Influence of N,N-Dimethylformamide Annealing on the Local Electrical

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Influence of DMF-Annealing on Local Electrical Properties of Organometal Halide Perovskite Solar Cells: an AFM Investigation Jiangjun Li, Jing-Yuan Ma, Jin-Song Hu, Dong Wang, and Li-Jun Wan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b07647 • Publication Date (Web): 07 Sep 2016 Downloaded from http://pubs.acs.org on September 12, 2016

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ACS Applied Materials & Interfaces

Influence of DMF−Annealing on Local Electrical Properties of Organometal Halide Perovskite Solar Cells: an AFM Investigation Jiang-Jun Li †, ‡ and Jing-Yuan Ma, †, ‡ Jin-Song Hu, Dong Wang,*, † and Li-Jun Wan *, † †

Beijing National Laboratory for Molecular Science, Key Laboratory of Molecular Nanostructure and

Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China ‡

University of CAS, Beijing 100049, P. R. China

KEYWORDS: perovskite solar cells, solvent annealing, GBs, KPFM, c-AFM ABSTRACT: Organometal halide perovskites have been recognized as a new class of materials for photovoltaic application. Solvent annealing introduced during the crystallization of the bulk or thin film materials can improve the performance of perovskite solar cells. Herein, we present Kelvin probe force microscope (KPFM) and conductive atomic force microscopy (c-AFM) measurements to investigate the local optoelectronic properties of perovskite film after DMF annealing. AFM results show that N, N-dimethylformamide (DMF) annealing induces the recrystallization, yielding the large-size polycrystalline perovskite film. Uniform and higher photocurrent is distributed on the film. However, lower surface potential enhancement and photocurrent are observed at grain boundaries (GBs), illustrating GBs acting as recombination sites are detrimental to photocurrent transport and collection. Our observations provides nanoscale understanding of the device performance improvement after DMF annealing.

Introduction Recently, methylammonium lead iodide perovskites (CH3NH3)PbX3 (where X is the halogen I, Br or Cl) based absorbers are emerging as a new generation of solution-processable, low-cost photovoltaic materials which are abundant in nature.

1−4

The perovskite absorber layer is a direct band gap semiconductor with

optimum band gap, ambipolar carrier transportation properties, high absorption coefficient and high charge carrier mobility.5−10 These properties make perovskite a prospective candidate for the fabrication of highly ACS Paragon Plus Environment


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efficient solar cells and have achieved power conversion efficiencies (PCE) of >20%.11 Great efforts have been made to develop synthetic methods such as spin coating,12,13 coevaporation,14,15 vapor-assisted depositions,16 and post-synthesis treatment, to control the chemical composition, crystalline morphology of the perovskite active layer. To achieve high performance of photovoltaic device, it is desirable to prepare large-grained and well-crystallized perovskite absorber due to its low density of trap and defect state.17, 18 Solution-processed method, one of the cheapest film production processes, is widely used in the preparation of perovskite solar cell. Solvent evaporation and the convective self-assembly process during spinning coat immediately induce the formation of well-crystallized perovskite film due to strong ionic interactions between the metal cations and halogen anions. Generally, γ-butyrolactone, N, N-Dimethylformamide (DMF), dimethyl sulphoxide (DMSO) and N-methyl-2-pyrrolidone are used as effective solvents for lead halides and MAI, yielding a homogeneous perovskite layer with uniform thickness and grains over a large area. However, one issue with solution-processed perovskite thin films is that the polycrystalline films have a relatively small grain size in the range of 100−200 nm due to the rapid reaction of lead iodide (PbI2) and methylamonium iodide (MAI) and the subsequent quick crystallization of these perovskite materials. Solvent annealing has been demonstrated to be an effective method to improve polycrystalline quality of thin films. Study shows that solvent annealing19, 20 can enhance the grain size and crystallinity of the organolead triiodine perovskite and result in high performance of perovskite solar cells. To gain further insight into the effect of solvent annealing on device performance, it is of great interest to investigate local electrical properties of perovskite upon annealing at the nanoscale. Kelvin probe force microscopy (KPFM) and conductive atomic force microscopy (c-AFM) are well-established scanning probe microscopy (SPM) techniques to simultaneously investigate the morphology and the optoelectronic properties at the nanometer scale in the field of organic, hybrid, and inorganic photovoltaics.

21, 22, 25

Several groups

23−27

have already studied the energy band structure and

photoelectric properties of the perovskite polycrystalline film by analyzing the contact potential difference (CPD) in dark conditions and upon illumination. Local photocurrent transduction pathways associated with carriers transport and recombination could be probed by c-AFM. In this scenario, we report SPM investigation of the solvent annealing effect on the local optoelectronic properties of perovskite film. KPFM and c-AFM were used to explore local electronic properties on grains and GBs, leading to a nanoscale understanding of charge separation and transportation of perovskite thin films. By using DMF vapor to treat the CH3NH3PbI3 thin films, we find the increased crystallinity and grain ACS Paragon Plus Environment

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size of CH3NH3PbI3 crystals. SPM measurements clearly indicate that DMF annealing has strong effect on the local charge generation and transportation, which are related to the improved performance of devices. RESULTS AND ANALYSIS Perovskite Films and Device Characterizations Photovoltaic devices were fabricated to evaluate the influence of solvent−annealing on device performance. These devices were structured FTO/compact-TiO2/mesoporous-TiO2/CH3NH3PbI3/spiro-OMeTAD/Au. The detailed photovoltaic parameters are summarized in Table 1 (the J−V characteristics of the best performance devices are shown in Figure S1). The solar cell annealed under DMF has the highest efficiency of 14.0%, while the devices without solvent annealing show efficiency of 12.5%. Open-circuit voltage (Voc) values of the devices are 1.06 V, and do not change after annealing, which is reasonable since Voc value of solar cells is determined by energy difference between the level of electron donor and the level of electron acceptor. In addition, fill factor (FF) and the short-circuit current density (Jsc) increase from 55.3% to 59.1%, 20.6 to 22.3 mA/cm2, respectively. The external quantum efficiency (EQE) of representative devices is supplied in Figure S2.

Table 1. Photovoltaic parameters of the perovskite devices. Average PCE values were obtained from 20 cells for each type of devices.

Surface Potential Measurement of Perovskite films by KPFM. Figure 1a shows the illustration of the sample structure for SPM characterization. The surface morphology of the perovskite films for both unannealed and DMF annealed was characterized by AFM, as shown in Figure 1b, c. It shows that and larger grain size in the annealed film compared with the unannealed film. The larger grain size exceeds the thickness of film leading to significantly improved FF.19 XRD patterns of perovskite films (shown in Figure S3) indicate the two films have the same tetragonal crystal structure.

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Figure 1. (a) Illustration of the AFM setups and device structures of the mesoporous CH3NH3PbI3/m-TiO2/c-TiO2/FTO. AFM topographic images of the CH3NH3PbI3 perovskite films (b) without and (c) after DMF annealing.

Figure 2 displays the corresponding surface potential distribution of perovskite films in dark conditions (upper half) and under illumination (lower half). The full-size surface potential images of the square scanning area are shown in Figure S4. Both unanealed and annealed perovskite films in dark conditions have the same absolute surface work function which is calculated to be about～4.8 eV consistent with the previous literature. 28 Therefore, DMF annealing does not change the energy level of perovskite films. Upon illumination, both the surface potential of perovskite films with and without DMF−annealing increase, indicating the existence of local positive charges. This suggests that holes accumulate in the perovskite layer, while electrons transport to the electron-transport material TiO2 and finally transport to the ground. Furthermore, the surface potential at GBs both in dark conditions and under illumination is higher than on the grains, indicating positively−charged GBs form downward band bending in the space charge region around the GBs, as shown in Figure S5. This is similar to the previous observations reported recently. 23, 27


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Figure 2. AFM topographic images of the CH3NH3PbI3 perovskite films (a) without and (b) with DMF postannealing. (c and d) Corresponding CPD distribution of perovskite films in dark conditions (upper half) and under illumination (lower half). (e and f) Line profiles of surface potential across the perovskite films in dark conditions and under illumination.

Figure 2e, f show the line profiles of surface potential on the perovskite films before and after irradiation. For the unannealed perovskite film, the surface potential difference between the GB and grains is unchanged under illumination, indicating the ability of hole capture at GBs is comparable to grains. However, GBs on the DMF annealed film show a higher surface potential about 50 mV in dark conditions become to only 30 mV under illumination. This observation can be explained by one of the following two scenarios: (1) fewer holes accumulation at GBs than grains due to the barrier resulting from the downward band bending; (2) recombination of a part of photo-induced electrons and holes. (1) is ruled out in view of the same barrier at GBs for both annealed and unannealed perovskite films based on our KPFM measurements. This leaves scenario (2), which implies the GBs most likely act as recombination sites to some extent. ACS Paragon Plus Environment


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Photocurrent Measurement of Perovskite Devices by c-AFM To further understand the carrier transportation and recombination during the photovoltaic process, we used c-AFM to measure the local photocurrent distribution over the perovskite films. Figure 3 shows the topography and corresponding photocurrent (0.1 sun illumination intensity) mapping under a series of bias voltages. As can be seen in Figure 3c, d, current through every single grain is uniform, 27 indicating the fine crystallization of perovskite nanocrystals. It is particularly obvious that current distribution at each bias condition is more uniform on annealed film than unannealed film, as seen in the summarized distribution of current at different bias voltage in Figure 3e. In clear contrast for each bias condition, higher current passes through the CH3NH3PbI3 crystals film upon DMF-vapor annealing treatment, with a smaller current fluctuation. These results further demonstrate that the crystalline quality and electric property of CH3NH3PbI3 thin films are improved after treated by the DMF vapor.


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Figure 3. AFM topographic images of the CH3NH3PbI3 perovskite films (a) without and (b) with DMF postannealing.（c and d）Corresponding photocurrent mapping at different bias. (e) Summarized mean photocurrent at each bias.

It is supposed that during the annealing treatment, the solvent vapor molecular condenses on the surface of perovskite films and dissolves it due to the high substrate temperature. With the limited solvent vapor pressure, the evaporated solvent molecule may cause a quasi-equilibrium process of dissolution and recrystallization, yielding the large grain and high quality perovskite polycrystalline. It is well known that crystal defects and impurities in the GBs may serve as localized energy states in the band gap, which are prone to recombine the carriers due to energy matching. On the other hand, the band bending at GBs create energy states offset between the GBs and grains, which may promote the spatial separation and collection of photogenerated charges and facilitate channeling of the carriers at the GBs. It can be seen in Figure 3c, a portion of GBs reveal higher current than grains even at the low bias of 0.2 V. The effective carriers correlated to the photocurrents at the GBs come from the bulk grains. Once a positive bias exceeds 0.3 V, higher photocurrents go through all the GBs, indicating that GBs act as channels for current to flow rather than recombination sites.27 We ascribe the efficient charge transfer on GBs to the elimination of the barrier by external electric-field compensation of the band bending. The dark contrast at 0.5 V (Figure 3c) may indicate the presence of minor PbI2 phase. However, in comparison to the unannealed film, DMF annealed film reveals that much lower photocurrent flows through the GBs when the bias voltage is in the range of 0.2－0.4 V (Figure 3d), indicating some carriers are trapped by the defects and take place strong recombination. Meanwhile, current transport through some GBs begins to exceed grains. When the bias reachs 0.6 V, higher current flow through GBs but scanning image becomes unstable. This may be caused by the voltage breakdown. Combining the KPFM characterization results, we speculate that some impurity phase is generated at GBs during DMF annealing, which promotes carrier recombination and is harmful to photocurrent collection. Based on previous c-AFM and KPFM measurements, we speculate the intrinsic crystallization of perovskite grains is improved after DMF−annealing while the GBs may act as recombination sites that decrease the photocurrent to some extent. The slightly improved Jsc of device is the compromised result of the two factors. Impedance Spectroscope (IS) Measurement of Perovskite Devices



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To elucidate the differences in the performance for perovskite solid state devices, impedance spectroscopy (IS) characterization was carried out. Figure 4a plots a set of the characteristic impedance spectra patterns obtained for both unannealed and annealed cells at different applied voltages in the working conditions under 0.1 sun illumination. For all the spectra an arc is observed at high frequencies. According to the previous reports, 29, 30 this arc is related to the carriers transport in spiro-MeOTAD. The second arc, at lower frequencies, is due to the combination of the recombination resistance (Rrec) and the chemical capacitance of the film (Cchem). Rrec is inversely related to the recombination rate and Cchem reflects the capability of a system to accept or release additional carriers because of a change in its Fermi level. The fitting of equivalent circuits allows to separate the Rrec under different bias, as shown in Figure 4b. The Rrec extracted from the Nyquist plots for DMF−treated sample is slightly higher than the unannealed sample in a series of wide bias voltage, indicating a lower carrier recombination loss intensity, which confirms the slightly improved Jsc of the devices.

Figure 4. (a) Representative Nyquist plots measured at different applied bias for perovskite solar cells. (b) Recombination resistance resulting from the IS measurements fitting for different applied bias under 0.1 sun illumination.

Conclusion In summary, we investigate the influence of DMF-annealing on local electrical properties of (CH3NH3)PbI3 perovskite film and corresponding devices performance. DMF treatment gives rise to large size perovskite grains, which may contribute to the improvement of the FF of devices.

After DMF-annealing, the

increment CPD at GBs under illumination is lower than that on grains, implying the partial recombination of electrons and holes. Photocurrent flowing through the grains after DMF−annealing becomes higher and more uniform compared to the unannealed film. This suggests that the gentle DMF atmosphere promotes the slow and uniform growth of perovskite nanocrystals, as well as the improved crystallization. The photocurrent through GBs is lower than grains at different bias voltages, indicating the presence of recombination loss at the GBs. Our results demonstrated DMF−treated perovskite film exhibits not only the ACS Paragon Plus Environment

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improved and uniform crystallinity of grains with grain size exceeding its film thickness, but also the presence of recombination loss sites at GBs, which are beneficial and harmful to devices performance respectively. Such comparative studies on local photovoltaic behavior and performance at nanoscale provide in-depth information about the influence mechanism of solvent annealing for the device optimization. Experimental Section Perovskite Film and Solar Cell Fabrication CH3NH3I was first synthesized by reacting the 10 mL HI (57 wt% in water, Sigma-Aldrich) and 24 mL CH3NH2 (40% in methanol, Sigma-Aldrich) at 0 ℃ for 2 h under stirring. The solvents were removed by rotary evaporation at 50 ℃ for 1 h, and the obtained white solid was then washed with anhydrous diethyl ether and finally recrystallized with ethanol. The precursor solution of perovskite was prepared by mixing CH3NH3I with PbI2 (99%, Sigma-Aldrich) at 1:1 mole ratio in anhydrous DMF (99.8%, Sigma-Aldrich) at room temperature for 20 min. The patterned FTO were cleaned by ultrasonication with deionized water, ethanol, acetone and isopropyl, respectively. The FTO substrates were then subjected to an UV/Ozone treatment for 20 min. An approximate 60 nm thick TiO2 blocking layer was deposited on the FTO substrates through spray pyrolysis using a titanium diisopropoxide bis(acetylacetonate) solution (75% in 2-propanol, Sigma-Aldrich) diluted in 1-butanol (1:39, volume ratio) at 450 ℃。Mesporous TiO2 layer (about 260 nm) composed of 20 nm nanoparticle was then prepared by a two-step spin-coating process at 500 r.p.m. and 4,500 r.p.m. for 5 s and 30 s, respectively, by using a commercial TiO2 paste (Dyesol 18NRT, Dyesol) diluted in ethanol (1:5, weight ratio). The as-deposited TiO2 films were dried at 125 ℃ for 30min and gradually heated to 525 ℃ in air, and finally baked at this temperature for 30 min to remove organic components. Finally, the films were treated with UV/Ozone treatment for 20 min. Then 60 µL CH3NH3PbI3 precursor was coated on the as-prepared FTO electrodes by spin-coating process at 5,000 r.p.m in the glove box. During the spin-coating, 120 µL of anhydrous chlorobenzene (Sigma-Aldrich) was quickly dropped in the center of the substrates. The obtained film was dried at 100 ℃ for 10 min. After transferred onto the hot plate for baking 1h, the perovskite films turn dark brown quickly and display mirror-like appearance. Then, the other perovskite film annealed under DMF vapor pressure at 110℃ for 20 min. After cooling to room temperature, 60 µL spiro-OMeTAD solution was spin-coated on



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the perovskite layer as the hole transport layer. Finally, 80 nm of gold was thermally evaporated on the top of the device as a back contact.

Measurement and Characterization X-ray diffraction (XRD) analysis was performed on a Regaku D/Max-2500 diffractometer equipped with a Regaku D/Max（λ= 1.54056 Å, Rigaku Corporation, Tokyo, Japan). Current–voltage characteristics were measured under AM 1.5G illuminations (1000 W/m2) from a solar simulator (Newport, USA) equipped with 450 W Xenon lamp (OSRAM) and a Keithley 2420 source meter. Impedance spectra (IS) were measured using an impedance analyzer (Solartron Analytical, 1260) with a 30 mV amplitude over the frequency range of 1 Hz to 1 MHz under low light intensity (0.1 sun). All the AFM measurements were performed in dark conditions (the glove box was covered with light block curtains) and under continuous visible light (400～ 800 nm) illumination at an angle of ~45°so the probe does not block the incident light. The irradiation was provided by a commercial Sun Full Spectrum Light Source (NBet, Beijing) optical fiber at 20 mW/cm2, which is at the sample surface were about 14 mW/cm2. It is worth reminding that the AFM (Multimode 8, Bruker) laser has the wavelength of above 600 nm (E>2.07 eV). However, the intensity of laser is low and does not affect our measurements significantly. In our frequency modulation KPFM (FM-KPFM), first scan is used for topographic imaging with Peak Force Mode, then the probe is lift in interleave mode and measures the CPD. The frequency modulation applied to the tip is about 2 kHz. A silicon probe coated with Au with force constant: 0.4-1.2 N/m, tip radius: 12 nm (NSG03/Au, NT-MDT) was used for CPD measurement with the lift mode. The c-AFM measurements were performed in contact mode using the same conductive probe coated with Au to record the current between sample and tip when bias voltage was applied to sample.

ASSOCIATED CONTENT

Supporting Information.


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Additional the best performance characteristics of the perovskite devices, EQE, KPFM images, XRD patterns and band alignment diagram. This material is available free of charge via the Internet at http://pubs.acs.org.

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

Author Contributions J.J.L. and J.Y.M. contributed equally to this work. Funding Sources This work was supported by the National Key Project on Basic Research (Grant 2012CB932902), National Natural Science Foundation of China (21127901, 21233010, 21433011, 21373236), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB12020100). Notes

The authors declare no competing financial interest. ABBREVIATIONS KPFM, kelvin probe force microscopy

c-AFM, conductive atomic force microscopy

CPD, contact potential difference

GB, grain boundary ACS Paragon Plus Environment


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PCE, power conversion efficiencies

Jsc, short-circuit current density

Voc, open-circuit voltage

IS, impedance spectroscopy

REFERENCES (1) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131 (17), 6050−6051.

(2) Kim, H.-S.; Lee, C.-R.; Im, J.-H.; Lee, K.-B.; Moehl, T.; Marchioro, A.; Moon, S.-J.; Humphry-Baker, R.; Yum, J.-H.; Moser, J. E.; Grätzel, M.; Park, N.-G. Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%. Sci. Rep. 2012, 2, 591.

(3) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskite. Science 2012, 338, 643-647.

(4) Burschka, J.; Pellet, N.; Moon, S.-J.; Humphry-Baker, R.; Gao, P.; Nazeeruddin, M. K.; Gratzel, M. Sequential Deposition as A Route to High-Performance Perovskite-Sensitized Solar Cells. Nature 2013, 499, 316– 319.

(5) Kazim, S; Nazeeruddin, M. K.; Grätzel, M. and Ahmad. S. Perovskite as Light Harvester: A Game Changer in Photovoltaics. Angew. Chem., Int. Ed. 2014, 53, 2812–2824.

(6) Snaith, H. J. Perovskites: The Emergence of a New Era for Low-Cost, High-Efficiency Solar Cells. J. Phys. Chem. Lett. 2013, 4, 3623−3630.

(7) Boix, P. P.; Nonomura, K.; Mathews, N.; Mhaisalkar, S. G. Current Progress and Future Perspectives for Organic/Inorganic Perovskite Solar Cells. Mater. Today 2014, 17, 16−23.


Page 13 of 16

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


(8) Park, N.-G. Organometal Perovskite Light Absorbers. Toward a 20% Efficiency Low-Cost Solid-State Mesoscopic Solar Cell. J. Phys. Chem. Lett. 2013, 4, 2423−2429.

(9) Kim, H.-S.; Im, S. H.; Park, N.-G. Organolead Halide Perovskite: New Horizons in Solar Cell Research. J. Phys. Chem. C 2014, 118, 5615−5625.

(10) Oga, H.; Saeki, A.; Ogomi. Y.; Hayase, S. and Seki, S. Improved Understanding of the Electronic and Energetic Landscapes of Perovskite Solar Cells: High Local Charge Carrier Mobility, Reduced Recombination, and Extremely Shallow Traps. J. Am. Chem. Soc. 2014, 136, 13818−13825.

(11) Green, M. A.; Emery, K.; Hishikawa, Y.; Warta, W.; D nlop, E. D. Solar Cell Efficiency Tables (Version 45). Prog. Photovoltaics 2015, 23(1), 1−9.

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

(13) Xiao, M.; Huang, F.; Huang, W.; Dkhissi, Y.; Zhu, Y.; Etheridge,J.; Gray-Weale, A.; Bach, U.; Cheng, Y. B.; Spiccia, L. A Fast Deposition-Crystallization Procedure for Highly Efficient Lead Iodide Perovskite Thin-Film Solar Cells. Angew. Chem. 2014, 126 (37), 10056−10061.

(14) Liu, M.; Johnston, M. B.; Snaith, H. J. Efficient Planar Heterojunction Perovskite Solar Cells by Vapour Deposition. Nature 2013, 501, 395−398.

(15) Malinkiewicz, O.; Yella, A.; Lee, Y. H.; Espallargas, G. M.; Graetzel, M.; Nazeeruddin, M. K.; Bolink, H. J. Perovskite Solar Cells Employing Organic Charge-Transport Layers. Nat. Photonics 2014, 8, 128−132.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 16

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

(17) Dong, Q.; Fang.Y.; Shao, Y.; Mulligan, P; Qiu, J.; Cao, L.; Huang, J. Electron-Hole Diffusion Lengths> 175 mm in Solution-Grown CH3NH3PbI3 Single Crystals. Science 2015, 347, 967−970.

(18) Nie, W.; Tsai, H.; Asadpour, R.; Blancon, J.-C.; Neukirch, A. J.; Gupta, G.; Crochet, J. J.; Chhowalla, M.; Tretiak, S.; Alam, M. A.; Wang, H.-L.; Mohite, A. D. High-efficiency Solution-Processed Perovskite Solar Cells with Millimeter-Scale Grains. Science 2015, 347, 522−525.

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

(20) Liu, J.; Gao, C.; He, X.; Ye, Q.; Ouyang, L.; Zhuang, D.; Liao, C.; Mei, J.; Lau, W. Improved Crystallization of Perovskite Films by Optimized Solvent Annealing for High Efficiency Solar Cell. ACS Appl. Mater. Interfaces 2015, 7, 24008−24015.

(21) Jiang, C.-S; Repins, I. L.; Beall, C.; Moutinho, H. R.; Ramanathan, K.; Al-Jassim, M. M. Investigation of Micro-Electrical Properties of Cu2ZnSnSe4 Thin Films using Scanning Probe Microscopy. Sol. Energy Mater. Sol. Cells 2015, 132, 342–347.

(22) Kamkar, D. A.; Wang, M. F.; Wudl, F.; Nguyen, T. Q. Single Nanowire OPV Properties of a Fullerene-Capped P3HT Dyad Investigated Using Conductive and Photoconductive AFM. ACS Nano 2012, 6, 1149–1157.

(23) Edri, E.; Kirmayer, S.; Henning, A.; Mukhopadhyay, S.; Gartsman, K.; Rosenwaks, Y.; Hodes, G. and Cahen, D. Why Lead Methylammonium Tri-Iodide Perovskite-Based Solar Cells Require a Mesoporous Electron Transporting Scaffold (but Not Necessarily a Hole Conductor). Nano Lett. 2014, 14, 1000−1004.


Page 15 of 16

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


(24) Chen, Q.; Zhou, H.; Song, T. B.; Luo, S.; Hong, Z.; Duan, H. S.; Dou, L.; Liu, Y. and Yang, Y. Controllable Self-Induced Passivation of Hybrid Lead Iodide Perovskites toward High Performance Solar Cells. Nano Lett. 2014, 14, 4158−4163.

(25) Yun, J. S.; Ho-Baillie, A.; Huang, S.; Woo, S. H.; Heo, Y.; Seidel, J.; Huang, F.; Cheng, Y.-B.; Green, M. A. Benefit of Grain Boundaries in Organic−Inorganic Halide Planar Perovskite Solar Cells. J. Phys. Chem. Lett. 2015, 6, 875−880.

(26) Kim, G. Y.; Oh, S. H.; Nguyen, B. P.; Jo, W.; Kim, B. J.; Lee, D. G. and Jung, H. S. Efficient Carrier Separation and Intriguing Switching of Bound Charges in Inorganic−Organic Lead Halide Solar Cells. J. Phys. Chem. Lett. 2015, 6, 2355−2362.

(27) Li, J.-J.; Ma, J.-Y.; Ge, Q.-Q.; Hu, J.-S.; Wang, D.; Wan, L.-J. Microscopic Investigation of Grain Boundaries in Organolead Halide Perovskite Solar Cells. ACS Appl. Mater. Interfaces 2015, 7 (51), 28518–28523.

(28) Wang, Q.; Shao, Y.; Xie, H.; Lyu, L.; Liu, X.; Gao, Y.; Huang, J. Qualifying Composition Dependent p and n Self-Doping in CH3NH3PbI3. Appl. Phys. Lett. 2014, 105, 163508-1–163508-5.

(29) Du, T.; Wang, N.; Chen, H.; Lin, H.; He, H. Comparative Study of Vapor- and Solution-Crystallized Perovskite for Planar Heterojunction Solar Cells. ACS Appl. Mater. Interfaces 2015, 7, 3382– 3388.

(30) Kim, H.-S.; Lee, J.-W.; Yantara, N.; Boix, P. P.; Kulkarni, S. A.; Mhaisalkar, S.; Grätzel, M.; Park, N.-G. High Efficiency Solid-State Sensitized Solar Cell-Based on Submicrometer Rutile TiO2 Nanorod and CH3NH3PbI3 Perovskite Sensitizer. Nano Lett. 2013, 13, 2412−2417.

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