File Name: perovskites structure properties and uses .zip
Halide perovskites have emerged as a class of most promising and cost-effective semiconductor materials for next generation photoluminescent, electroluminescent and photovoltaic devices. These perovskites have high optical absorption coefficients and exhibit narrow-band bright photoluminescence, in addition to their halide-dependent tuneable bandgaps, low exciton binding energies, and long-range carrier diffusion.
The rapid improvement of perovskite solar cells has made them the rising star of the photovoltaics world and of huge interest to the academic community. Since their operational methods are still relatively new, there is great opportunity for further research into the basic physics and chemistry around perovskites. The terms "perovskite" and "perovskite structure" are often used interchangeably. Technically, a perovskite is a type of mineral that was first found in the Ural Mountains and named after Lev Perovski who was the founder of the Russian Geographical Society.
The high demand for energy consumption in everyday life, and fears of climate change are driving the scientific community to explore prospective materials for efficient energy conversion and storage.
Perovskites, a prominent category of materials, including metal halides and perovskite oxides have a significant role as energy materials, and can effectively replace conventional materials. The simultaneous need for new energy materials together with the increased interest for making new devices, and exploring new physics, thrust the research to control the structuring of the perovskite materials at the nanoscale.
Nanostructuring of the perovskites offers unique features such as a large surface area, extensive porous structures, controlled transport and charge-carrier mobility, strong absorption and photoluminescence, and confinement effects. These features together with the unique tunability in their composition, shape, and functionalities make perovskite nanocrystals efficient for energy-related applications such as photovoltaics, catalysts, thermoelectrics, batteries, supercapacitor and hydrogen storage systems.
The synthesis procedures of perovskite nanostructures in different morphologies is summarized and the energy-related properties and applications are extensively discussed in this paper. The high demand for energy consumption in everyday life activities along with fears of the climate changes highlight the importance to develop efficient energy conversion and storage devices.
Thus, sufficient energy conversion and storage together with low-cost energy materials are the most important requirements. In order to design such devices, it is crucial to study and understand the underlying principles and mechanisms of renewable energy conversion and storage.
Each of these technologies has its own characteristics, requirements, and efficiency limits or constraints. Different mechanisms take place in each technology and this is the main reason for dealing them independently. The design and engineering of novel materials with a suitable range of properties for the effective utilization for such applications is a basic requirement. The design of new energy-related materials is at the forefront of different sciences such as the material science, chemistry, physics, and engineering.
It is important to reveal the relationship between the material structure and the device performance if we wish to propose new energy-related materials [ 1 ], [ 2 ], [ 3 ]. In the quest to find prospective energy materials for high performance energy devices, the perovskite compounds hold a prominent role due to their unique tunable properties [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ]. Perovskites are a family of materials with the formula ABX 3 and have a similar structure to the prototype CaTiO 3 mineral.
This family comprises oxides and halide perovskite material. According to the nature of the cation, the metal halides can be divided in two groups, the all-inorganic and the hybrid organic-inorganic metal halides. In the first category the cation A is a monovalent alkali metal like Cs, K while in the second it is a small organic cation such as CH 3 NH 3 [ 10 ], [ 11 ].
The exploitation of new synthesis methods for the fine control of the structural characteristics and improved stability is important in the design of perovskite energy-related materials. Furthermore, the progress on the synthesis strategies for nanoparticulate systems of high quality in terms of homogeneity and crystallinity, has led the research community to search whether these materials could replace conventional energy materials.
Different morphologies and chemical structures have been introduced for both metal halide and perovskite oxide nanocrystals for such purposes [ 1 ], [ 12 ], [ 13 ]. Metal halide nanocrystals can be effectively used in energy conversion, due to their strong optical absorption, low non-radiative recombination rates, tunable band gaps, relatively high charge-carrier mobility, and long diffusion lengths coupled with solution processability [ 14 ]. These nanocrystals have been utilized as the absorbing material in perovskite solar cells [ 15 ], [ 16 ] or placed at the interface between the absorbing and the hole transport layer HTL in order to improve carrier transport and stability [ 17 ], [ 18 ].
They are also used as down-converters in silicon solar cells due to their excellent quantum-cutting properties giving efficiencies of In contrast, perovskite oxide nanocrystals have been utilized as electron transport layers ETLs in perovskite solar cells, as these materials are characterized by high electron mobility, wide band-gap, and a well-aligned conduction band with the absorbing layer [ 20 ].
Furthermore, perovskite nanocrystals have been tested for catalytic carbon dioxide CO 2 reduction in solar fuel cells. By mimicking the natural photosynthesis in green plants, artificial conversion of CO 2 into chemical fuels offers a promising approach to simultaneously mitigate the levels of greenhouse gas and produce renewable energy [ 21 ].
Single-phase metal halide nanocrystals have shown promising results in CO 2 reduction [ 22 ], [ 23 ], but enhanced performance when these are coupled with graphene oxide GO or palladium nanosheets [ 24 ], [ 25 ].
Besides, the perovskite materials are promising materials for thermoelectrics for the conversion of thermal energy to electricity [ 26 ], [ 27 ]. Compared to the traditional materials used for thermoelectric applications metal chalcogenide materials like Bi 2 Te 3 and PbTe , perovskite materials are less expensive and can be processed by low energy cost methods and can be used for flexible thermoelectric devices [ 27 ]. The fairly ionic, polar character with a large dielectric constant and the remarkable conduction band anisotropy of the metal halides convey robust thermopower and moderate room temperature electrical conductivity [ 28 ].
Perovskite nanocrystals have been utilized in energy storage in batteries or supercapacitors due to their excellent catalytic activity, electrical conductivity, and durability.
Ion migration through perovskite lattices allows the use of such materials as electrodes for batteries. Electrochemical measurements of the nanoparticulate perovskite systems displayed superior catalytic activity for oxygen reduction, as well as a higher discharge plateau and specific capacity compared to the bulk materials of the same crystal structure [ 29 ]. Metal halide nanocrystal films have been formed for application as anodes, for stable Li-based batteries [ 30 ], [ 31 ], [ 32 ].
Furthermore, in the case of the perovskite oxides, the size and the morphology of the nanocrystals are two factors that affect their electrochemical performance. In addition, in the case of supercapacitor storage, it was found that structuring perovskite oxides and forming nanocrystals lead to remarkably enhanced, specific capacitance, rate capability, and cycle stability compared to the corresponding bulk materials [ 47 ], [ 48 ], [ 49 ].
Finally, perovskite nanocrystals offer improved electrochemical performance, low cost production in hydrogen storage and energy sustainability for transportation, electricity generation, and heating. Perovskite oxide nanocrystals show a higher discharge capacity compared to the bulk counterpart of the same stoichiometry [ 50 ] and in some cases is comparable to that of common materials that have been used for hydrogen storage to date [ 51 ].
Several review articles have been published on the application of nanocrystals in energy conversion and storage in the last couple of years [ 52 ], [ 53 ], [ 54 ], [ 55 ], [ 56 ], [ 57 ]. This review article seeks to summarize the colloidal methods of the perovskite nanocrystals both for metal halides and perovskite oxides but mainly focuses only on the applications of the nanoparticulate structures Figure 1. This review is structured in three main sections: Section 2 deals with the synthesis strategies, morphology, and size control of the single-phase perovskite nanocrystals, Section 3 looks at perovskite nanocrystals for energy conversion, and Section 4 deals with perovskite nanocrystals for energy storage.
In all these sections, we have summarized the literature for both metal halide and perovskite oxide nanocrystals and discuss the effect of structure, morphology, and size in the performance of these devices.
This review article concludes with some open issues that require attention to succeed in designing efficient and low-cost devices. Applications of perovskite metal halides and perovskite oxides nanocrystals for energy conversion and storage. Different methods have been introduced for the successful synthesis of perovskite nanocrystals. Metal halides have been synthesized by template-assisted methods and colloidal-based reactions, while perovskite oxides are created by solid-state or molten-salt reactions and colloidal processes.
Due to the limited use in energy application of the metal halide nanocrystals synthesized by template-assisted methods we will focus only on the colloidal methods. In the case of the oxides, despite the fact that the solid state and molten-salt syntheses are more convenient compared to the colloidal ones, the latter have the advantage of achieving a better control of the characteristics of nanocrystals. Colloidal methods were used for the synthesis of both metal-halide and perovskite oxide nanocrystals of different morphology, isotropic or anisotropic one Figure 2.
In most cases, the metal halide nanocrystals were covered with organic molecules, usually acids and amines, while in the case of perovskite oxides, they are free of ligands Table 1. Summary of the solution-processed synthesis procedures of various perovskite nanocrystal morphologies. Metal halides: a Nanospheres synthesized by a hot method. Reprinted with permission from [ 58 ] Copyright , American Chemical Society. Reproduced by permission of the Royal Society of Chemistry [ 59 ].
Reprinted with permission from [ 60 ]. Copyright , American Chemical Society. Reproduced by permission of the Royal Society of Chemistry [ 61 ]. Reproduced with permission from [ 62 ]. Copyright , Wiley-VCH. Perovskite oxides: a Irregular-shaped nanocrystals synthesized by sol-gel method. Reproduced with permission from [ 63 ]. Copyright , Elsevier. Reprinted with permission from [ 64 ].
Reproduced with permission from [ 65 ]. Reproduced from [ 66 ] with permission from the Royal Society of Chemistry. The first category comprises processes which start from molecules and ions and proceed with chemical reactions.
In this type of reaction, the presence of capping ligands is important to control the size, morphology, and dispersity of the final nanocrystals. The second category includes the fragmentation of larger particles by an external stimulus such as irradiation or sonication in the presence of ligands or not.
The first one is a low-temperature process while the other two take place at high temperatures. All of them share common characteristics but have important differences [ 1 ]. For example, the re-precipitation methods are quick procedures, cost-effective, reproducible, they do not need complex apparatus, such as Schlenk line and inert gas flow, and are suitable for large-scale production.
The hot-injection processes have a unique capability to finely control the shape and morphology of the nanocrystals, and also to produce complex structures with high homogeneity. This procedure is a time consuming procedure; it uses a Schlenk line coupled with a protective atmosphere and produces a small amount of the final product.
Finally, the solvothermal process gives very good control of the nanocrystals by using a simple set-up, but the time duration of the reactions is a significant disadvantage of this procedure. This solution-based process has been introduced to synthesize nanocrystals of different morphologies and chemical phases. The metal precursors are dissolved in a solvent usually in the presence of capping molecules. Then, this solution is added in a miscible co-solvent in which the solubility of the ions is low.
Spontaneous crystallization and precipitation take place. This procedure has been proposed for both hybrid organic-inorganic or all inorganic metal halide nanocrystals and morphologies such as nanospheres [ 68 ], [ 69 ], [ 70 ], [ 71 ], [ 72 ], [ 73 ], nanocubes [ 71 ], [ 72 ], [ 74 ], [ 75 ], [ 76 ], nanohexagons [ 32 ], [ 76 ], nanorods [ 70 ], [ 71 ], [ 72 ], [ 77 ], nanowires [ 61 ], [ 70 ], [ 72 ], [ 78 ], nanoplatelets [ 70 ], [ 71 ], [ 72 ], [ 79 ], [ 80 ], [ ], and nanosheets [ 70 ], [ 81 ].
In addition, such methods were reported last years for the synthesis of lead-free nanocrystals with quantum dot morphology [ ], [ ], [ ]. The precursors in this reaction were CH 3 NH 3 Br and PbBr 2 while the capping molecules were the oleic acid together with long chain alkyl ammonium bromide.
The dispersive solvent was octadecene while the co-solvent was acetone. Later, in , in order to simplify this procedure, commercially available precursors and capping ligands n-octylamine and oleic acid were used [ 69 ]. This modified procedure resulted in similar morphologies but smaller in size 3 nm.
N-dimethylformamide DMF was used as dissolving solvent and toluene as co-solvent. By combining organic molecules of a long and a short chain, nanoplatelet morphologies were formed [ 79 ]. Their lateral dimensions can be tuned by regulating the surfactant ratio while by adjusting the oleic acid amount one can obtain very thin platelets down to one layer. By changing the ratio between octylamonium bromide and oleic acid, the particles can be changed from spheres to anisotropic nanorods [ 77 ].
The amines found mainly affect the size of the nanocrystals by controlling the kinetics of crystallization while the acids suppress the aggregation effects and contribute to the stability of the colloids [ 69 ].
Furthermore, the way of adding the precursor solution can affect the final size of the nanocrystals [ 70 ], [ ].
A longer duration of the addition of the precursor results in larger particles through an Ostwald ripening mechanism [ 72 ] or anisotropic morphologies [ 70 ]. The type of solvent and co-solvent in which the precursors are dissolved can also affect the morphology of the final nanocrystals.
While when the cosolvent was the ethyl acetate, the obtained morphology is varied from dots to nanoplates to nanobars by increasing the reaction time while by using toluene the nanocrystals transform from nanocubes to nanorods to nanowires [ 72 ].
Metal halide nanocrystals have been synthesized via ultrasonication techniques. The solution of the reactants together with the organic ligands are positioned in a high density probe-type ultrasonicator in order to fabricate cubic or platelet-like crystals [ 59 ], [ ].
This synthesis procedure is utilized for both lead-containing or lead-free metal halide nanocrystals Table 1. This process includes the injection of a precursor solution in a hot liquid of the surfactants.
The uses for these materials are based upon their intrinsic dielectric, ferroelectric, piezoelectric, and pyroelectric properties of relevance in corresponding electronics applications such as electromechanical devices. The general chemical formula for perovskite compounds is. May 04, hybrid perovskites are a mix of organic and inorganic ions with the same crystal structure as calcium titanium oxide catio3. These films can be a couple of nanometres thick or as small as a single unit cell. Synthesis, structure, and properties of new perovskite. Ruddlesonpopper phases are identifiable from other layered perovskites by the cationic bilayer separating individual. Perovskites can be deposited as epitaxial thin films on top of other perovskites, using techniques such as pulsed laser deposition and molecularbeam epitaxy.
The high demand for energy consumption in everyday life, and fears of climate change are driving the scientific community to explore prospective materials for efficient energy conversion and storage. Perovskites, a prominent category of materials, including metal halides and perovskite oxides have a significant role as energy materials, and can effectively replace conventional materials. The simultaneous need for new energy materials together with the increased interest for making new devices, and exploring new physics, thrust the research to control the structuring of the perovskite materials at the nanoscale. Nanostructuring of the perovskites offers unique features such as a large surface area, extensive porous structures, controlled transport and charge-carrier mobility, strong absorption and photoluminescence, and confinement effects. These features together with the unique tunability in their composition, shape, and functionalities make perovskite nanocrystals efficient for energy-related applications such as photovoltaics, catalysts, thermoelectrics, batteries, supercapacitor and hydrogen storage systems.
A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite CH 3 NH 3 PbX 3 materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and focus on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.
This review presents a full coverage of the structure, progress of perovskites and their related applications. Stress is focused particularly to.
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