Band Alignment Strategy for Printable Triple Mesoscopic Perovskite

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Band Alignment Strategy for Printable Triple Mesoscopic Perovskite Solar Cells with Enhanced Photovoltage Jianhong Zhao, Yumin Zhang, Xinbo Zhao, Jin Zhang, Hai Wang, Zhongqi Zhu, and Qingju Liu ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b02104 • Publication Date (Web): 29 Jan 2019 Downloaded from http://pubs.acs.org on January 31, 2019

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ACS Applied Energy Materials

Band Alignment Strategy for Printable Triple Mesoscopic Perovskite Solar Cells with Enhanced Photovoltage Jianhong Zhao,§,‡ Yumin Zhang,§,¶,‡ Xinbo Zhao,§ Jin Zhang,§ Hai Wang,± Zhongqi Zhu,§ Qingju Liu§,* § School

of Materials Science and Engineering, Yunnan Key Laboratory for Micro/Nano Materials

& Technology, Yunnan University, Kunming 650091, China ¶ Department

of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309,

United States ±

Key laboratory of Yunnan Provincial Higher Education Institutions for Organic Optoelectronic

Materials and Devices, Kunming University, Kunming 650214, China

ABSTRACT: Printable triple mesoscopic structure for organic-inorganic hybrid perovskite solar cells (PSCs) have recently obtained significant attention, and they possess a superior long-term stability to those of planar structured PSCs. Compared with planar ones, however, triple mesoscopic structures typically show a lower open-circuit voltages (Voc). Evidence suggests that non-radiative recombination governed by the mismatched energy levels between the perovskite film and the electron transporting layer (or hole transporting layer) is the main cause for

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photovoltage losses. Here we introduced a gradient bilayered zinc tin oxide (ZTO) ETL for fully printed mesoporous PSCs. This approach reduces the energy loss and augments the Voc, which benefits from the suitable matching of cascade level between perovskite and the ZTO ETL. By tuning Zn content, the ZTO films with gradient energy level and different carrier concentrations are acquired. Our optimized device delivers a high Voc of 1.02 V and PCE of 15.86%. These findings provide a simple pathway to design the interface between ETL and perovskite, and to tailor the band alignment to suppress interfacial trap-assisted recombination of fully printed mesoporous PSCs for enhancing Voc and charge extraction simultaneously. KEYWORDS: band alignment, zinc tin oxide, printable triple mesoscopic structure, fermi level, carrier mobility

INTRODUCTION Given that a rapid boosting of power conversion efficiency (PCE) for hybrid organic-inorganic perovskite solar cells (PSCs), which presently exceed 23%,1-2 the crucial challenge moves to improve the long-term stability and upscale the manufacture of PSCs. To date, the conventional PSC device configuration utilize an electron transporting layer (ETL) of TiO2 and a hole transporting layer (HTL) sandwiched the perovskite absorber.3-7 Besides, industrial scale preparing methods, such as screen printing, slot-die coating, and roll-to-roll processing have been used.8-9 Simultaneously, the hole-conductor-free fully printable mesoscopic PSC has also obtained significant traction since the low-cost carbon layer can effectively block the penetration of moisture in the ambient as well the screen-printing is better compatibility to large-scale


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manufacturing.10-13 Nevertheless, further enhancement of the performance in these PSCs requires preferable band alignment to increase the open-circuit voltages (Voc). From the earlier researches, it was realized that the Voc of PSC is attributed to many factors including the bandgap of mixed perovskite,14-16 the difference between Efn (electron quasi-fermi level) and Efp (hole quasi-fermi level),17 radiative recombination in the perovskite absorber and the non-radiative recombination result from the deep-level traps within the perovskite film and the interfacial contacts.18-20 Many efforts to reducing the radiative recombination—mainly converge on the preparation of high-quality perovskite films in planar structure PSCs—have been proposed.21-23 However, obtaining a high-quality perovskite film in a multi-layer porous scaffold is difficult. Furthermore, the main energy losses in PSCs are non-radiative recombinations, which is directly associated with Voc.24 Evidence suggests that non-radiative recombination was largely governed by the mismatched energy levels between the perovskite film and the ETL (or HTL).2529

Taken together, it is of great crucial to reduce the recombinations by band alignment for further

improving the photovoltage to printable triple mesoscopic PSCs. Factually, it has also been demonstrated modifying the conduction band of the ETL can facilitate the photogenerated electrons extraction in the planar PSCs, thus improving the photovoltage.30-32 However, it is still a great challenge to synchronously adjust the energy level matching and promote the charge transformation efficiency in the printable triple mesoscopic PSCs. In this work, we report the development of bilayered amorphous zinc tin oxide (a-ZTO) films with fine-tuned energy level for matching the band of perovskite and enhanced conductivity for accelerating the electron transport. The optimized a-ZTO films were prepared by spray pyrolysis, which is a representative industrial process that will facilitate upscaling. We further verified that the fermi level of a-ZTO can be tailored via tuning the Zn content, which is analyzed by ultraviolet


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photoelectron spectroscopy (UPS). Furthermore, incorporated Zn effectively fills the electron trap states, enhances the electron mobility, and upshifts the fermi level of SnO2. By engineering the band alignment of the a-ZTO layers using different Zn/Sn ratio and then utilizing bilayer ETL, the HTL-free, mesoporous PSCs can reach a PCE of 15.86%, a Voc of 1.02 V, with negligible hysteresis. This material system paves the way to the realization of large-scale production and high-performance PSCs compatible with low-cost process. RESULTS AND DISCUSSION The ZTO films with different Zn contents were prepared by spray pyrolysis at 400℃ using Din-butyltin

bis(2,4-pentanedionate)

(C18H32O4Sn)

and

zinc

acetate

dihydrate

(Zn(CH3COO)2·2H2O) with different mixing ratios in methanol solution. The details are stated in the Experimental Section. The prepared ZTO films, including Zn ions of different molar ratios, are concisely represented as ZTO-5, ZTO-3, ZTO-1.5, ZTO-1 and ZTO-0.5, respectively. Figure 1a presents X-ray diffraction (XRD) patterns of the prepared pristine SnO2 and ZTO films deposited on glass substrate. None of these films showed obvious peaks of ZnO or SnO2 phases, confirming that the prepared films are amorphous structure. To investigate the distribution of doped Zn in SnO2, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) mapping of ZTO-1 film were performed. As shown in Figure 1b, a homogeneous distribution of Sn, Zn and O is demonstrated and a Sn/Zn molar ratio is approximately equal to 1/1. With an eye to the influence of the surface wetting on the perovskite solution, the wettability of the SnO2 and ZTO films was investigated by contact angle measurements, as shown in Figure S1 (Supporting Information).


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Figure 1. (a) XRD patterns of doped SnO2 with different Zn content deposited on glass substrate. (b) SEM image of ZTO-1 film deposited on quartz substrates, and the EDS mapping images of ZTO-1 film for elements: (c) Overlay, (d) Sn, (e) Zn and (f) O.

X-ray photoelectron spectroscopy (XPS) characteristics were performed to prove more clear distinction in the atomic ratio of Zn, Sn and O for the intrinsic SnO2 and ZTO films on glass substrates. Figure 2a, 2b, and 2c show the O1s XPS spectra of SnO2 film, ZTO-3 film and ZTO-1 film, respectively. Fitted by Gaussian-Lorentzian profile, the peaks are centered at 530.3 eV, which originated from the oxygen bonded to the fully coordinated metal (M-O) and 531.5 eV, which originated from the oxygen vacancy (Ovac), respectively.33-34 Compared with intrinsic SnO2, the peak for M-O bonds, working as electron conductance pathways,27 is more prominent in ZTO-3 film. As such, superior electrical properties such as low trap densities and high electron mobility are demonstrated. When considering the effect of Zn content, it can be numerically seen that ZTO1 film shows a lower oxygen vacancy than that of ZTO-3 film. Meanwhile, Sn3d XPS spectra of


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the SnO2 film, ZTO-3 film and ZTO-1 film are shown in Figure 2d, 2e and 2f, respectively. The peak located at 486.5 eV (Sn 3d5/2) is attributed to Sn4+, whereas the other peak located at 494.9 eV (Sn 3d3/2) is attributed to Sn2+. The peak positions and relative intensity of Sn 3d5/2 and Sn 3d3/2 do not show obvious difference for all the films. As calculated from the integrated peak area in the O1s and Sn3d XPS spectra, the atomic ratio between O and Sn are about 1.62, 1.67 and 2.13 in the SnO2, ZTO-3 and ZTO-1 films, respectively.

Figure 2. The O1s and Sn3d XPS spectra of (a) (d) the intrinsic SnO2 film, (b) (e) ZTO-3 film, and (c) (f) ZTO-1 film.

The fermi level of the ETL is critical for achieving optimal band alignment at interfaces of perovskite/ETL. It is reported that the upshifted fermi level can markedly improve the free electron density as well reduce the deep-level traps, therefore the electron transport ability is enhanced.35 In order to clarify the effect on fermi level variation from heteroatom doping, we characterized the


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band structures of SnO2 and ZTO films with ultraviolet photoelectron spectroscopy (UPS) and ultraviolet-visible (UV-Vis) absorption spectra. For comparison, the relevant data of TiO2 are acquired, as shown in Figure 3. From the secondary electron cutoff (Ecutoff) spectrum, the fermi level (EF) and the valence band maximum (EVBM) of SnO2 are determined to be 4.40 eV and 8.33 eV (Figure 3a and 3b), respectively. Those of TiO2 are found to be 4.31 eV and 7.81 eV, respectively. Notably, the deeper EF of SnO2 compared with TiO2 may be caused by deep-level traps as previously reported.36 However, shallower EF with the increase of Zn content is demonstrated. The EF of ZTO-3 and ZTO-1 are evaluated to be 4.36 eV and 4.31 eV (Figure 3d), respectively. The fermi level to the valence band for ZTO-3 and ZTO-1 are evaluated to be both 3.42 eV (Figure 3c). Therefore, incorporated Zn does not only shift the conduction band, but also lift the fermi level of SnO2, which narrows the band offset for charge transfer between the ETL and the perovskite. The VBM spectra of TiO2, SnO2, ZTO-3 and ZTO-1 films also measured by XPS (Figure S2, Supporting Information), the results confirm the same as UPS. Figure 3e show the absorption coefficient of the TiO2, SnO2, ZTO-3 and ZTO-1 films determined by UV-Vis absorption spectra. TiO2 shows a slightly visible light absorption compared with SnO2 and doped SnO2, which is unfavorable for the performance of PSCs owning to the decreased photon flux for perovskite layer. Further, the tauc plots of these films (Figure 3f) are extrapolated and used to estimate their band gap (Eg). Based on the data of mentioned above, the possible band alignment between (5-AVA)x(MA)1-xPbI3 (5-AVA represents 5-ammoniumvaleric acid) perovskite and different ETL is shown in Figure 3g.


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Figure 3. UPS valence band spectra of TiO2, SnO2, ZTO-3 and ZTO-1 films (a) (c) and the UPS cutoff edge of TiO2, SnO2, ZTO-3 and ZTO-1 films (b) (d). (e) Absorption coefficient and the tauc plots (f) of the TiO2, SnO2, ZTO-3 and ZTO-1 films on quartz substrates, determined by the absorption spectra. (g) Possible band alignment of perovskite solar cell based on different ETL according to their fermi levels, conduction bands and bandgaps.

In addition to band alignment, the carrier concentration and mobility also affect the charge transfer. A low mobility of the ETL could lead to charge accumulation at the interface, which will induce an energy barrier to restrain the charge transport. We measured the mobility of SnO2, five kinds of ZTO and TiO2 films by means of Hall effect, which shows in Table 1. Due to the mobility value of the TiO2 and SnO2 are so inferior (98%), methanol (>99.5%) were purchased from Macklin.


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Precursor preparation. C18H32O4Sn and Zn(CH3COO)2·2H2O with different molar ratios were dissolved in certain methanol solution under vigorous magnetic stirring at room temperature, forming a clear colloidal ZTO solution. For preparing ZTO solutions with different Zn contents, concisely, Sn/Zn=5:1 expresses as ZTO-5. The rest can be done in same manner. The (5AVA)x(MA)1−xPbI3 perovskite precursor solution was obtained by mixing MAI (197.5 mg), PbI2 (573.0 mg) and 5-AVAI (13.7 mg) in 1.0 ml GBL and then stirred at 60°C overnight. Device fabrication. The patterned fluorine-doped tin oxide (FTO) substrates (Tec15, Pilkington) were cleaned by ultrasonication with detergent, deionized water, acetone and ethanol for 15 min, separately. Then, the dense ETL (70 nm) of SnO2 or ZTO was deposited by spray pyrolysis carried out using a 50 mM C18H32O4Sn or ZTO solution at 400°C. After spraying, the FTO substrate was sintered at 400°C for 30 min. The gradient ZTO-3/ZTO-1 bilayer film was prepared spray pyrolysis ZTO-3 (20 nm) and ZTO-1 (50 nm) solution in sequence. Afterward, mesoscopic TiO2 layer (m-TiO2, ~500 nm), ZrO2 spacer layer (m-ZrO2, ~2 μm), and carbon counter electrode (~10 μm) were screen printed onto the substrate layer by layer, sintered 40 min at 500°C, 400°C, 400°C, respectively. Finally, the mesoporous layers were infiltrated with perovskite precursor solution and annealed at 50°C for 2 h. Characterizations. The XRD patterns were recorded by an X-ray diffraction system (TTR-III) using Cu Kα radiation. The SEM images and EDS mapping were measured by a S-3400N equipped with an energy-dispersive X-ray spectrometer (AMETEK EDAX). XPS spectra were performed on a Thermo Scientific K-Alpha using monochrome Al Kα (1486.6 eV) radiation. A 400 µm Xray spot was used for XPS analysis. The photoelectron binding energy scale was calibrated to the C1s peak for the C-C bonds at 284.8 eV. UPS spectra were carried out on a Thermo Scientific ESCALAB 250Xi, with the HeI (21.22 eV) emission line employed for excitation. The data were


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acquired at a bias of -10 V. The UV-Vis spectra were determined with a Hitachi U-4100 spectrometer. Hall effect was performed with a Nanometrics HL5500 Hall system. Steady-state PL of the (5-AVA)x(MA)1−xPbI3 films on the glass, glass/SnO2, and glass/ZTO-3/ZTO-1 substrates were measured on a fluorescence spectrometer (EDINBURGH, FS5) with the excitation wavelength of 507 nm. TRPL spectra were measured at 760 nm using excitation with a 450 nm light pulse. Photocurrent density-voltage (J-V) characteristics were recorded using a Keithley 2400 digital source meter under simulated sun illumination (AM1.5G, Zolix) equipped with a 150 W Xenon lamp, giving irradiance of 100 mW cm−2. A black mask with a circular aperture (0.07 cm2), smaller than the active area of the square solar cell (0.7 cm2), was applied on top of the cell. The devices are measured both in forward scan (-0.2 to 1.2 V) and reverse scan (1.2 to -0.2 V) with a scan rate of 50 mV s−1. The EQEs were measured in air by a lock-in amplifier (SR830) coupled with a monochromator (Omni-λ). The EIS characteristics were measured with an electrochemical workstation (CH instruments, CHI660E) in the frequency range of 10 mHz to 1 MHz. Z-view software (Scribner Associates Inc.) was used to simulate the equivalent circuit.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org. Mobility measurements and figures including CA, XPS valance spectra, SEM, UV−Vis, and photoelectronic properties. (PDF) AUTHOR INFORMATION


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Corresponding Author *E-mail: [email protected], Tel: +86 871 65032713. ORCID Jianhong Zhao: 0000-0003-4114-4193 Hai Wang: 0000-0003-2716-7241 Qingju Liu: 0000-0003-2288-3417 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work was financially supported by the China National High-tech R&D Program (863 Program, 2015AA034601).

REFERENCES (1) Jeon, N. J.; Na, H.; Jung, E. H.; Yang, T. Y.; Lee, Y. G.; Kim, G.; Shin, H. W.; Seok, S. I.; Lee, J.; Seo, J. A fluorene-terminated hole-transporting material for highly efficient and stable perovskite solar cells. Nat. Energy 2018, 3, 682. (2) National Center for Photovoltaics. http://www.nrel.gov/pv/assets/images/efficiency_chart.jpg.


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(3) Seo, S.; Jeong, S.; Bae, C.; Park, N. G.; Shin, H. Perovskite Solar Cells with Inorganic Electronand Hole-Transport Layers Exhibiting Long-Term ( approximately 500 h) Stability at 85 degrees C under Continuous 1 Sun Illumination in Ambient Air. Adv. Mater. 2018, 30, e1801010. (4) Zhu, Y.; Deng, K.; Sun, H.; Gu, B.; Lu, H.; Cao, F.; Xiong, J.; Li, L. TiO2 Phase Junction Electron Transport Layer Boosts Efficiency of Planar Perovskite Solar Cells. Adv Sci (Weinh) 2018, 5, 1700614. (5) Yadav, P.; Alotaibi, M. H.; Arora, N.; Dar, M. I.; Zakeeruddin, S. M.; Gratzel, M. Influence of the Nature of A Cation on Dynamics of Charge Transfer Processes in Perovskite Solar Cells. Adv. Funct. Mater. 2018, 28, 1706073. (6) Christians, J. A.; Schulz, P.; Tinkham, J. S.; Schloemer, T. H.; Harvey, S. P.; de Villers, B. J. T.; Sellinger, A.; Berry, J. J.; Luther, J. M. Tailored interfaces of unencapsulated perovskite solar cells for > 1,000 hour operational stability. Nat. Energy 2018, 3, 68-74. (7) Zuo, C.; Bolink, H. J.; Han, H.; Huang, J.; Cahen, D.; Ding, L. Advances in Perovskite Solar Cells. Adv Sci (Weinh) 2016, 3, 1500324. (8) Zuo, C.; Scully, A. D.; Vak, D.; Tan, W.; Jiao, X.; McNeill, C. R.; Angmo, D.; Ding, L.; Gao, M. Self-Assembled 2D Perovskite Layers for Efficient Printable Solar Cells. Adv. Energy Mater. 2018, 1803258. (9) Zuo, C. T.; Vak, D.; Angmo, D.; Ding, L. M.; Gao, M. One-step roll-to-roll air processed high efficiency perovskite solar cells. Nano Energy 2018, 46, 185-192. (10) 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 NH2CHNH2PbI3. J. Mater. Chem. A 2014, 2, 17115-17121.


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Page 23 of 35 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


(11) Mei, A.; Li, X.; Liu, L.; Ku, Z.; Liu, T.; Rong, Y.; Xu, M.; Hu, M.; Chen, J.; Yang, Y.; Gratzel, M.; Han, H. A hole-conductor-free, fully printable mesoscopic perovskite solar cell with high stability. Science 2014, 345, 295-298. (12) Hu, Y.; Zhang, Z.; Mei, A.; Jiang, Y.; Hou, X.; Wang, Q.; Du, K.; Rong, Y.; Zhou, Y.; Xu, G.; Han, H. Improved Performance of Printable Perovskite Solar Cells with Bifunctional Conjugated Organic Molecule. Adv. Mater. 2018, 30, 1705786. (13) Rong, Y.; Hu, Y.; Mei, A.; Tan, H.; Saidaminov, M. I.; Seok, S. I.; McGehee, M. D.; Sargent, E. H.; Han, H. Challenges for commercializing perovskite solar cells. Science 2018, 361, eaat8235. (14) Liang, Y.; Wang, Y.; Mu, C.; Wang, S.; Wang, X.; Xu, D.; Sun, L. Achieving High OpenCircuit Voltages up to 1.57 V in Hole-Transport-Material-Free MAPbBr3 Solar Cells with Carbon Electrodes. Adv. Energy Mater. 2018, 8, 1701159. (15) Du, T.; Kim, J.; Ngiam, J.; Xu, S.; Barnes, P. R. F.; Durrant, J. R.; McLachlan, M. A. Elucidating the Origins of Subgap Tail States and Open-Circuit Voltage in Methylammonium Lead Triiodide Perovskite Solar Cells. Adv. Funct. Mater. 2018, 28, 1801808. (16) Rajagopal, A.; Stoddard, R. J.; Jo, S. B.; Hillhouse, H. W.; Jen, A. K. Overcoming the Photovoltage Plateau in Large Bandgap Perovskite Photovoltaics. Nano Lett. 2018, 18, 3985-3993. (17) Seo, J.; Park, S.; Chan Kim, Y.; Jeon, N. J.; Noh, J. H.; Yoon, S. C.; Seok, S. I. Benefits of very thin PCBM and LiF layers for solution-processed p–i–n perovskite solar cells. Energy Environ. Sci. 2014, 7, 2642-2646. (18) Tress, W.; Marinova, N.; Inganas, O.; Nazeeruddin, M. K.; Zakeeruddin, S. M.; Graetzel, M. Predicting the Open-Circuit Voltage of CH3NH3PbI3 Perovskite Solar Cells Using Electroluminescence and Photovoltaic Quantum Efficiency Spectra: the Role of Radiative and Non-Radiative Recombination. Adv. Energy Mater. 2015, 5, 1400812.


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(19) Bi, D. Q.; Yi, C. Y.; Luo, J. S.; Decoppet, J. D.; Zhang, F.; Zakeeruddin, S. M.; Li, X.; Hagfeldt, A.; Gratzel, M. Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%. Nat. Energy 2016, 1, 16142. (20) Tress, W.; Yavari, M.; Domanski, K.; Yadav, P.; Niesen, B.; Correa Baena, J. P.; Hagfeldt, A.; Graetzel, M. Interpretation and evolution of open-circuit voltage, recombination, ideality factor and subgap defect states during reversible light-soaking and irreversible degradation of perovskite solar cells. Energy Environ. Sci. 2018, 11, 151-165. (21) Zuo, C.; Ding, L. An 80.11% FF record achieved for perovskite solar cells by using the NH4Cl additive. Nanoscale 2014, 6, 9935-8. (22) Liang, P. W.; Liao, C. Y.; Chueh, C. C.; Zuo, F.; Williams, S. T.; Xin, X. K.; Lin, J.; Jen, A. K. Additive enhanced crystallization of solution-processed perovskite for highly efficient planarheterojunction solar cells. Adv. Mater. 2014, 26, 3748-54. (23) Zhang, W.; Saliba, M.; Moore, D. T.; Pathak, S. K.; Horantner, M. T.; Stergiopoulos, T.; Stranks, S. D.; Eperon, G. E.; Alexander-Webber, J. A.; Abate, A.; Sadhanala, A.; Yao, S.; Chen, Y.; Friend, R. H.; Estroff, L. A.; Wiesner, U.; Snaith, H. J. Ultrasmooth organic-inorganic perovskite thin-film formation and crystallization for efficient planar heterojunction solar cells. Nat. Commun. 2015, 6, 6142. (24) Chen, J.; Park, N. G. Causes and Solutions of Recombination in Perovskite Solar Cells. Adv. Mater. 2018, e1803019. (25) Xue, Q. F.; Liu, M. Y.; Li, Z. C.; Yan, L.; Hu, Z. C.; Zhou, J. W.; Li, W. Q.; Jiang, X. F.; Xu, B. M.; Huang, F.; Li, Y.; Yip, H. L.; Cao, Y. Efficient and Stable Perovskite Solar Cells via Dual Functionalization of Dopamine Semiquinone Radical with Improved Trap Passivation Capabilities. Adv. Funct. Mater. 2018, 28, 1707444.


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(26) Yan, L.; Xue, Q.; Liu, M.; Zhu, Z.; Tian, J.; Li, Z.; Chen, Z.; Chen, Z.; Yan, H.; Yip, H. L.; Cao, Y. Interface Engineering for All-Inorganic CsPbI2Br Perovskite Solar Cells with Efficiency over 14. Adv. Mater. 2018, e1802509. (27) Yu, H.; Yeom, H. I.; Lee, J. W.; Lee, K.; Hwang, D.; Yun, J.; Ryu, J.; Lee, J.; Bae, S.; Kim, S. K.; Jang, J. Superfast Room-Temperature Activation of SnO2 Thin Films via Atmospheric Plasma Oxidation and their Application in Planar Perovskite Photovoltaics. Adv. Mater. 2018, 30, 1704825. (28) Tian, C. B.; Mei, A. Y.; Zhang, S. J.; Tian, H. R.; Liu, S.; Qin, F.; Xiong, Y. L.; Rong, Y. G.; Hu, Y.; Zhou, Y. H.; Xie, S. Y.; Han, H. W. Oxygen management in carbon electrode for highperformance printable perovskite solar cells. Nano Energy 2018, 53, 160-167. (29) Gong, X.; Sun, Q.; Liu, S.; Liao, P.; Shen, Y.; Gratzel, C.; Zakeeruddin, S. M.; Gratzel, M.; Wang, M. Highly Efficient Perovskite Solar Cells with Gradient Bilayer Electron Transport Materials. Nano Lett. 2018, 18, 3969-3977. (30) Tavakoli, M. M.; Yadav, P.; Tavakoli, R.; Kong, J. Surface Engineering of TiO2 ETL for Highly Efficient and Hysteresis-Less Planar Perovskite Solar Cell (21.4%) with Enhanced OpenCircuit Voltage and Stability. Adv. Energy Mater. 2018, 8, 1800794. (31) Correa Baena, J. P.; Steier, L.; Tress, W.; Saliba, M.; Neutzner, S.; Matsui, T.; Giordano, F.; Jacobsson, T. J.; Srimath Kandada, A. R.; Zakeeruddin, S. M.; Petrozza, A.; Abate, A.; Nazeeruddin, M. K.; Grätzel, M.; Hagfeldt, A. Highly efficient planar perovskite solar cells through band alignment engineering. Energy Environ. Sci. 2015, 8, 2928-2934. (32) Wu, M. C.; Chan, S. H.; Lee, K. M.; Chen, S. H.; Jao, M. H.; Chen, Y. F.; Su, W. F. Enhancing the efficiency of perovskite solar cells using mesoscopic zinc-doped TiO2 as the electron extraction layer through band alignment. J. Mater. Chem. A 2018, 6, 16920-16931.


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(33) Lim, K. H.; Kim, K.; Kim, S.; Park, S. Y.; Kim, H.; Kim, Y. S. UV-visible spectroscopic analysis of electrical properties in alkali metal-doped amorphous zinc tin oxide thin-film transistors. Adv. Mater. 2013, 25, 2994-3000. (34) Wei, J.; Yin, Z.; Chen, S. C.; Zheng, Q. Low-Temperature Solution-Processed Zinc Tin Oxide Film as a Cathode Interlayer for Organic Solar Cells. ACS Appl. Mater. Interfaces 2017, 9, 61866193. (35) Liu, X.; Liu, Z.; Sun, B.; Tan, X.; Ye, H.; Tu, Y.; Shi, T.; Tang, Z.; Liao, G. 17.46% efficient and highly stable carbon-based planar perovskite solar cells employing Ni-doped rutile TiO2 as electron transport layer. Nano Energy 2018, 50, 201-211. (36) Ali, F.; Pham, N. D.; Bradford, H. J.; Khoshsirat, N.; Ostrikov, K.; Bell, J. M.; Wang, H.; Tesfamichael, T. Tuning the Amount of Oxygen Vacancies in Sputter-Deposited SnOx films for Enhancing the Performance of Perovskite Solar Cells. ChemSusChem 2018, 11, 3096-3103. (37) Zhao, X.; Tao, L.; Li, H.; Huang, W.; Sun, P.; Liu, J.; Liu, S.; Sun, Q.; Cui, Z.; Sun, L.; Shen, Y.; Yang, Y.; Wang, M. Efficient Planar Perovskite Solar Cells with Improved Fill Factor via Interface Engineering with Graphene. Nano Lett. 2018, 18, 2442-2449. (38) Zhang, Y.; Zhao, J.; Zhang, J.; Jiang, X.; Zhu, Z.; Liu, Q. Interface Engineering Based on Liquid Metal for Compact-Layer-free, Fully Printable Mesoscopic Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2018, 10, 15616-15623. (39) Jiang, X.; Xiong, Y.; Zhang, Z.; Rong, Y.; Mei, A.; Tian, C.; Zhang, J.; Zhang, Y.; Jin, Y.; Han, H.; Liu, Q. Efficient hole-conductor-free printable mesoscopic perovskite solar cells based on SnO2 compact layer. Electrochim. Acta 2018, 263, 134-139.


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(40) Wang, Y.; Duan, C.; Li, J.; Han, W.; Zhao, M.; Yao, L.; Wang, Y.; Yan, C.; Jiu, T. Performance Enhancement of Inverted Perovskite Solar Cells Based on Smooth and Compact PC61BM:SnO2 Electron Transport Layers. ACS Appl. Mater. Interfaces 2018, 10, 20128-20135. (41) Zhou, Y.-Q.; Wu, B.-S.; Lin, G.-H.; Xing, Z.; Li, S.-H.; Deng, L.-L.; Chen, D.-C.; Yun, D.Q.; Xie, S.-Y. Interfacing Pristine C60 onto TiO2 for Viable Flexibility in Perovskite Solar Cells by a Low-Temperature All-Solution Process. Adv. Energy Mater. 2018, 8, 1800399. (42) Hong, L.; Hu, Y.; Mei, A. Y.; Sheng, Y. S.; Jiang, P.; Tian, C. B.; Rong, Y. G.; Han, H. W. Improvement and Regeneration of Perovskite Solar Cells via Methylamine Gas Post-Treatment. Adv. Funct. Mater. 2017, 27, 1703060. (43) Li, Y.; Zhao, Y.; Chen, Q.; Yang, Y. M.; Liu, Y.; Hong, Z.; Liu, Z.; Hsieh, Y. T.; Meng, L.; Li, Y.; Yang, Y. Multifunctional Fullerene Derivative for Interface Engineering in Perovskite Solar Cells. J. Am. Chem. Soc. 2015, 137, 15540-7. (44) Carey, G. H.; Abdelhady, A. L.; Ning, Z.; Thon, S. M.; Bakr, O. M.; Sargent, E. H. Colloidal Quantum Dot Solar Cells. Chem. Rev. 2015, 115, 12732-63. (45) Guo, Y. X.; Ma, J. J.; Lei, H. W.; Yao, F.; Li, B. R.; Xiong, L. B.; Fang, G. J. Enhanced performance of perovskite solar cells via anti-solvent nonfullerene Lewis base IT-4F induced trappassivation. J. Mater. Chem. A 2018, 6, 5919-5925. (46) Liu, T. H.; Chen, K.; Hu, Q.; Zhu, R.; Gong, Q. H. Inverted Perovskite Solar Cells: Progresses and Perspectives. Adv. Energy Mater. 2016, 6, 1600457. (47) Leijtens, T.; Eperon, G. E.; Barker, A. J.; Grancini, G.; Zhang, W.; Ball, J. M.; Kandada, A. R. S.; Snaith, H. J.; Petrozza, A. Carrier trapping and recombination: the role of defect physics in enhancing the open circuit voltage of metal halide perovskite solar cells. Energy Environ. Sci. 2016, 9, 3472-3481.


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(48) Shao, Y. C.; Yuan, Y. B.; Huang, J. S. Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells. Nat. Energy 2016, 1, 15001.

Table of Contents Graphic

A band alignment strategy has been developed for fully printable triple mesoscopic PSCs, yielding an enhanced photovoltage of 1.02 V.


28

(a)

Page 29 of 35

(c)


Overlay

ZTO-1

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 1110 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

(b)

ZTO-0.5

ZTO-1.5 ZTO-3 ZTO-5 SnO2

20

30

40

50

1 μm

1 μm 60

2-Theta (degree)

(d)

1 μm

Sn L

(e)

Zn K

1 μm ACS Paragon Plus Environment

(f)

1 μm

OK

ZTO-3

526

528

530

532

534

526

Binding Energy (eV)

(d) Intensity (a.u.)

Sn 3d3/2

530

532

534

536

Binding Energy (eV)

(e)

Sn 3d5/2

528

(c)

526

528

530

532

534

536

Binding Energy (eV)

(f)

Sn 3d5/2

Page 30 of 35 Measured Fitted Background Ovac M-O

(Ovac) (Ovac+OM-O) =47.9%

Sn 3d5/2

Sn 3d3/2

Sn 3d3/2

Intensity (a.u.)

Measured Fitted Background Ovac M-O

(Ovac) (Ovac+OM-O) =50.4%

ACS Applied Energy Materials Measured (Ovac) Fitted (Ovac+OM-O) Background =50.0% Ovac M-O

Intensity (a.u.)

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

(b) Intensity (a.u.)

(a)

ZTO-1 Intensity (a.u.)

SnO2


482

486

490

494

Binding Energy (eV)

Sn/O=1.62

498

482

486

490

494

Binding Energy (eV)

Sn/O=1.67

498

482

486

490

494

Binding Energy (eV)

Sn/O=2.13

498

(d)

Ecutoff=16.91 eV

ZTO-3 ZTO-1

ZTO-3 ZTO-1

Intensity (a.u.)

Intensity (a.u.)

TiO2 SnO2

EVBM-EF=3.42 eV EVBM-EF=3.42 eV

Ecutoff=16.82 eV

Ecutoff=16.86 eV Ecutoff=16.91 eV

EVBM-EF=3.50 eV EVBM-EF=3.93 eV

SnO2 ZTO-1 ZTO-3

-4.7


400

550

700

850

5

2

3

4

hν (eV)

5

16.6

16.8

17.0

17.2

Binding Energy (eV)

-4.23

-4.20

-4.31 -4.40 -4.36

-4.31

-3.9

-5.0

-5.4 FTO

0

Wavelength (nm)

4

-4.28 -4.26

1

250

3

Carbon

(g)

2

Binding Energy (eV)

Perovskite

2

1

ZrO2

3

17.2

TiO2

(αhν)1/2 (a.u.)

4

17.0

TiO2

(f)

SnO2 ZTO-1 ZTO-3

16.8

Binding Energy (eV)

ZTO-1

TiO2

5

16.6

8

ZTO-3

6

SnO2

4

Binding Energy (eV)

Energy (eV)

2

(e) α (×105 cm-1)

(c)

ACS Applied Energy Materials TiO2 SnO2

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

(b)

Intensity (a.u.)

(a) Page 31 of 35

(d)

(c)


Page 32 of 35

Carbon m-ZrO2

2 μm (e)

Glass Control layer Target layer


680 720 760 800 840

Wavelength (nm)

a-ZTO

(f)

m-TiO2 FTO Glass Control layer Target layer

Normalized PL intensity

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

(b)

Intensity (a.u.)

(a)

0

10 20 30 40 50

Time (ns)

15 10 5

0.0

(c)

0.2

0.4

0.6

0.8

Voltage (V) 50

80

20

60

15

40

10

20

Control device Target device

0

0 300

1.0

(d)

Model

50

Equation


Plot

10

Counts

500

600

700

800

0 900

Gaus s y=y0 + (A/(w*s qrt(pi/2)))*exp(2*((x-xc)/w)^2) B 6.71042 ± 1.47393

xc

0.91798 ± 6.30797E-4

w

0.01212 ± 0.00127

40

0.59712 ± 0.06604

Reduced Chi-Sqr

5.80311

R-Square (COD)

0.98948

Adj. R-Square

20

400

y0

A

30

5


Wavelength (nm)

40

0

25

Model

30

Equation Plot

Gaus s y=y0 + (A/(w*s qrt(pi/2)) x-xc)/w)^2) Plot B y0 6.30309 ± 3.876 xc 12.69541 ± 0.04 w 0.63228 ± 0.125 A 27.42803 ± 7.10 Reduced Chi-Sq 13.33156 R-Square (COD) 0.98232 Adj. R-Square 0.92928 Equation

0.9737 Gaus s y=y0 + (A/(w*s qrt(pi/2)))*exp(2*((x-xc)/w)^2) C

y0

6.8696 ± 4.16188

xc

1.01682 ± 0.00164

w

0.01413 ± 0.00477

20

0.58786 ± 0.20202

A

Model


Reduced Chi-Sqr

35.84067

R-Square (COD)

0.91735

Adj. R-Square

0.79339

10

0.89

0.92

0.95

0.98

Voltage (V)

Integrated Jsc (mA cm-2)

20

Counts

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

(b)

100 ACS Applied Energy Materials

EQE (%)

Current density (mA cm-2)

(a) Page 33 25of 35

ACS Paragon Plus Environment 0 1.01 1.04 11.8 12.6

13.4

14.2

PCE (%)

15.0

15.8


(c)

20 15 10 5 0 0.0

Forward scan Reverse scan

Page 34 25 of 35

20

20 20.01 mA cm-2

15

15

15.81%

10

10

5

5

Measured @ 0.79 V

0

0.2

0.4

0.6

0.8

1.0

0 0

50

100

Voltage (V)

150

200

250

300

Time (s)

(d)

100

10

Rrec

Rct

Rs

10-1 8 10

-2

10

-3

10

-4

10

-5

CPE1

CPE2

6 4 2

10-6 -0.2


0.0

0.2

0.4

0.6

Voltage (V)

0 ACS Paragon Plus Environment 0.8 1.0 1.2 0


5

10

15

Z' (kΩ cm ) 2

20

PCE (%)


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

(b)

ACS Applied Energy25 Materials

25

-Z'' (kΩ cm2)


(a)

Page 35 of 35


(b)

Perovskite

m-TiO2

ZTO-1

e-

e - e- e Efn

FTO Carbon

Energy (eV)

FTO

Perovskite

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

ZTO-3

(a)


Voc Efp

h+ h+ + h+ h

m-TiO2 bilayer ZTO

Carbon

Band Alignment Strategy for Printable Triple Mesoscopic Perovskite

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