Metal Oxides: Paving the Way to Perovskite Cells

ENGR0011/0711 Section Group # Disclaimer — This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly available information and may not be provide complete analyses of all relevant data. If this paper is used for any purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk.

METAL OXIDES: PAVING THE WAY TO PEROVSKITE CELLS

Desmond Zheng, [email protected], Sanchez 10:00, Patrick Flaherty, [email protected], Vidic 2:00

Abstract —With the imminent decline of fossil fuels, a [2]. This dilemma does not currently allow perovskite to new clean form of energy is emerging to take its place at be a sustainable marketable solar cell. Research of the apex of the energy industry: solar power. Enormous possible solutions has been conducted for the unique strides in the research of solar panel production have compound of perovskite in solar cells. resulted in a product with higher levels of efficiency and Prior to its use in solar cells, perovskite had no major lower costs than ever before: perovskite solar cells. While significance as a component of modern technology. As a exploring the background of this rapidly developing solar material, perovskite possesses a structure of ABX3, which cell, we analyzed a main obstacle to the mass production Muhammad Ahmed, a researcher at the National of perovskite solar cells in great detail: excessive University of Sciences and Technology in Islamabad, exposure to moisture in the environment. Despite being a Pakistan, describes in the scientific journal, International revolutionary new form of solar cells, perovskite solar Journal of Photoenergy, by writing that “ABX3 describes cells must overcome this roadblock to be mass produced. the crystal structure of perovskite class of materials, Perovskite solar cells can be a pivotal part of the where A and B are cations and X is an anion of different future once the issue of degradation is overcome. The dimensions with A being larger than X [3].” This is the main solution currently being researched is the use of a first time that this crystal structure, in the form metal oxide coating, which can combat the problem of the CH3NH3PbI, has been introduced into the world of solar cells experiencing rapid degradation by preventing any power, and it is being met with remarkable success. contact with moisture in the air. When the metal oxide Shown in Figure 1 [4], perovskite’s crystalline coating is perfected, perovskite solar cells will be as structure is what sets it apart from other solar cell sustainable as they are efficient. Once this technology is materials. Materials that have this particular molecular fine-tuned, companies can capitalize on producing more structure are typically used for semiconductor, cost effective solar panels with greater efficiencies. This superconductor, and thermoelectric-based research, as paper will explore the use of a metal oxide coating on they contain key conducting properties. ABX3 perovskite solar cells to surmount their weakness to (perovskite) molecules are synthesized by solid-state moisture in the environment and enable them to reshape mixing of commonly found elements, or by drying the the landscape of sustainable energy generation across the solution of precursor salts [3]. These methods of globe. synthetization are not difficult to utilize on a massive scale. A main component of perovskite is lead, which is Key Words—Protective Coating, Metal Oxide, Moisture another key element as to why corporations could Degradation, Perovskite, Solar Cell, Solar Efficiency manufacture perovskite with ease [4]. The use of lead to synthesize validates that perovskite is a sustainable A FUTURE PREEMPTIVELY compound to accumulate or synthesize, as lead exists in large amounts around the world. The easier it is for a PEROVSKITE material to be synthesized or accumulated, the less the material will cost for the companies who try to As the usage of fossil fuels decline around the globe, manufacture it. This feature is vital for perovskite cells to renewable energies have emerged to take their place. A succeed. premier choice in today’s renewable energy market is solar power. Recently, a new form of solar technology has FIGURE 1 [4] materialized: perovskite solar cells. These cells, composed from perovskite, an organic-metal halide compound [1], possess staggering levels of efficiency and economical pricing; however, one fatal flaw in the perovskite compound has caused companies to be hesitant about mass production. In the open environment, water vapor or moisture from the air will cause perovskite in the cells to rapidly degrade and become essentially useless 1 ENGR0011/0711 Section Group # in the presence of ultraviolet radiation, oxygen, and water. Shown in Figure 2, perovskite, or CH3NH3PbI3, is separated into separate ions under ultraviolet radiation and then amongst contact with the water vapor, or H2O, is broken down completely into hydrogen iodide, or HI [3]. This molecule cannot be used in a photochemical reaction to draw electrons from sunlight. Further research on perovskite cells shows that a humidity level of fifty-five percent is sufficient to deteriorate perovskite [3]. As areas Cubic perovskite structure, where cation A is with higher levels of sunlight generally tend to contain CH3NH3, cation B is Pb, and the anion X is a halogen higher quantities of humidity, this problem cannot be (I). ignored or the use of perovskite cells will be restricted Prior to any mass production, all problems of around the world. perovskite solar cells must be solved. The primary problem of these cells, degradation from moisture, has FIGURE 2 [3] caused setbacks in this technology since its birth. Multiple solutions exist currently, but the most prominent solution available is to coat metal oxide, such as titanium oxide

(TiO2), onto the perovskite to seal the cell from outside exposure [3]. This solution has been met with relative success, but is nowhere near the caliber of quality a metal oxide coating would need to be to adequately protect perovskite and ensure its long-term sustainability. Another method that is currently being tested is a vapor- The chemical reactions responsible for degradation applied metal oxide coating that would protect the solar amongst contact with moisture cell. This method has been met with similar success to the TiO2 coating, but nonetheless, is a step in the right Another problem combatting the progress of direction for the future of perovskite solar cell technology perovskite is the presence of lead (Pb) in the compound. [5]. These coatings will be discussed in greater detail For perovskite to be a sustainable compound, it must meet later, but their success as an easily applicable solution is the ecological factor of sustainability: “meeting human crucial for the long term viability of perovskite solar cell needs without compromising health of ecosystems” [7]. technology. The main form of perovskite used currently is Perovskite solar cells are intended to change the CH3NH3PbI3, which contains lead, a toxic metal during all energy industry and how consumers use energy to power processes of manufacturing and deployment. Concerns their devices. Researchers from the Johannes Kepler raised over the environmental impact of the lead in University in Austria, have already implemented these perovskite can be neutralized [3]. Though the perovskite cells into next-generation technology such as autonomous uses lead as a main component of the compound, the main drones, exoskeletons, and robotics [1]. Perovskite cells component can be any material that follows the formula may not be ready for the present-day market, but they ABX3, where A and B are cations and X is an anion [3]. A provide a glimpse into the bright future. To understand solution to this environmental issue is the use of other the breakthrough and setbacks of perovskite, it is elements in its place as the B cation [3]. An element preeminent to examine the difficulties in laboratory and gaining traction to replace lead is tin (Sb), which lays in large-scale production of perovskite cells and the main the same group on the periodic table and thus, shares solutions to absolve these major issues. similar properties with lead. Tests have shown that tin forms a similar compound with a more ideal bandgap, PERILS OF PEROVSKITE which is key to electrical conductivity [4]. Further experimenting with various other types of elements could Perovskite solar cells hold tremendous potential in the prove a better and safer replacement to lead. industries of energy production and manufacturing. Perovskite must overcome environmental and Despite their increasing capacity, perovskite cells face a chemical issues before becoming a mainstay solar cell. To major dilemma when used outside a laboratory setting. do so, research must be conducted and possible solutions Without being enclosed in a vacuum, perovskite rapidly must be tested. Possible elements to replace lead and degrades from water vapor in the air. Currently, this is the neutralize any harmful effects on the environment have major obstacle preventing perovskite cells from being been produced and can only effectively work when mass produced and sold as the premier option in solar perovskite cells can survive contact with the outside power. Due to this important reason, moisture presents world. Subsequently, the main solution currently being itself as a perilous opponent to perovskite solar cells [6]. designed for moisture degradation is a metal oxide The battle between perovskite and water vapor can be coating, which be discussed in detail in the next section explained by a sequence of chemical reactions undertaken [2]. 2 ENGR0011/0711 Section Group # Titanium and zinc oxide are only two types of metal MEDDLING WITH METALS oxides currently being examined and tested on as possible coatings for perovskite solar cells. Countless other metal Perovskite solar cells can become major factors in the oxides exist and could be better solutions for the issue of solar industry, but are plagued by the issues of degradation [3]. Any assortment or combination of these degradation and nonoperation when exposed to the metal oxides may allow perovskite to become a smallest amounts of moisture. This flaw of perovskite is sustainable compound to use in solar cells. However, undermining the research and advancement of this before searching for a suitable coating, researchers must breakthrough solar cell, but can potentially be solved with prove the worthiness of a metal oxide coating as the best the use of a metal oxide coating. The goal of the metal solution for moisture dilapidation. To do so, scholars and oxide is to provide a transparent, waterproof barrier that scientists must implement these preliminary oxide will protect the cell from water vapor as much as possible compounds to produce effective results in perovskite while affecting the total efficiency of the perovskite cell cells. as little as possible [2]. Creating a viable, sustainable metal oxide coating would justify producing perovskite HOW WILL THIS COATING BE cells. This is a very promising solution to the major IMPLEMENTED? problem of perovskite cells, and now the specific types of coatings will be discussed. Implementing a metal oxide coating requires careful research of the compound being used, the chemistry Titanium Oxide amongst bonding, and the aftereffects against the environment. Universities, such as the University of A promising front runner being developed to cover California at Los Angeles [8] and Japan Institute for these solar cells is the compound, titanium oxide (TiO2). Chemical Research and Kyoto University [5], have begun This particular coating requires a spin-coating of TiO2 implementing metal oxides onto current perovskite solar that goes over the perovskite solar cell [3]. TiO2 has cell models. These preliminary tests could be the first shown success in laboratory experiments, but has not yet stepping stone into the future of energy production. reached the caliber needed for commercial use. These At the Japan Institute for Chemical Research with tests have shown that TiO2 has a very minute effect on the collaboration with Kyoto University, graduate students photoelectric excitement of perovskite, and could prove to alongside their professors have fabricated a metal oxide be a very effective sealant to keep the moisture in the air coating of TiO2 using a chemical bath deposition method away from the sensitive perovskite material. In addition, (CBD). Another method of coating a metal oxide layer is TiO2 is not a very difficult material to be applied to the using a spin-coating of TiO2, which deposits the oxide surface of perovskite solar cells [6]. The spin-coating with an acidic solution of titanium isopropoxide in method to apply TiO2 could be done on a large scale to ethanol. This is then heated to 500ºC, which requires cover these solar cells [6]. While TiO2 has proven an costly thermal equipment, preventing these types of metal effective coating, other metal oxides are currently being oxide coated perovskite cells to be cost-effective [5]. The researched as possible alternatives. researchers at the Japanese institute are developing the CBD method as a low-cost alternative. Zinc Oxide FIGURE 3 [5] Another potential metal oxide that could be used for coating perovskite solar cells is zinc oxide, or ZnO. The scientific journal, Nature Nanotechnology, says that “This ZnO nanoparticle ﬁlm exhibits a continuous and smooth surface with a roughness of <2 nm and a particle size of <10 nm” [8]. This statement effectively means that titanium oxide provides a smooth coating over a perovskite cell while the particles are miniscule, which allows more sunlight to come into contact with the perovskite. The ability to prevent degradation while leaving the high levels of efficiency intact is vital for the long-term sustainability and use of perovskite solar cells in industries and homes. While no research has been done A schematic of the perovskite cell during the CBD to support one versus the other, ZnO could be more process efficient at allowing sunlight to contact the perovskite, leading it to be a more economical solution as directly it Compared to the 500ºC of a spin-coating, a chemical allows more electricity to be produced [8]. bath deposition of metal oxides only requires 150ºC [5]. The lower temperature would lead to an easier and inexpensive manufacturing process. To begin the CBD 3 ENGR0011/0711 Section Group # process, the perovskite was laid on top of the TiO2 (or outside of the solar cell. This coating would serve as a TiOx in Figure 3), which had been treated in an aqueous waterproofing agent for the cell, as well as inhibiting the solution of titanium oxysulfate and hydrogen peroxide. cell's electrical efficiency as little as possible [8]. Once This compound was placed on an indium tin oxide to this problem is solved permanently, perovskite will be further sustain the titanium oxide. Gold placed on top of able to be mass-produced and will be able to enter the the compound was deposited in the hole transport layer, marketplace with an unstoppable force. spiro-OMeTAD, which allows electrodes to transfer from Perovskite solar cells have shown extremely high light to the perovskite cell [5]. The Japanese university promise, despite not being able to be exposed to water. collaboration succeeded in fabricating the perovskite solar The tests inside of the vacuum chamber demonstrate that cell with a TiO2 layer using the chemical bath deposition perovskite has extremely high potential to be effective as method. Data from this experiment estimated that power a solar material, but this technology will be absolutely conversion efficiency of this cell was almost the same as impractical until it can overcome its moisture degradation perovskite solar cells without an oxide coating [5]. With problem. Perovskite cells are typically hard to make and further research or communication with other researchers, test currently due to this problem. such as the University of California at Los Angeles, the efficiency levels of perovskite cells can be sustained at an Manufacturing Issues equivalent or superior level [8]. At the University of California at Los Angeles, Due to the dilapidation that occurs, the manufacturing researchers have created a different type of metal oxide of perovskite cells is a very expensive and difficult coating, using nickel oxide (NiOx) and zinc oxide (ZnO) process. Assuming that a long-term solution to this nanoparticles as an outside layer [8]. These nanoparticles problem is arrived at, steps would have to be made for the act as a hole and electron transport layer for electrodes process of perovskite solar cell production to ensure the from the sunlight. Their prototype cell possesses a ‘p-i-n cell is not harmed before the metal oxide coating can be structure’ containing indium tin oxide, NiOx, perovskite, applied [3]. This is a very concerning scenario, because ZnO, and aluminum [8]. The nanoparticles act as a air holds a small amount of water vapor, and it is possible shielding around the perovskite and aluminum, protecting that the perovskite solar cell could be ruined before it the perovskite from water vapor. Research conducted on exits the assembly line if it is exposed to this moisture the prototype cell has returned great results: ninety during the process. Preventing exposure during the percent power conversion efficiency after sixty days manufacturing process is potentially the biggest problem exposed to outside air at room temperature [8]. Typical that would arise when this technology is mass produced. perovskite cells without a metal oxide coating can only Researchers and engineers will have to devise a plan for last five days before complete degradation from moisture manufacturing perovskite solar cells that does not involve [8]. This prototype solar cell, coupled with the Japanese the cells being exposed to air during the process. These titanium oxide cell, shows great promise in overcoming manufacturing issues will surface after it is confirmed that the current limitations of perovskite cells. perovskite solar cell metal oxide coatings have the durability to actively protect the solar cells from moisture LIMITATIONS OF PEROVSKITE CELLS for very long periods of time [10].

Perovskite cells seem like the perfect solution for the Lifespan and Sustainability future of energy. They are an economical, sustainable solution to the ensuing problem of depleting fossil fuels Currently, the lifetime of a perovskite solar cell is within the next one hundred years. Despite these positive very dependent on the durability of the metal oxide attributes, a difficult problem of degradation surrounds protective coating that surrounds it. As soon as this metal perovskite solar cell technology that will prevent them oxide begins to wear and allow water to seep through, the from being mass-produced until a resolution is produced. cell will deteriorate to a state beyond repair, rendering the The material of perovskite cannot have any contact with solar cell useless. Current metal oxide coating tests have water vapor. The resulting dilapidation does not just occur shown that with a proper coating, a perovskite solar cell when water condenses onto the solar cell material. It also can remain functional for a full four days of non-stop occurs when even the slightest amount of moisture electricity generation when exposed to air [2]. This length interacts with the delicate surface of the perovskite [2]. In of time before deterioration makes perovskite solar cells a current laboratory setting, perovskite solar cells must be currently useless in terms of practicality. Four days is a tested inside of a vacuum so that absolutely no water very short length of time for a solar cell to remain vapor comes in contact with the material. That is a operational. This length of time would have to increase to condition that makes perovskite relatively difficult to years before perovskite solar cells are considered useful experiment on, compared to other types of solar cells. and economical is the business world. This length of time However daunting, researchers have been exploring is expected to see a great increase as metal oxide coatings innovative solutions to this potentially crippling problem are further researched and the construction methods of of moisture-induced cell degradation. The most popular perovskite solar cells improve. solution is the application of a metal oxide coating to the 4 ENGR0011/0711 Section Group # These small developments of the perovskite compared to current solar cells, perovskite has already technology may lead the average consumer to wrongly begun to take its place on the solar throne. conclude that perovskite does not have the capacity to be sustainable. Sustainability can be viewed from multiple Success in Solar perspectives, primarily agricultural, ecological, and economic [7]. For example, as stated previously, the Solar cells first came into public awareness in the ecological perspective is defined as “meeting human 1970’s. Since their introduction, solar cells have needs without compromising health of ecosystems” [7]. developed into their own industry. The most familiar solar This can conversely be compared to the economic cell is comprised of silicon and is the most cost-effective definition which is very similar except its priority is to solar cell currently. In 2014, the cost of a silicon solar save money, not the environment while furthering the cells was 72 cents per watt, while researchers believe that effectiveness of a product. Although this issue may be perovskite cells could cost as low as 10 to 20 cents per viewed from multiple perspectives, one component watt [2]. This price could make solar cells viable for any remains the same through all of them: one thing is family, regardless of income status. However, due to conserved while another thing is advanced. Perovskite companies driving the development of solar technology, solar cells definitely hold potential to be sustainable, and the solar industry can only grow if profits grow. should be viewed and judged with an open mind. Once According to Figure 4, silicon cells have shown no perfected, perovskite cells will be able to flawlessly improvement on their twenty-five percent efficiency level operate for decades on end. Their efficiency and cost are in the past twenty years. Costs have been driven down, phenomenal for being still so early in development. This yet these same cells have not converted higher rates of technology, with so much potential, will change the way electricity [9]. Instead, leaving silicon as the current the world thinks about solar power. mainstay of solar, researchers have developed other new Perovskite is very efficacious in terms of the various types of solar cells, such as perovskite-based cells. definitions of sustainability. For example, perovskite solar cells are economically sustainable because they are less FIGURE 4 [9] costly and more efficient than the silicon solar cells that they will be competing with in the future on the marketplace. Perovskite will be a very enticing investment option for the business world due to its economic sustainability. In terms of ecological sustainability, perovskite solar cells are phenomenal due to their ability to convert solar radiation into useable power. In addition, perovskite generates a neutral effect on the environment compared to most other major forms of power generation, such as hydroelectric, which may alter rivers and lakes, and fossil fuels, which contribute heavily to the global warming effect. With the help of perovskite solar cells, power generation as a whole can be brought to a higher standard of ecological sustainability due to the eco-friendly nature of perovskite solar cell Graph displaying the levels of efficiencies by year technology. Perovskite solar cell technology offers a (data collected by the NREL) powerful and sustainable source of energy that surmounts the limits of current solar cells. Perovskite solar cells first emerged in 2009 in a laboratory at Toin University in Yokohama, Japan, where APPROACHING THE APEX the researchers created perovskite nanometer crystals by developing the compound out of a chemical solution [2]. With proper research and development, perovskite Adding solar cell metal contacts on the perovskite crystals solar cells could approach the apex of solar cell resulted in a transfer of electrons, resulting in the first technology relatively soon. Scientists from universities all perovskite cell. This cell would be the first step in over the globe, ranging from California to Japan, are becoming a promising alternative to silicon cells. They collaborating on improving this technology. The reached twenty percent efficiency in three years, while it prominent solution being developed is the metal oxide took silicon almost a decade to achieve. Despite this, coating we have discussed throughout this paper. Once perovskite cells come with a condition: these cells are the issue of degradation has been overcome, real-world non-stable [2]. As we discussed at length throughout this tests can be carried out in the open environment. In paper, research has shown glimpses of a solution that addition, research can be further conducted to improve the would not lower the superb efficiency while protecting power-per-weight and levels of efficiency. However, the cell from the elements [9]. Since these debacles must be solved before manufacturing, perovskite cells do not

5 ENGR0011/0711 Section Group # have a large presence in the marketplace, but prototypes Solar energy is a clean, efficient, and economical are still available to examine these remarkable cells. source of energy that has the potential to reshape the way that we approach electricity generation, especially in What’s Available Right Now? urban environments. As shown in Figure 5, perovskite cells possess a record power-per-weight of twenty-three Despite their high power-per-weight and levels of watts per gram. Compared with earlier models of solar efficiency, perovskite solar cells are currently not cells, this level of energy efficiency per weight is available to the majority of the public. However, working unprecedented and will allow perovskite cells to take prototypes have been produced in research laboratories. solar power and the energy industry to brighter future. In Changzhou University in Changzhou, China, Along with a record power-per-weight, perovskite has researchers have developed functioning perovskite cells. reached a confirmed efficiency level of 17.9% in 2014 These cells have been used in different settings, such as [1]. This level is significant due to the exponential rise different levels of humidity, to examine the efficiency in compared to the main-stay silicon solar cell. Perovskite these controlled environments [6]. In addition, as cells could reach the apex of the solar industry once they discussed earlier, the graduate students and professors at have proven able to function in the outside environment. the Japan Institute for Chemical Research and Kyoto If properly integrated into skyscrapers in the form of University fabricated perovskite solar cell prototypes with windows, perovskite could drastically lower the amount a titanium oxide coating. This promising prototype has of power used in urban centers [1]. This would enable shown only a slight decrease in efficiency and the ability perovskite cells to aid cities in sustainable self-production to be used outside of a laboratory environment [5]. of their electricity, which has never been achieved in the Furthermore, other prototypes created with various metal course of human history. Coupled with this fact, oxides have been researched, but will only be improved perovskite cells would allow buildings to be carbon- on once the problem of moisture degradation has a neutral, whereas the buildings would otherwise add onto definite solution. the daily carbon emissions humans cause and contribute A European collaboration between Austrian to the global warming effect. In addition, perovskite cells universities recently manufactured flexible perovskite could be used to power the ensuing drone revolution. As solar cells using an acrylic elastomer. This will be drones are better implemented into society, a viable discussed in the later section on the future possibilities of power source to keep them afloat for longer will be perovskite solar cells, but the ability to be used in any required. As a possible solution, perovskite cells also setting certainly grants perovskite technology countless have a minuscule carbon footprint over their lifetime, but possibilities [1]. These prototypes may not be available to before fulfilling its potential and being used throughout the vast majority of the world, but the potential has society, any impact, positive or negative, of perovskite on companies ready for mass production once perovskite humanity must be considered [2]. cells have been deemed serviceable in the outside environment. Figure 5 [1]

PEROVSKITE’S POTENTIAL

Perovskite solar cell technology is something that has enormous potential to forever change the energy market worldwide. Solar cells made of perovskite have made the same advancements in two years compared to the twenty years it took contemporary silicon cells [6]. From transparent cells to vastly increased efficiencies, perovskite offers a versatile and renewable alternative to current forms of fossil fuel generated energy and its solar brethren. An example of this is the idea of replacing the windows of a skyscraper with fully transparent perovskite solar cells. Not only would it retain the grandeur of the skyscraper, but would also make the skyscraper completely self-sufficient in terms of power generation. A graph of solar cells and their power-per-weight Being transparent, these cells would absorb the electrons from the sunlight, but would not prevent the light from illuminating the rooms inside. By replacing the windows IMPACT ON THE FUTURE AND with clear perovskite cells, a skyscraper could generate SOCIETY electricity for itself and surrounding buildings [1]. These are the types of innovations with perovskite that will help Due to their vast potential, perovskite solar cells are revolutionize the energy industry as we know it, and help poised to take a major part of modern society and the future generations foster renewable sources of energy. future. Compared to current silicon solar cells, 6 ENGR0011/0711 Section Group # perovskites hold a major advantage. Perovskite cells possess a record power-per-weight and efficiency levels on par with silicon [4]. In approximately three years, perovskite has almost matched silicon in its efficiency and surpassed it in power-per-weight. Furthermore, perovskite could become the cheapest solar cell available because it can be made at lower temperatures, requiring less energy and therefore less money. These same cells can be converted to flexible solar cells, allowing them to be placed and utilized in any location or surface [2]. However, before reaching the forefront of the solar industry, perovskite solar technology must prove its application and cost to society. With their dramatic rise amongst their solar brethren, perovskite solar cells do have some opposition other than the issue of moisture degradation. The primary perovskite used is a lead-based compound, which may pose a toxic threat to the global environment. However, preliminary Three-dimensional rendering of a perovskite cell research has shown that the lead in perovskite may be undergoing approximately 40% compressive strain able to be replaced by tin, countering any lead-based issues [4]. In addition, current silicon cells possess similar Perovskite solar cells have many applications in the amounts of lead or cadmium, another toxic element, future due to their blend of critical properties. Once leading to phase-outs by governments, where perovskite commercialized, these cells have the ability to end the presents a positive alternative [3]. Despite these possible global energy crisis, surpassing silicon and other solar challenges, perovskite cells display a prime opportunity to cells [3]. Furthermore, perovskite solar cells have the improve current technology and society as a whole. flexibility to be used to power instruments such as Along with their high power-per-weight and weather balloons, satellites, and unmanned aerial vehicles efficiency, perovskite solar cells are ultra-lightweight and [1]. The high power-per-weight ratio coupled with their flexible solar cells, an unheard of combination until now lightweight properties enable perovskite cells to be used [11]. The perovskite solar cells are only two micrometers in future robotics, such as exoskeletons. Currently, these thick with a one micrometer layer of metal oxide and a cells have been successfully used to power micro-aerial polyurethane commercial coating. Merged with an acrylic robotics, which demonstrates a future in travel, elastomer, perovskite cells become a flexible solar cell, emergency and rescue, and security applications [1]. able to be used on any emerging technologies, including These exciting prospects and properties of perovskite flexible OLED screens and autonomous drones. The solar cells lead us to have a great outlook on the future of ability to be placed on any surface will allow perovskite solar technology. solar cell technology to be used in any environment. As shown in Figure 6, perovskite cells can undergo a THE OUTLOOK considerable amount of strain, which is significant to be utilized in real-world situations. Tests undertaken on Perovskite solar cell technology is a very promising flexible perovskite cells show only a five percent energy form of energy that should be gaining traction within the loss over a thousand cycles [1]. The ability to conform next ten years. Research has provided tremendous itself to any surface and sustain its high performance over evidence of the raw potential that these new solar cells repeated use will allow perovskite cells to have countless have, especially when compared to their silicon incorporations in technology and society. counterparts. From skyscrapers to solar farms, this new form of energy is just as versatile as it is powerful [1]. In FIGURE 6 [1] their short existence, perovskite solar cells have almost topped the efficiencies achieved by traditional silicon solar cells, and perovskite is not stopping there [11]. Extensive research is being done around the world in laboratories dedicated making this technology more efficient and applicable. 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(2015). “Perovskite http://www.library.pitt.edu/other/files/il/fresheng/index.ht Solar Cells: Potentials, Challenges, and Opportunities.” ml International Journal of Photoenergy. (online article). (2015). “New Technique Stabilizes Perovskite Solar http://www.hindawi.com/journals/ijp/2015/592308/ Cells.” Advanced Materials & Processes. (online article). [4] M. A. Green, A. Ho-Baillie, H. J. Snaith. (2014). “The http://search.ebscohost.com/login.aspx? Emergence of Perovskite Solar Cells.” Nature Photonics. direct=true&db=aph&AN=111081644&site=ehost-live. (online article). http://rdcu.be/f4Nt. p. 14. [5] K. Yamamoto, Y. Zhou, T. Kuwabara, et al. (2014). (2016). “Sustainability Mission.” Alcoa Inc. (online “Low Temperature TiOx Compact Layer by Chemcial article). Bath Deposition Method for Vapor Desposited Perovskite http://www.alcoa.com/sustainability/en/home.asp. Solar cells.” Photovoltaic Specialist Conference. (online article). http://ieeexplore.ieee.org/stamp/stamp.jsp? tp=&arnumber=6925218&tag=1. p. 1573-1576. ACKNOWLEDGEMENTS [6] M. Lv, X. Dong, X. Fang, B. Lin, S. Zhang, et al. (2015). “Improved photovoltaic performance in We would like to acknowledge our family and friends perovskite solar cells based on CH3NH3PbI3films who aided us. We would also like to thank our writing fabricated under controlled relative humidity.” RSC instructor Mrs. Nancy Koerbel, our co-chair Alyssa Advances. (online article). Srock, our chair Mr. Richard Velan, our conference https://www.engineeringvillage.com/share/document.url? director Dr. Dan Budny, and our sources of inspiration, Gatsby and Lexie.