.; Nourbakhsh, Z.; Waleed, A.; Virk, U.S.; Fan, Z. High Efficiency and Stable Perovskite Solar Cell Using ZnO/rGO QDs as an Electron Transfer Layer. Adv. Mater. Interfaces 2016, DOI: 10.1002/admi.201500790. (23) Wang, J. T. W.; Ball, J. M.; Barea, E. M.; Abate, A.; Alexander-Webber, J. A.; Huang, J.; Saliba, M.; Mora-Sero, I.; Bisquert, J.; Snaith, H.J.; et al. Low-Temperature Processed Electron Collection Layers of Graphene/TiO2 Nanocomposites in Thin Film Perovskite Solar Cells. Nano Lett. 2013, 14, 724-729. (24) Zhu, Z.; Ma, J.; Wang, Z.; Mu, C.; Fan, Z.; Du, L.; Bai, Y.; Fan, L.; Yan, H.; Phillips, D. L.; et al. Efficiency Enhancement of Perovskite Solar Cells Through Fast Electron Extraction: The Role of Graphene Quantum Dots. JACS, 2014, 25, 3760-3763. (25) Tavakoli, M. M.; Aashuri, H.; Simchi, A.; Fan, Z. Hybrid Zinc Oxide/Graphene Electrodes for Depleted Heterojunction Colloidal Quantum-Dot Solar Cells. Phys. Chem. Chem. Phys. 2015, 17, 24412-24419. (26) Son, D. I.; Kwon, B. W.; Park, D. H.; Seo, W. S.; Yi, Y.; Angadi, B.; Lee, C. L.; Choi, W. K.; Emissive ZnO-Graphene Quantum Dots for White-Light-Emitting Diodes. Nat. Nanotechnol. 2012, 7, 465-471. (27) Wang, H.; Wang, G.; Ling, Y.; Qian, F.; Song, Y.; Lu, X.; Chen, S.; Tong, Y.; Li, Y. High Power Density Microbial Fuel Cell with Flexible 3D Graphene–Nickel Foam as Anode. Nanoscale 2013, 5, 10283-10290. (28) Tavakkoli, M. M.; Abbasi, S. M. Effect of Molybdenum on Grain Boundary Segregation in Incoloy 901 Superalloy. Mater. Design 2013, 46, 573-578. (29) Yong, V.; Tour, J. M.; Theoretical Efficiency of Nanostructured Graphene‐Based Photovoltaics. Small 2010, 6, 313-318.


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(30) Geim, A. K.; Novoselov, K. S. The Rise of Graphene. Nat. Mater. 2007, 6, 183-191.


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Interface Engineering of Perovskite Solar Cell Using a Reduced

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