Letter - ACS Publications - American Chemical Society

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Aug 8, 2017 - Da Seul Lee,. †. Benjamin ... Martin A. Green,. † and Anita ..... (4) Yang, W. S.; Park, B.-W.; Jung, E. H.; Jeon, N. J.; Kim, Y. C.; Lee,. D. U.; Shin ...
Overcoming the Challenges of Large-Area High-Efficiency Perovskite Solar Cells Jincheol Kim,† Jae Sung Yun,*,† Yongyoon Cho,† Da Seul Lee,† Benjamin Wilkinson,† Arman Mahboubi Soufiani,† Xiaofan Deng,† Jianghui Zheng,† Adrian Shi,† Sean Lim,‡ Sheng Chen,† Ziv Hameiri,† Meng Zhang,† Cho Fai Jonathan Lau,† Shujuan Huang,† Martin A. Green,† and Anita W. Y. Ho-Baillie*,† †

Australian Centre for Advanced Photovoltaics (ACAP), School of Photovoltaic and Renewable and Engineering, University of New South Wales, Sydney 2052, Australia ‡ Electron Microscope Unit, University of New South Wales, Sydney, NSW 2052, Australia S Supporting Information *

ABSTRACT: For the first time, we report large-area (16 cm2) independently certified efficient single perovskite solar cells (PSCs) by overcoming two challenges associated with largearea perovskite solar cells. The first challenge of realizing a homogeneous and densely packed perovskite film over a large area is overcome by using an antisolvent spraying process. The second challenge of removing the series resistance limitation of transparent conductor is overcome by incorporating a metal grid designed using a semidistributed diode model. A 16 cm2 perovskite solar device at the cell level rather than at the module level is demonstrated using the modified solution process in conjunction with the use of a metal grid. The cell is independently certified to be 12.1% efficient. This work paves the way toward highly efficient and large perovskite cells without single-junction perovskite solar cells and silicon−perovskite tandems.

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performance and limiting the development of large-area PSCs. Other deposition techniques have been attempted, such as blade coating,13−15 roll to roll printing,16,17 and spraying.18−21 However, device performance in these works still lags behind those fabricated by spin coating.3,10,11,22,23 To date, a promising technique to control the nucleation and crystal growth kinetics for high-quality perovskite film is the use of antisolvent crystallization.10,24−28 Although such processes can produce a high-quality film, the dropping of antisolvent during spinning is effective only over a small area. While parallel efforts were made on developing antisolvent spraying for perovskite film deposition29 on a small area (0.09 cm2), here we report a spray antisolvent (SAS) method that is suitable for a large area to facilitate rapid nucleation and uniform crystallization of a large-area perovskite film with densely packed grains. To circumvent the quadratic scaling of series resistance (RS) with cell width, one method is to physically isolate the largearea device into thin strips followed by series connection,30 which can be a combination of laser ablation, physical scribing,

he past few years have seen the rapid progress in a new class of solar cells based on mixed organic−inorganic halide perovskites.1 The highest certified power conversion efficiency (PCE) of a perovskite solar cell of 22.1% has been achieved on an aperture area of 0.046 cm2.2 For more realistic photovoltaic (PV) performance evaluation, PCE measured for cell area ≥1 cm2 is encouraged, and some promising results for ≥1 cm2 devices have been reported recently. Certified PCE at 19.6% for a 1.0 cm2 device has been demonstrated using a vacuum-flash assisted solution process.3 To date, the highest certified efficiency for a close to 1 cm2 perovskite solar cell is 19.7%.4 The highest certified PCE for a Si−perovskite tandem is 23.6% on an area of 1 cm2.5 Two main challenges prohibit the creation of larger efficient perovskite solar cells. Both effects limit maximum device area to a few square centimeters. The first problem is the dramatic reduction in perovskite film quality and uniformity for areas much larger than 1 cm2. The second problem is the approximately linear increase in series resistance with cell area. Perovskite layer deposition via spin coating has been widely used to fabricate a dense and uniform absorber film and represents the state of the art.3,6−12 However, as cell size grows, film uniformity declines beyond acceptable levels, degrading © XXXX American Chemical Society

Received: June 30, 2017 Accepted: August 8, 2017

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DOI: 10.1021/acsenergylett.7b00573 ACS Energy Lett. 2017, 2, 1978−1984

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Letter

ACS Energy Letters

Figure 1. Perovskite film on 5 cm × 5 cm FTO substrate. Schematic illustration of the processes, optical images of the entire films, and SEM images from the corner and from the center of the preannealed perovskite films fabricated using the (a) DAS process and (c) SAS process. Optical images of the entire films, SEM images from the corner and from the center of the films, and UV−visible absorptions (spot size of 0.45 cm2) at the various positions of the postannealed (100 °C for 20 min) perovskite films by (b) DAS and (d) SAS. The scale bar in SEM images is 150 μm.

the effects of different spraying pressure and time on the microstructure of the film. Results are shown in Figure S1. It was found that spraying pressure is the key parameter as it determines droplet size, number of droplets, and nozzle flow rate.33 When the spraying pressure is too low, the antisolvent droplet size is too large and the number of droplets are not sufficient to induce sufficient nucleation sites for uniform film growth, resulting in holes in the film (Figure S1a). When the spray pressure is sufficiently high, the droplet size becomes smaller and the number of droplets increases, thereby increasing the number of perovskite nucleation sites, resulting in more compact and dense films, as observed in Figure S1b,c. Another advantage of increasing the spraying pressure is the ability to deliver the antisolvent at a high speed to drive the supersaturation at a faster rate than the conventional drop and spin antisolvent process. In the case when the perovskite film is fabricated by the DAS method, the speed of dispersion and the area of coverage are limited by the speed limit of the spin coater, which relies on the centrifugal force from the spinning to deliver the antisolvent across the surface. For the SAS method, the dimethyl sulfoxide (DMSO) to dimethylformamide (DMF) ratio in the perovskite precursor is also optimized as this is related to the amount and properties of DMSO-PbI2 complexes24 which affect the film crystallization process.34,35 It is found that a DMSO content of 20% in DMF (which is used for all device fabrication in this work) results in the best cell performance for the DAS and SAS methods (Figure S2).

or chemical etching and metal deposition requiring highprecision alignment to minimize “dead-area” losses.31 This architecture is acceptable for a single-junction perovskite module, but it is unsuitable if the PSC is to be incorporated into a tandem such as Si−perovskite tandem cell, which also prevents current matching and optimal optical design. Another solution to the series resistance problem is the use of a metal grid such as that reported in the literature 32 which demonstrated an “inverted” perovskite cell on 25 cm2 at 6.8% according to in-house measurement. In this work, we present a semidistributed diode model for the optimization of metal grid design and implement the metal grid to reduce the series resistance of a 16 cm2 cell without any isolation and alignment steps. By combining the advantages of the modified perovskite deposition method using SAS and the implementation of a metal grid, we have demonstrated a large-area 16 cm2 cell with a certified efficiency at 12.1%. This is the highest certified efficiency for a perovskite device larger than 10 cm2 at the cell level rather than at the module level. The Supporting Information contains the fabrication details of the (HC(NH2)2PbI3)0.85(CH3NH3PbBr3)0.15 perovskite film (with 5 mol % of excess PbI2) by a conventional antisolvent process that involves the dropping of antisolvent (DAS) and the modified antisolvent processes. The modified antisolvent process involves the spraying of antisolvent during the last stage of the perovskite precursor spinning process. As part of the optimization, we investigated 1979

DOI: 10.1021/acsenergylett.7b00573 ACS Energy Lett. 2017, 2, 1978−1984

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processed perovskite film. This is favorable as it has been shown to result in improved cell performance.38 To obtain insights into the film quality in terms of carrier dynamics, we also conducted the time correlated single-photon counting (TCSPC) measurements on five different regions (center and four corners) of the test structures perovskite/mTiO2/bl-TiO2/FTO/glass fabricated by the DAS and SAS methods (Figure S6a). Figure S6b,c shows the measured PL decay traces and the fitted curves for each region of the two samples. Table S2 summarizes the results of the biexponential fitting (see Materials and Methods in the Supporting Information for details). The SAS sample has a shorter τ1 than the DAS sample because of higher carrier extraction.8,12,39 The resultant better device performance will be reported later in this Letter. τ2, which corresponds to charge carrier recombination, is also lower in the SAS sample compared to the DAS sample. τeff summarized in Table S2 has a large spread in the DAS sample compared to the SAS sample (also see Figure S6b−d) because of larger variation in film quality across the DAS sample. PL imaging on full devices fabricated by DAS (Figure S7a) and SAS (Figure S7b) methods was performed at open-circuit conditions. Figure S7e shows the corresponding image intensity distributions. The area-averaged luminescence intensity counts represent the accumulated photogenerated charge carrier density at open-circuit conditions and thus effective carrier lifetime, which are very similar for the two cells. This finding is similar to results from the TCSPC measurements showing comparable lifetimes between the samples. However, a greater nonuniformity is observed across the device fabricated by the DAS technique (cf. Figure 2a,b).

To compare the uniformity of the films prepared by the DAS and SAS methods, perovskite films are deposited on 5 cm × 5 cm fluorine doped tin oxide (FTO) coated glass substrates. The same spin coating parameters such as spinning speed and time are used for both processes. The difference is in the method of delivery of the antisolvents. Figure 1a shows an optical image and scanning electron microscopy (SEM) images of the perovskite film fabricated by the DAS immediately after the spinning process and before annealing. The upper SEM image was taken near the corner of the substrate, while the lower SEM image was taken near the center of the substrate. Figure 1b shows the optical images of the DAS processed perovskite film after annealing, which has been transformed from a yellow transparent film to a dark opaque film. Ultraviolet (UV)−visible absorption measurements (spot size of 0.45 cm2) were also carried out on the four corners and the center of the film. Figure 1c,d shows similar images and absorption spectra but for the film fabricated by SAS. Before annealing, the film deposited by the conventional DAS has a sparse network of dendrites with voids (the brighter regions are the underlying FTO) as seen in the SEM images in Figure 1a. In addition, the morphology of these features changes with position on the substrate. The absorption data for the annealed film at various positions also reveal nonuniformity (Figure 1b). A radial pattern can be observed in the optical image (inset in the absorption graph in Figure 1b) of the annealed film revealing the limitation of the spinning in delivering the antisolvent uniformly across a large surface. The film made by the new SAS process shows superior surface coverage and denser features (Figure 1c). The denser feature is a result of enhanced interaction between the perovskite precursor and the sprayed antisolvent droplets, which are fine and abundant. No radial pattern can be observed in the optical image for the film in Figure 1d. The absorption curves are identical at different positions, and the SEM images in Figure 1d confirm excellent film uniformity. It is important to note that another advantage of using the spraying process to deliver the antisolvent is material savings and less wastage. The amount of antisolvent used by the SAS method is only 30% of that required for the DAS method. Figure S3 shows the result when an equivalent amount of chlorobenzene (CBZ) required for spraying is used for the dropping process. Apart from the radial pattern observed showing nonuniformity, the regions near the corners of the sample show inadequate delivery of the antisolvent over a large area that could otherwise be achieved if the spraying method is used. Figure S4 shows the X-ray diffraction (XRD) patterns of the films made by the DAS and SAS processes before and after annealing. Before annealing, the samples exhibit XRD peaks at around 6.6°, which are related to the presence of the intermediate phase of DMSO-Pb2+. This is confirmed (1017 cm−2 signature) by Fourier transform infrared spectroscopy (FTIR) measurements10,36,37 (Figure S5). Although the annealed DAS and SAS films have similar grain size (Figure S4c,f), XRD patterns reveal that there are some differences in crystal structure. We calculated the integral peak area for the (110), (200), and (220) perovskite phases and the (110)/ (200) and (220)/(200) ratios (Table S1). For the SAS processed sample, the integral peak areas are slightly larger than those for the DAS processed sample, indicating a better crystalline phase. The slightly higher (110)/(200) and (220)/ (200) ratios also indicate stronger (110) orientation in the SAS

Figure 2. Electroluminescence images of full devices fabricated by (a) DAS and (b) SAS methods. The corresponding (c, d) current transport efficiency ( f T) maps and (e, f) f T distributions of the same devices. The scale bars are 3 mm. 1980

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Figure 3. Local (center and four corners) solar cell performance for a perovskite solar cell on a 2 cm × 2 cm substrate fabricated by the (a) DAS and (b) SAS methods. The local solar cell efficiencies were measured under standard AM 1.5G illumination using a 0.159 cm2 aperture with the total cell area of 1.6 × 1.0 cm2.

Figure 4. Current density−voltage (J−V) curves for (a) 1.2 cm2 devices using DAS and SAS methods, (b) 5.8 cm2 device by SAS, and (c) 16.0 cm2 device by SAS. Inset image in panel c is an optical image of the device. The solid lines are fitted light J−V curves through the “semidistributed diode” model. The table summarizes the electrical parameters as well as the RS, RSH, and m(V) values from the fittings.

We also performed EL imaging40 on these cells to obtain further insights into the resistive and carrier recombination losses. In particular, to quantify the nonuniformity which is more prominent in the cell fabricated by the DAS method, the current transport efficiency ( f T) maps were calculated41 (see Materials and Methods in the Supporting Information for details). The corresponding f T maps are shown in Figure 2c,d, while f T distributions are shown in Figure 2e,f. It is found that the peak value of f T for the cell fabricated by the DAS approach (Figure 2c) is lower than that of the SAS approach (Figure 2d). The relationship between f T(x, y) (as a function of x and y) and the spatially varying series resistance, Rs(x, y); terminal voltage, V(x ,y); and dark current density, j(x, y), is expressed in eq 140,41 as follows: ∂j 1 = 1 + R s(x , y) (x , y) fT (x , y) ∂V

narrower distribution of f T for the SAS device indicates better uniformity in the electrical properties when compared to the DAS device (see standard deviation values provided in the inset Tables of Figures 2e and 2f). We note that the tail at low f T for the SAS cell (Figure 2f) is associated with the damage caused by scratches (see Figure S7 and caption for explanation). To confirm the benefits of the SAS method over the DAS method, full devices of structure gold/spiro-OMeTAD/perovskite/m-TiO2/bl-TiO2/FTO/glass (Figure S7) were first fabricated on 2 cm × 2 cm substrates. We measured the current density−voltage (J−V) characteristics of the different regions (center and four corners) of the cell using a round aperture of 0.159 cm2 as shown in Figure 3. The cell fabricated by the SAS process has a higher efficiency with smaller spread of performance across the device. The higher voltage also confirms better film quality consistent with what was observed in the SEM, XRD, time-resolved-PL measurements. The superior FF in the SAS device agrees with the improved current transport efficiency as observed from EL imaging. Using the SAS method, we have achieved an independently certified (by Newport) PCE at 18.1% for 1.2 cm2 cell (Figure S9). A certified JSC of 21.4 mA/cm2 and a FF of 74.6% is achieved for

(1)

We therefore can conclude that the accumulative series resistance and effective dark saturation current in the DAS device are higher than those fabricated in the SAS device.40 This explains the higher fill factor (FF) found in the SAS devices which will be discussed later in this Letter. The 1981

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Figure 5. (a) Measured and modeled J−V curves (inset is photo of the cell), (b) measured and (c) modeled m−V for a 16 cm2 cell fabricated by SAS method with a metal grid. The solid line is the fitted light J−V curve through the “semi-distributed diode” model. The table summarizes the electrical parameters as well as the RS, RSH, and m(V) values from the fitting.

this cell. In particular, a VOC of 1.13 V is among the highest for the state-of-the-art cells. To illustrate the effect of increased series resistance on largearea cells, 5.8 and 16 cm2 cells without metal grid were fabricated (using the SAS method), and the results are shown in Figure 4. To accurately account for the distribution of RS over the area of these large cells, we utilize a semidistributed diode model (see the Supporting Information for detailed methods and Figure S10c for the equivalent circuit). Although it has been common practice to determine RS and RSH from the gradients of the light J−V curve at open-circuit voltage (VOC) and short-circuit current (JSC), respectively, there can be multiple causes to the gradients. For very large-area cells, RS can be large enough to cause a nonzero gradient near JSC, which can appear to indicate a low RSH value. Similarly, when RS is large, a change in RSH has a similar effect on the J−V curve to a change in photocurrent. The ideality factor as a function of voltage (m−V) curve derived from the dark J−V curve contains useful information about the cell parameters. When the light J−V curves (Figure 4) and m−V curves (Figure S10) are fit simultaneously using the “semi-distributed diode” model with parameters listed in Table S3, the J−V parameters become more tightly constrained, allowing (i) the lower limit of RSH to be found; (ii) a more accurate account of RS; and (iii) the reporting of local ideality factor, which is a good indicator of cell quality. The reason for using a diode model that is semidistributed is to avoid excessive computational complexity while still allowing accurate reproduction of experimental J−V curves to quantify the parasitic losses in the large-area cells. The parasitic resistances and minimum local ideality factors of the large-area cells without metal grid from the fitting are listed in the table in Figure 4. The effect of cell size on resistive loss is apparent with RS increasing with area. The minimum local ideality factor (m−V) of the 1.2 cm2 cell approaches 2, indicating that recombination is trap-limited. The minimum m−V of the larger cells is significantly higher, being closer to 3. RSH is reasonably larger (>1000 Ω·cm2) for all cells displaying no trend with cell size. This indicates that surface coverage is consistently high, with no shunting paths through the perovskite. Using the lumped-resistance method as described in the Supporting Information (under Materials and Methods), three grid designs were modeled (see Figure S11 for modeled J−V curves and Table S4 for grid width and spacing). The trade-off

between series resistance (reduces with metal coverage) and shading (increase with metal coverage) is apparent. Figure 5 shows the J−V and m−V characteristics of a 16 cm2 cell with a metal grid using the V3 design as well as the parasitic resistances and minimum local ideality factors from the fitting. Figure S12 shows a photo of the cell. When results from Figures 3 and 4 are compared, it is apparent that the introduction of a metal grid to the 16 cm2 cell is effective in reducing the RS by more than 50% and the minimum local ideality factor to a value below that of the 5.8 cm2 gridless cell and the 16 cm2 gridless cell. The encapsulated 16 cm2 was certified by Newport, confirming an impressive PCE at 12.1% (Figure S13). A certified JSC of 17.3 mA/cm2 and a FF of 61.9% is achieved for this cell. In particular, a very high VOC of 1.13 V is maintained for this 16 cm2 cell. This is the highest certified efficiency for a perovskite device larger than 10 cm2 at the cell level rather than at the module level. Tables S5−8 summarize the electrical characteristics of cells fabricated in this work measured at the University of New South Wales showing relative reliability of our in-house measurement. It is expected that improvements in metal grid design will further reduce RS and therefore improve performance for these large cells in future work (Figure S14 and Table S8). The large cells fabricated by the SAS in this work when encapsulated have sufficient stability for independent certifications. Results in Figure S15 show that the 16 cm2 cell is stable after 2 months of storage in ambient conditions. A short movie in the Supporting Information shows the ability of the 2 month old certified 16 cm2 cell in powering a fan. The good stability of the large device is likely to be due to the smaller perimeter to area ratio (1 cm−1 for 16 cm2 device as opposed to 3.8 cm−1 for 1.2 cm2 device) with less exposure to the ambient including possible moisture ingress at the edges of the device. We remeasured the 16 cm2 cell 5 months after fabrication (Figure S16). The cell’s maximum power point (∼0.76 V) current density stabilizes within seconds at ∼16 mA cm−2, resulting in a PCE of 12%. To conclude, we have developed an antisolvent spraying process, which allows high-quality perovskite film to be fabricated over a large area. The advantages of SAS method compared to the conventional antisolvent dropping method include less antisolvent usage, rapid delivery of the antisolvent, faster rate of supersaturation, denser nucleation, and greater 1982

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(7) Yang, M.; Zhou, Y.; Zeng, Y.; Jiang, C. S.; Padture, N. P.; Zhu, K. Square−centimeter solution−processed planar CH3NH3PbI3 perovskite solar cells with efficiency exceeding 15%. Adv. Mater. 2015, 27, 6363−6370. (8) Chen, W.; Wu, Y.; Yue, Y.; Liu, J.; Zhang, W.; Yang, X.; Chen, H.; Bi, E.; Ashraful, I.; Grätzel, M.; et al. Efficient and stable large-area perovskite solar cells with inorganic charge extraction layers. Science 2015, 350, 944−948. (9) Bi, D.; Yi, C.; Luo, J.; Décoppet, J.-D.; Zhang, F.; Zakeeruddin, S. M.; Li, X.; Hagfeldt, A.; Grätzel, M. Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%. Nat. Energy 2016, 1, 16142. (10) Jeon, N. J.; Noh, J. H.; Kim, Y. C.; Yang, W. S.; Ryu, S.; Seok, S. I. Solvent engineering for high-performance inorganic−organic hybrid perovskite solar cells. Nat. Mater. 2014, 13, 897−903. (11) Yang, W. S.; Noh, J. H.; Jeon, N. J.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. High-performance photovoltaic perovskite layers fabricated through intramolecular exchange. Science 2015, 348, 1234−1237. (12) Kim, J.; Yun, J. S.; Wen, X.; Soufiani, A. M.; Lau, C.-F. J.; Wilkinson, B.; Seidel, J.; Green, M. A.; Huang, S.; Ho-Baillie, A. W.-Y. Nucleation and growth control of HC (NH2)2PbI3 for planar perovskite solar cell. J. Phys. Chem. C 2016, 120, 11262. (13) Razza, S.; Di Giacomo, F.; Matteocci, F.; Cina, L.; Palma, A. L.; Casaluci, S.; Cameron, P.; D’epifanio, A.; Licoccia, S.; Reale, A.; et al. Perovskite solar cells and large area modules (100 cm2) based on an air flow-assisted PbI2 blade coating deposition process. J. Power Sources 2015, 277, 286−291. (14) Deng, Y.; Dong, Q.; Bi, C.; Yuan, Y.; Huang, J. Air−stable, efficient mixed−cation perovskite solar cells with Cu electrode by scalable fabrication of active layer. Adv. Energy Mater. 2016, 6, 1600372. (15) Kim, J. H.; Williams, S. T.; Cho, N.; Chueh, C. C.; Jen, A. K. Y. Enhanced environmental stability of planar heterojunction perovskite solar cells based on blade−coating. Adv. Energy Mater. 2015, 5, 1401229. (16) Hwang, K.; Jung, Y. S.; Heo, Y. J.; Scholes, F. H.; Watkins, S. E.; Subbiah, J.; Jones, D. J.; Kim, D. Y.; Vak, D. Toward large scale roll− to−roll production of fully printed perovskite solar cells. Adv. Mater. 2015, 27, 1241−1247. (17) Li, Y. W.; Meng, L.; Yang, Y.; Xu, G. Y.; Hong, Z. R.; Chen, Q.; You, J. B.; Li, G.; Yang, Y.; Li, Y. F. High-efficiency robust perovskite solar cells on ultrathin flexible substrates. Nat. Commun. 2016, 7, 10214. (18) Lau, C. F. J.; Deng, X.; Ma, Q.; Zheng, J.; Yun, J. S.; Green, M. A.; Huang, S.; Ho-Baillie, A. W. Y. CsPbIBr2 perovskite solar cell by spray-assisted deposition. ACS Energy Lett. 2016, 1, 573−577. (19) Barrows, A. T.; Pearson, A. J.; Kwak, C. K.; Dunbar, A. D.; Buckley, A. R.; Lidzey, D. G. Efficient planar heterojunction mixedhalide perovskite solar cells deposited via spray-deposition. Energy Environ. Sci. 2014, 7, 2944−2950. (20) Tait, J.; Manghooli, S.; Qiu, W.; Rakocevic, L.; Kootstra, L.; Jaysankar, M.; de la Huerta, C. M.; Paetzold, U.; Gehlhaar, R.; Cheyns, D. Rapid composition screening for perovskite photovoltaics via concurrently pumped ultrasonic spray coating. J. Mater. Chem. A 2016, 4, 3792−3797. (21) Das, S.; Yang, B.; Gu, G.; Joshi, P. C.; Ivanov, I. N.; Rouleau, C. M.; Aytug, T.; Geohegan, D. B.; Xiao, K. High-performance flexible perovskite solar cells by using a combination of ultrasonic spraycoating and low thermal budget photonic curing. ACS Photonics 2015, 2, 680−686. (22) Mao, L.; Chen, Q.; Li, Y. W.; Li, Y.; Cai, J. H.; Su, W. M.; Bai, S.; Jin, Y. Z.; Ma, C. Q.; Cui, Z.; et al. Flexible silver grid/PEDOT:PSS hybrid electrodes for large area inverted polymer solar cells. Nano Energy 2014, 10, 259−267. (23) Zhang, M.; Yun, J. S.; Ma, Q.; Zheng, J.; Lau, C. F. J.; Deng, X.; Kim, J.; Kim, D.; Seidel, J.; Green, M. A.; et al. A. W. Y. High-efficiency rubidium-incorporated perovskite solar cells by gas quenching. ACS Energy Lett. 2017, 2, 438−444.

uniformity over a large area. Time-resolved PL measurement and EL/PL imaging also confirm better film quality for better electrical properties such as interfacial series resistance and lower effective dark saturation current in the device fabricated by the SAS method. A semidistributed diode model is used to optimize grid design without computational complexity and good accuracy with a trade-off between the series resistance from the FTO/metal grid and the shading loss from the metal grid. Through the inclusion of a metal grid, we have successfully demonstrated a 16 cm2 perovskite device at the cell level with a certified highest efficiency at 12.1%.



ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsenergylett.7b00573. Materials preparation, sample fabrication, characterization method, and additional data (PDF) UNSW perovskite solar cell with fan (AVI)



AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Phone: +61 2 9385 4257. *E-mail: [email protected]. Phone: +61 2 9385 4257. ORCID

Meng Zhang: 0000-0002-1004-5662 Martin A. Green: 0000-0002-8860-396X Anita W. Y. Ho-Baillie: 0000-0001-9849-4755 Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS The Australian Centre for Advanced Photovoltaics (ACAP) encompasses the Australian-based activities of the Australia U.S. Institute for Advanced Photovoltaics (AUSIAPV) and is supported by the Australian Government through the Australian Renewable Energy Agency (ARENA). We thank the Analytical Centre at UNSW for their technical support.



REFERENCES

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DOI: 10.1021/acsenergylett.7b00573 ACS Energy Lett. 2017, 2, 1978−1984

Letter

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1984

DOI: 10.1021/acsenergylett.7b00573 ACS Energy Lett. 2017, 2, 1978−1984