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Cite This: J. Phys. Chem. Lett. 2018, 9, 4326−4335

Perovskite Solar Cells: Toward Industrial-Scale Methods Yulia Galagan*

J. Phys. Chem. Lett. 2018.9:4326-4335. Downloaded from pubs.acs.org by UNIV OF TOLEDO on 08/12/18. For personal use only.

TNO − Solliance, High Tech Campus 21, Eindhoven 5656AE, The Netherlands ABSTRACT: Research progress in hybrid perovskite solar cells has increased enormously over the last years, making perovskites very promising candidates for future PV technologies. Perovskite solar cells use abundant and low-cost starting materials, providing economic advantages for large-scale implementation. A transition from laboratory-scale fabrication to industrial manufacturing requires scaling up of the dimension of the devices; manufacturing of large-area modules, considering the development of interconnection as an important step toward upscaling; and development of deposition methods alternative to spin coating, which are industrially compatible and facilitate high power conversion efficiency of the manufactured devices. This Perspective provides an overview of the recent developments toward industrial-scale manufacturing. Advances and perspectives in the developments of sheet-to-sheet and roll-to-roll deposition methods are discussed along with other related technologies required for industrial-scale methods, e.g., laser ablation, drying, post-treatment, and the use of alternative industry-compatible solvents for manufacturing of perovskite solar cells. sheet resistance of the TCO electrode of 10 Ω/□ (a typical value for TCO on glass) have maximum performance with a subcell width of 5 mm (see Figure 1e). However, modules produced on plastic substrates where the sheet resistance of the transparent electrode is 60 Ω/□ demonstrate an optimal subcell width of 3 mm. These results are in line with the simulation performed by Jaysankar et al.12 Interestingly, the smaller subcell width was found to be not beneficial for the PCE of the module because it resulted in an increasing number of interconnections (dead area), lowering the current density of the module. This was observed because the number of interconnections increased, thereby decreasing the active area. A geometrical fill factor (GFF), the ratio of the active area in the module to the aperture area, is affected not only by the number of interconnections but also by their width. Thus, Moon et al.13 made calculations of relative power losses with increasing width dead area (Wd) for the PV modules with a Jsc of 19.6 mA/cm2, Voc of 1.1 V, FF of 74%, and TCO sheet resistance of 15 Ω/□. The results, depicted in Figure 2a, clearly point out that with decreasing dead area width Wd from 3000 to 500 μm the overall loss decreases dramatically from about 35% down to about 10% at a fixed Wa of around 6 mm. The research reveals the importance of having very narrow interconnections in the modules and a high GFF in order to obtain high PCEs. This is still a challenging task in the field of perovskite photovoltaics, but a lot of research in this area is ongoing. There are a lot of publications where interconnections are realized using mechanical scribes for P2 and P3 scribes.14 The dead area using this method can be quite small, resulting in a

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apid progress in the development of perovskite-based solar cells (PSCs) has been demonstrated in the past few years. With a record power conversion efficiency (PCE) of 22.7%,1 PSC technologies can compete with conventional photovoltaic (PV) technologies. Owing to the very attractive features of tunable absorption spectra and very low nonradiative recombination, PSCs have a big potential for future applications. Although some issues of stability and toxicity still have to be addressed before commercialization of PSC technologies, big progress has been made in these areas.2−7 In order to facilitate a transition from laboratory-scale fabrication toward industrial manufacturing, development of deposition methods alternative to spin coating is of high demand.8,9 The alternative industry-compatible deposition methods should provide high layer uniformity with large crystals and fewer grain boundaries over the large area, thereby ensuring high PCEs of the manufactured devices. Apart from the uniformity and the morphology of perovskite layers over a large area, the efficiency of the devices might change with scaling up of the dimension of the cells. For example, as has been shown by Yang et al.,10 increasing the cell dimension from 0.12 cm2 to 1.1 cm2 results in a PCE drop from 17.5 to 15.5%. The efficiency dropped mainly due to a decrease in the fill factor (FF), which was affected by the resistance of transparent conductive oxide (TCO) electrodes. In order to quantify the losses in large-area PSCs and modules, Galagan et al.11 performed a simulation of the current distribution on the devices. The performed simulation reveals the correlations between the dimension of the cells, their PCEs, and the sheet resistance of the electrodes (see Figure 1a−c). Moreover, a simulated current distribution in the modules with different widths of the subcell (W) (see Figure, 1d) helped to determine the optimal width of the subcells in the modules. The results demonstrate that modules with the © 2018 American Chemical Society

Received: April 29, 2018 Accepted: July 13, 2018 Published: July 19, 2018 4326

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Figure 1. (a,b) Simulated J−V curves of the PSCs with areas of 0.03, 0.16, 0.36, and 1 cm2 and different sheet resistances of TCO of (a) 10, (b) 40, and (c) 60 Ω/□. (d) Schematic illustration of the module design. (e) Simulated maximum power in the perovskite modules with a varied width of the subcells and different sheet resistances of the TCO electrodes. Adapted from ref 11 with permission from The Royal Society of Chemistry.

Figure 2. Calculated relative power losses as a function of the width of the active area (Wa) and the width of the dead area (Wd).13 Microscope images of P1, P2, and P3 scribes with dead areas of (b) 38720 and (c) 250 μm.23 (a) Reproduced from ref 13 with permission, Copyright 2015 IEEE. (b) Reproduced from ref 20 with permission, Copyright 2017 IEEE. (c) Reproduced from ref 23 with permission, Copyright 2017 Elsevier B.V.

high GFF, e.g., 87.3% as reported by Yang et al.14 or 91% reported Qiu et al.15 However, the bottleneck of this

technology is that the TiO2 electron-transport layer (ETL), a very dense material, remains in the interconnection between 4327

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subcells after the mechanical scribe.14 It significantly affects the module’s performance: a thick layer of TiO2 will lead to low FF, thereby requiring a very thin layer for a high PCE. The most promising technology to achieve a high GFF in the modules is laser ablation. Patterning and manufacturing of

solution-processing. There are a number of reports where the doctor blade technique was used for deposition of a perovskite photoactive layer14,30−35 as well as for the deposition of all other functional layers in the devices.33 Large-area modules were also produced by many groups using doctor blade methods. Thus, Razza et al.36 reported the manufacturing of blade-coated PSCs with efficiencies up to 13.3%, while the 10.1 cm2 modules demonstrated a PCE of 10.4% and modules with an area of 100 cm2 had a PCE of 4.3%. Gardner et al.37 presented PSC modules with active areas of 4 cm2 blade coated using nonhazardous solvent systems; the modules demonstrated efficiencies of 11.9% (from IV scans) and 8.2% (from maximum power point tracking). Further optimization, in order to reduce resistive and optical loses, allowed Imec to produce blade-coated modules with an area of 16 cm2, fabricated either by laser patterning or mechanical scribing.38 These modules (see Figure 3d) demonstrate up to 12.5% aperture area efficiency. To manufacture efficient modules using the doctor blading technique, several groups have demonstrated the importance of substrate temperature for homogeneous growth of the perovskite crystals, which is responsible for the high efficiency of the devices.39,40

The most promising technology to achieve a high GFF in the modules is laser ablation. the modules with the help of a laser not only minimize the dead zone16−18 but also enable selective ablation with complete removal of the materials without damaging the underneath layer. Rakocevic et al.19 performed a comparison between two methods of patterning for fabrication of perovskite modules. Mechanical scribing and lather ablation were employed for manufacturing of the modules with an aperture area of 4 cm2. Using both methods, a GFF of 94% was achieved, and the fabricated modules demonstrated aperture area efficiencies of 15%. Another report on fully laserprocessed large-area (14.5 cm2) perovskite modules with a GFF of 95% (Figure 2b) and a PCE of 9.3% were presented by Palma et al.20 Later, this research group demonstrated flexible perovskite modules of 12 cm2 with an active area efficiency of 8.8%, and the modules were manufactured using laser ablation technologies.21 Solliance demonstrated the use of laser technologies for both glass-based22,23 and flexible modules,24 where the GFF reached 95% (Figure 2c), with a record PCE for 6 in. modules of 14.5 and 10.1% for glass-based and flexible modules, respectively.

Substrate temperature is important for homogeneous growth of the perovskite crystals. Fabrication of a perovskite layer using spray coating was demonstrated by Das et al.;41 the deposition was performed in a single step and resulted in high uniformity of the perovskite film. Adaptation of spray coating for two-step deposition of the perovskite layer was realized by Chai et al.42 and Huang at al.43 Furthermore, Bi et al.44 utilized spray deposition of perovskites with a controlled temperature of the substrate to facilitate rapid solvent evaporation, which is essential for avoiding dendritic crystals and obtaining dense perovskite thin films without pinholes. Spray-coated multilayer PSCs with an active area of 1.5 cm2 have been reported by Bishop et al.,45 where spray coating was adapted for sequential deposition of four layers in the device stacks. Another example of the PSCs with three spray-coated layers was reported by Mohamad et al.,46 where PEDOT:PSS, perovskites and PCBM layers were spray coated. Tait et al.47 further exploited manufacturing of the modules, demonstrating initial PCEs of 15.7% for small-scale devices and 11.7% for 3.8 cm2 modules. Reports on spray coating of multiple layers in perovskite devices with PCEs comparable to those of the devices produced using spin coating confirmed the suitability of spray coating for manufacturing of large-area efficient perovskite modules.48 Although a lot of different deposition techniques were explored for the manufacturing of PSCs and modules, slot-die coating remains one of the most investigated and, perhaps, the most preferred deposition methods. Scientists from SPECIFIC49 exploited a slot-die coating technique for infiltration of perovskites into a mesoporous titania scaffold. A perovskite crystallization process was controlled by the temperature of the substrate and by applying a rapid postprocess using an air knife. The use of slot-die coating was also reported by Lee et al.50 Modules with an active area of 10 cm2 were fabricated using mixed lead precursors of PbAc2 and PbCl2 and employing a nitrogen gas blower. The PCE of these modules reached 8.3%. Furthermore, using a Mini Roll coater, Ciro et

Development of industry-compatible deposition methods has experienced rapid progress. Manufacturing of large-area modules implies the development of industrial-scale methods for deposition of all layers. Although large-area modules were first produced using a spin coating and mechanical scribe25 (Figure 3a), development of industry-compatible deposition methods experienced rapid progress. The first demonstration of scalable PSC manufacturing is based on successful experience in organic solar cells (OPVs) and dye-synthesized solar cell (DSSC) manufacturing. For example, screen printing of mesoscopic TiO2 and Al2O3 materials for manufacturing of PSCs is adapted from DSSC technologies.26,27 Then, screen printing was further utilized by different research groups28,29 for manufacturing of triplelayered mesoscopic perovskite modules. Thus, large-area (10 × 10 cm2) printable mesoscopic perovskite modules were demonstrated by Priyadarshi et al.28 (Figure 3b) and Hu et al.29 (Figure 3c). The modules exhibited efficiencies exceeding 10% and were fabricated using screen-printed processes along with infiltration of the perovskite solution. However, manufacturing other stacks than mesoscopic ones requires the development of a scalable deposition process for all layers including the perovskite. Scalable deposition of perovskite layers began by using doctor blade coating as an alternative to spin coating. Although doctor blading is not a fully roll-to-roll (R2R)-compatible method, it is widely used in industry for batch-based sheet-tosheet (S2S) deposition because of low-cost and simplicity for 4328

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Figure 3. (a) Perovskite-based PV module with an active area of 13.5 cm2 and stabilized PCE of 10.1%, fabricated by spin coating and a mechanical scribe,25 reproduced from ref 25 with permission. (b) Monolithic perovskite modules with a size of 10 × 10 cm2 (active area = 70 cm2) with a PCE of 10.74%, fabricated using a screen printing process along with infiltration of the perovskite solution,28 reproduced from ref 28 with permission, Copyright 2016 The Royal Society of Chemistry. (c) Perovskite PV module with 10 serially connected cells (10 × 10 cm2) with a PCE of 10.4% on an active area of 49 cm2,29 reproduced from ref 29 with permission, Copyright 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (d) Perovskite PV module with a graphene interface demonstrating a PCE of 12.5% over a 50 cm2 active area, reprinted with permission from ref 54, Copyright 2017 American Chemical Society. (e) Perovskite PV module with an aperture area of 36.1 cm2 and a certified PCE of 12.1%,55 reproduced from ref 55 with permission, Copyright 2017 Macmillan Publishers Limited, part of Springer Nature. (f) A 15 × 15 cm2 slot-die-coated perovskite PV module with an aperture area of 168.75 cm2, containing 25 interconnected cells,23 reproduced from ref 23 with permission, Copyright 2017 Elsevier B.V.

al.51 investigated slot-die coating deposition for fabrication of PSCs in ambient conditions. The same as those for other deposition methods, the results point out that the morphology of the layer strongly depends on the processing temperature. A fully ambient roll processing of flexible PSCs was demonstrated by Krebs et al.52 The slot-die-coated devices with printed back electrodes exhibited a PCE of 4.9%, while spin-coated devices with evaporated electrodes yielded a PCE of 9.4%. Performed research emphasizes that the morphology of the perovskite layers strongly depends on the surface properties of the layer underneath. Therefore, in order to modify the surface properties, Gu et al.53 reported deposition of a self-assembled monolayer onto PEDOT:PSS prior to the deposition of perovskite. It modifies the crystallinity and uniformity of the perovskite layer, resulting in improving the PCE from 3.7 to 5.1%. The importance of interfaces for fabrication of large-area modules was also noticed by Agresti et al.54 It was reported that two-dimensional (2D) materials such as graphene can tune the interfacial properties of PSCs. The possibility of processing graphene from solution allowed the manufacturing of large- area modules with an active area of 50.6 cm2 and a PCE of 12.6% (see Figure 3d). In order to fabricate a large-area uniform layer, Weihua Solar applied a gas pumping process after the slot-die coating of a perovskite layer. Then, te carbon back electrode was screen-

Slot-die coating remains one of the most investigated and, perhaps, the most preferred deposition methods. printed on top of the fabricated perovskite layer. Manufacturing of the modules was competed by laser scribing in order to make series interconnection. These technologies allowed manufacturing of the perovskite modules the areas of 5 × 5 cm2 and a PCE of 10.6%. The technology was further scaled up, and modules with the dimension of 45 × 65 cm2 were fabricated.56 Uniform layer formation over the large area is the most challenging task in the upscaling of perovskites, which was solved by Weihua Solar using the gas pumping method. To control the formation of a large-area perovskite film, Gao et al.57 introduce the air knife method with multiple gas flows, which allows fast drying of the film, providing high uniformity over the large area. Further, Chen et al.55 proposed a new deposition route for perovskite film formation that does not rely on the use of solvent quenching or vacuum posttreatments but is based on the rapid conversion of amine complex precursors to perovskite films using a pressure application step. The new deposition approach was performed 4329

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Figure 4. R2R production of PSCs demonstrating (a) conversion of the cloudy PbI2 layer into a perovskite film and (b) a flexible PSC module on a 10 × 10 cm2 substrate with five cells serially interconnected.59 (a,b) Reproduced from ref 59 with permission, Copyright 2015 WILEY-VCH Verlag GmbH & Co. KGaA. (c) Perovskite layer slot-die coated on Solliance’s R2R line, reproduced from ref 64 with permission, Copyright 2017 Solliance. (d) R2R-produced flexible perovskite PV module with 36 serially interconnected subcells, an aperture area of 160 cm2, and a PCE of 10.1%, reproduced from ref 24 with permission, Copyright 2017 Solliance.

Focusing on the scalable industry-compatible manufacturing of large-area PSC modules, Solliance reached several remarkable milestones. Using the S2S slot-die coating method, perovskite modules with an aperture area of 168 cm2 with a PCE of 10% were demonstrated23 (Figure 3f). These results were later improved, reaching a PCE of 13.75% (14.5% active area efficiency).22 The modules contained 24 serially connected subcells produced through P1, P2, and P3 laser interconnection technologies. Obtained results were farther exploited by Solliance toward scalability using R2R slot-die coating technologies. R2R coating, drying, and annealing of the perovskite and other layers were performed at ambient conditions with a web speed of 5 m/min (Figure 4c). Developed technologies allowed one to demonstrate a world record PCE of 13.5% for PSCs using R2R manufacturing;24 this result is an improved version of the earlier reported PCE of 12.3%.24 Furthermore, the series of modules with aperture areas of 4, 10.5, and 160 cm2 were manufactured using R2R coating technologies. Modules of both 4 and 10.5 cm2 with a GFF of 93% yielded a PCE of 12.2% (13.5% active area efficiency), indicating no efficiency loses when going upscale from small devices to modules. Further scaling up of the module dimension to 160 cm2 resulted in a PCE of 10.1% (11.1% active area efficiency); the module is shown in Figure 4d. The results prove the capability of the high-volume production for perovskite PV technologies using low-temperature processes (below 120 °C), low-cost materials, and nontoxic solvents suitable for industrial-scale manufacturing.

in air at low temperature and resulted in a pinhole-free and highly uniform perovskite layer, facilitating fabrication of largearea perovskite modules (Figure 3e) with an aperture area of 6 × 6 cm2 and certified efficiency of 12.1%. The adaptation of a 3D printing slot-die coater for deposition of PSCs was realized by researchers from Australia and Korea.58 A modified 3D printer was used to develop the printing process for potential use in large-scale R2R production, where PSCs with PCEs of 11.6% were demonstrated. Later, the same group demonstrated fully printed PSCs using slot-die coating, where sequential slot-die coating processes were developed to produce efficient PSCs. The devices where all layers, except the electrodes, were coated demonstrate PCEs of up to 11.96%59,60 (see Figure 4a,b). Then, Kim et al.61 combined slot-die coating with a blowing step; this significantly improved the quality of perovskite layer. Further improvement was achieved by optimizing the temperature of the deposition, and the manufactured devices demonstrated a PCE of 12.7%. These results were further improved in the fully slot-die-coated devices62 based on a Bifluo-OMeTAD hole-transport layer (HTL) with a PCE of 14.7%. Blowing-assisted deposition was further explored to manufacture devices using modified PEDOT:PSS as the HTL, which resulted in a maximum PCE of 19.48%.63 This technology and an optimized formulation then were successfully transferred to the slot-die coating on glass and subsequently to R2R on flexible substrates, resulting in maximum PCEs of 15.57 and 11.16%, respectively. 4330

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devices.73 Furthermore, an additional parameter influencing the stability of the modules, which does not play a role in the stability of the signed cells, is an interconnection. The

The importance of a solvent system for fabrication of perovskite films is well accepted. The solvent systems along

The importance of a solvent system for fabrication of perovskite films is well accepted.

The influence of the interconnections on the stability of the modules still needs to be investigated.

with the selected deposition method, quenching, and drying are responsible for the nucleation, crystallization, and film formation. The most commonly used solvents for perovskite precursor deposition are g-butyrolactone (GBL),37 N,Ndimethylformamide (DMF),65,66 or their mixtures with dimethyl sulfoxide (DMSO).65,67 Unfortunately, with considerable achievements in terms of PCEs using DMF, this solvent is highly toxic and therefore unsuitable for industrial-scale manufacturing.68 The alternative solvent system, designed for rapid crystallization of the CH3NH3PbI3 at room temperature, is based on methylamine and acetonitrile.69 These solvents are nontoxic; however, their use is limited by their high flammability and volatility. High PCEs can be obtained in PSCs made from mixtures of nontoxic GBL and DMSO,37 but GBL is classified as a psychoactive drug and has a restriction for use in many countries. DMSO remains the only nonhazardous solvent suitable for industrial use.70 However, PSCs produced solely from DMSO have low PCEs due to very small grains size and a high number of pinholes in the layer.71 Mixing DMSO with cosolvents, such as 2-methylpyrazine (2MB) and 1-pentanol (1-P), helps in rapid nucleation and crystallization of the perovskite phase in the deposited layer.71 High PCEs of the devices confirm that the developed solvent system of DMSO/2-MP/1-P is highly suitable for R2R manufacturing of PSCs. Apart from the nonhazardous solvents for perovskite deposition, industry-scale manufacturing will require nontoxic solvents for all other processes. Highly toxic solvents such as toluene or chlorobenzene are still widely used for the deposition of charge transporter materials, e.g., spiroOMeTAD or PCBM, or in the antisolvent step. Replacement of these solvents by greener alternatives was reported by Yavari et al.;72 it was shown that anisole used both as an antisolvent and a solvent for spiro-OMeTAD leads to comparable PCEs when using toxic modifications. Despite significant progress in the technologies for the upscaling of PSCs, the stability of the modules still needs detailed investigation. A lot of research has been focused on understanding the degradation mechanism in PSCs73−75 and designing stable devices.76 It was shown that introduction of the alkali metal cation, e.g., cesium or rubidium,77,78 improves the stability of the PSCs. A positive effect on the stability has also been achieved by 2D/3D interface engineering76,79 as it is well accepted that the key point of the PSC’s stability lies at interfaces.80 Furthermore, the effect of transport layers (ETL and HTL) on the stability of the PSC is widely presented in the literature,81 concluding that inorganic transport materials might be preferred to maintain a long lifetime of the PSCs.82,83 However, demonstration of stable devices on a lab scale does not yet guarantee the stability of the modules. One of the additional parameters that is responsible for the stability of the modules, as discussed earlier, is layer uniformity over the large area. Fabrication of uniform pinhole-free and crack-free layers is essential for the stability of large-area modules.7 Defects in the layers, as well as nonoptimized interfaces, introduce recombination centers, leading to nonradiative losses in the

influence of the interconnections on the stability of the modules still needs to be investigated. For example, incomplete removal of the ETL (in n−i−p configuration) or HTL (in p− i−n configuration) in the P2 scribe not only affects the performance of the modules14 but also affects their stability. Furthermore, the P2 scribe (see Figure 1c) aimed to remove photoactive perovskite layer, and the ETL and HTL allow direct contact of the top electrode (which is typically metal) with the perovskite material. Although the issues related to such contact are not yet widely discussed in the literature, it is expected to have a very strong influence on the long-term stability of the modules due to ion exchange between the perovskites and the electrode material, e.g., Au or Al. It is wellknown from the literature84,85 that any contact between the metal electrode and the perovskite will result in the formation of a nonconductive metal halide and introduce an iodide deficiency within the perovskite. To overcome this issue, several research groups employed Cr/Au84 or Cu86 contacts, which slow down the interaction, but this concept was not yet employed on a module level. Another approach to solve this issue was the use of a carbon electrode. Thus, stable carbonbased modules with an active area of 70 cm2 with a PCE of 10.74% were demonstrated by Priyadarshi et al.;28 the modules demonstrate an ambient stability of more than 2000 h with less than a 5% reduction in efficiency. Hu et al.29 demonstrated a mesoscopic module with a carbon electrode. The 10 × 10 cm2 module shows an active area efficiency of 10.4%. The lightsoaking stability of this module exceeds 1000 h, the outdoor stability was confirmed to be at least 1 month, and a shelf lifetime of more than 1 year has been proven. Another alternative for the highly reactive back contacts is an ITO electrode, which is less reactive than the perovskite, resulting in very stable bifacial devices.87 Finally, apart from intrinsic and operational stability, development of a reliable encapsulation strategy for PSCs and modules88 is another key point to guarantee a long lifetime of the modules for future commercial applications.

Nonhazardous industrial solvent systems, large-area deposition, uniform drying, laser ablation, and encapsulation technologies will enable industrial-scale manufacturing. Nonhazardous industrial solvent systems, large area deposition, uniform drying, laser ablation, and encapsulation technologies will enable industrial-scale manufacturing of PSCs modules. Several examples of building perovskite solar plants or large-area panels have already been demonstrated, showing the feasibility of perovskite PV technologies. Thus, the 4331

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Figure 5. (a) The 7 m2 perovskite solar panels with a screen-printed triple layer mesoporous scaffold and infiltrated by a mixed cation lead halide perovskite, reproduced from ref 29 with permission, Copyright 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (b,c) Power station set up at Weihua Solar containing 32 slot-die-coated perovskite panels of 45 × 65 cm2, reproduced from ref 56 with permission, Copyrigt 2017 Chinese Institute of Electronics.

ORCID

Huazhong University of Science and Technology, along with demonstrating stable and 10% efficient 10 × 10 cm2 perovskite modules,29 also showed fully printable large-area 7 m 2 perovskite panels (see Figure 5a). This achievement proves the suitability of screen printing for manufacturing of perovskite PV modules. Furthermore, a technology used by Weihua Solar56 for printing 10.6% efficient 5 × 5 cm2 modules was exploited further for manufacturing large-area 45 × 65 cm2 modules, allowing one to set up a power station made of 32 perovskite panels (see Figure 5b,c). This achievement demonstrates significant progress in the field of scaling up perovskite technologies and bringing them toward industrial manufacturing. Although several challenging issues such as stability, toxicity, etc. still need to be solved before commercialization of these technologies,73 there are several companies who believe in the bright future of PSCs. Along with materials providers, such us Tokyo Chemical Industry (TCI),89 FrontMaterials,90 and GreatCell Solar,91 there are several developers of solar panels based on perovskite materials: Oxford PV,92 Microquanta Semiconductor,93 Saule Technologies,94 Frontier Energy Solution,95 Toshiba,96 and Solaronix.97 Involvement of industry in technology development at an early stage ensures a fast transition from laboratoryscale fabrication toward industrial-scale manufacturing and will allow rapid commercialization of perovskite-based PV technologies.



Yulia Galagan: 0000-0002-3637-5459 Notes

The author declares no competing financial interest. Biography Yulia Galagan is a Senior Scientist at Holst Centre/TNO and Solliance. She received her Ph.D. in chemistry in 2002 from Kyiv University. She was a postdoctoral researcher at National Taiwan University, and in 2008, she joined Holst Centre. Her research interests are focused on organic and perovskite-based electronics and scaling up the emerging technologies. Currently, Yulia Galagan is a group leader responsible for large-area processing and development of technologies for roll-to-roll manufacturing of perovskite photovoltaics.



ACKNOWLEDGMENTS This work was supported by the European Commission’s StableNextSol COST Action MP1307. The work has been supported by Solliance, a partnership of R&D organizations from The Netherlands, Belgium, and Germany working in thin-film photovoltaic solar energy. This work is part of the research programme CLEARPV, Grant M-ERA.NET 2017 CW with Project Number 732.017.105, which is (partly) financed by The Netherlands Organisation for Scientific Research (NWO).



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REFERENCES

(1) NREL Best Research Cell Efficiencies. https://www.nrel.gov/pv/ assets/images/efficiency-chart.png (2018).

*E-mail: [email protected]. 4332

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