Hybrid Halide Perovskites Research Articles

Unveiling the Interaction Mechanisms of Electron and X-ray Radiation with Halide Perovskite Semiconductors using Scanning Nanoprobe Diffraction.

The interaction of high-energy electrons and X-ray photons with beam-sensitive semiconductors such as halide perovskites is essential for the characterization and understanding of these optoelectronic materials. Using nanoprobe diffraction techniques, which can investigate physical properties on the nanoscale, studies of the interaction of electron and X-ray radiation with state-of-the-art (FA0.79 MA0.16 Cs0.05 )Pb(I0.83 Br0.17 )3 hybrid halide perovskite films (FA, formamidinium; MA, methylammonium) are performed, tracking the changes in the local crystal structure as a function of fluence using scanning electron diffraction and synchrotron nano X-ray diffraction techniques. Perovskite grains are identified, from which additional reflections, corresponding to PbBr2 , appear as a crystalline degradation phase after fluences of 200 e- Å- 2 . These changes are concomitant with the formation of small PbI2 crystallites at the adjacent high-angle grain boundaries, with the formation of pinholes, and with a phase transition from tetragonal to cubic. A similar degradation pathway is caused by photon irradiation in nano-X-ray diffraction, suggesting common underlying mechanisms. This approach explores the radiation limits of these materials and provides a description of the degradation pathways on the nanoscale. Addressing high-angle grain boundaries will be critical for the further improvement of halide polycrystalline film stability, especially for applications vulnerable to high-energy radiation such as space photovoltaics.

A Hybrid Halide Perovskite Birefringent Crystal.

Birefringent crystals that can modulate the polarization of light play a significant role in modern optical devices including polarizing microscopes, optical isolators, and achromatic quarter-wave plates. To date, commercial birefringent crystals are exclusively limited to purely inorganic compounds. Here we report a new organic-inorganic hybrid halide, MLAPbBr4 (MLA=melamine), which features a (110)-oriented layered perovskite structure. Although the 6s2 lone-pair electrons of Pb2+ cations are stereochemically inert, MLAPbBr4 exhibits a birefringence of 0.322@550 nm, which exceeds those of all commercial birefringent crystals. The first-principles calculations reveal that this birefringence should be ascribed to the highly dislocated π-conjugation of MLA cations and high distortion of PbBr6 octahedra. This work highlights the persistently neglected great potential of hybrid halide perovskites as birefringent crystals.

A Hybrid Halide Perovskite Birefringent Crystal

AbstractBirefringent crystals that can modulate the polarization of light play a significant role in modern optical devices including polarizing microscopes, optical isolators, and achromatic quarter‐wave plates. To date, commercial birefringent crystals are exclusively limited to purely inorganic compounds. Here we report a new organic–inorganic hybrid halide, MLAPbBr4 (MLA=melamine), which features a (110)‐oriented layered perovskite structure. Although the 6s2 lone‐pair electrons of Pb2+ cations are stereochemically inert, MLAPbBr4 exhibits a birefringence of 0.322@550 nm, which exceeds those of all commercial birefringent crystals. The first‐principles calculations reveal that this birefringence should be ascribed to the highly dislocated π‐conjugation of MLA cations and high distortion of PbBr6 octahedra. This work highlights the persistently neglected great potential of hybrid halide perovskites as birefringent crystals.

Progress in Organic-Inorganic Hybrid Perovskite Solar Cells: Architecture, Efficiency and Stability

In recent years, it has been established that solar cells based on organic-inorganic hybrid perovskite materials have substantial potential for the development of highly efficient photovoltaic devices and offers robust opportunities for research to the scientific community and industry. Power conversion efficiency (PCE) of perovskite solar cells (PSCs) have already surpassed 24.8 % within a decade, which is now third highest efficiency among single-junction photovoltaic materials. This report briefly introduces hybrid-halide perovskite materials, their structural properties, various possible device architectures and a comparative study of photo-voltaic performance. For commercialization, high stability of devices is must and here we have thoroughly discussed possible degradation mechanisms of PSCs, that is, moisture; oxygen; heat; structural stability; UV-light effect; defect-states, ion-migration and various approaches to passivity based upon recent reports. A proper encapsulation with optimized chemical composition (enhanced interaction between organic/inorganic cation and BX6 octahedron) PSCs could possess superior stability for long-run while maintaining optoelectronic properties.

Chemistry, Structure, and Function of Lone Pairs in Extended Solids.

ConspectusThe lone pair has been a known feature of the electronic structure of molecules for over 100 years. Beginning with the pioneering work of Lewis and others that was later developed into useful guidelines for predicting molecular structure, lone pairs and their steric consequences are now taught at the very earliest stages of a chemistry education. In the crystalline solid state, lone pairs have perhaps had a less visible yet equally consequential role, with a significant impact on a range of properties and functionalities. Important properties associated with s2 electron-derived lone pairs include their role in creating conditions favorable for ion transport, in the formation and correlation of local dipoles and the resulting polar behavior leading to ferroics and multiferroics, in increasing the refractive index of glass, in reducing the thermal conductivity of thermoelectric materials, and in breaking local symmetry permitting second-harmonic light generation.. In recent years, the role of the lone pair in developing the electronic structure of some topological quantum materials has also been recognized. While structural distortions due to lone pairs have traditionally been characterized through their crystallography, recent advances in scattering and spectroscopy have revealed the presence of local lone pair-driven distortions that do not correlate over long length scales. The role of these crystallographically "hidden" lone pairs, their detection, and their impact on properties have become a growing body of work in the literature. Hidden lone pairs are an effective argument for considering a role for lone pairs that goes beyond their being objects that occupy space in the coordination polyhedra of cations. This Account introduces the chemistry of lone pairs in extended crystalline solids, including a discussion of when they are stereochemically active, how they manifest in the structure, and how their chemistry can be tuned by the chemical environment around them. Eventually, all of these factors work in unison to help develop and tune properties of interest. Certain specific examples of structure-property relationships in materials that are driven by lone pair behavior are described here, including the potential impact of lone pairs on the optical and electronic properties of hybrid halide perovskite compounds that are relevant to their photovoltaic applications. We highlight the role of lone pairs in the dielectric behavior of geometrically frustrated pyrochlores, the temperature-dependent optoelectronic behavior of halide perovskites, the polar phase transitions in lead-free ferroelectric perovskites, and the compositional insulator-to-metal transition in ruthenium pyrochlores. The theme underpinning this Account is that the lone pair can be considered to be a powerful design element for a broad range of material function.

The lead-free perovskite solar cells with the green synthesized BiI3 and AgI nanoparticles using Vitex agnus-castus plant extract for HTM-free and carbon-based solar cells

A green BiI3 and AgI nanoparticles were synthesized using Vitex agnus-castus and then these nanoparticles were applied to obtain a high-quality methylammonium bismuth iodide ((CH3NH3I)3Bi2I9 = MBI) and AgBi2I7 as perovskite film. BiI3, MBI, and AgBi2I7 nanoperovskites have been proposed as viable candidates for concurrently resolving the instability and lead toxicity difficulties of unprecedented organic-inorganic hybrid halide perovskites. When the contact area between BiI3 and MBI and also AgI and BiI3 were increased due to the nanostructure of BiI3 and AgI, the reaction rate between BiI3 and methylammonium iodide (MAI) and also AgI and BiI3 was enhanced. Therefore, uniform and high crystalline perovskites layers without BiI3 residue was prepared. In this study, the vital role of the nanostructure perovskite layer in the stability and performance of the device is discussed.This resulted in a significant increase in power conversion efficiency (PCE), which reached 1.42%, as well as stability up to 7 days of AgBi2I7 solar cells against humidity, heat and light. Furthermore, without encapsulation, these devices exhibit superior tolerance under air conditions and high temperatures, providing new opportunities to promote the future development of lead-free AgBi2I7 nanoperovskites in the photoelectric field.

Chalcogenide BaZrS3 perovskite solar cells: A numerical simulation and analysis using SCAPS-1D

Chalcogenide perovskites (CPs), especially Barium Zirconium Sulfide (BaZrS3), have attracted tremendous attention as a potential alternative to hybrid halide perovskites for optoelectronics due to their exceptional visible light absorption and extraordinary chemical stability. Therefore, we numerically investigated a highly efficient n-i-p CPs model solar cells using the Solar cell simulator capacitance software (SCAPS-1D), consisting of a conventional (i.e., BaZrS3 – 1.9 eV), as well as Ti and S, incorporated absorbers (i.e., Ba(Zr0.95Ti0.05)S3 – 1.63 eV and BaZr(S0.6Se0.4)3–1.76 eV). The systematic studies explored the varying CPs absorber layer properties, the effects of thickness, total and interface (i.e., ETL/CPs and CPs/HTL) defect densities and optimized parameters for ideal device performance. The optimized solar cell parameters yielded a power conversion efficiency (PCE) of 12.42% for BaZrS3, 18.85% for Ba(Zr0.95Ti0.05)S3 and 15.47% for BaZr(S0.6Se0.4)3 devices, respectively. The study also explored some effects limiting device performance (i.e., interface and surface states) and resultant current leakages or charge recombination, leading to parasitic resistances (RSeries and RShunt). The quantification of the influence of parasitic resistances and working temperatures provided some insight into the device performance, which appear to be reduced with increasing operating temperature and series resistances. These results suggest that chalcogenide BaZrS3 - based perovskites can play a major role as absorber materials towards highly efficient and cheap perovskite solar cells with low environmental impact.

Two-dimensional hybrid halide perovskites composed of mixed corner- and edge-shared octahedron as broadband yellow-light emissions

Herein, we reported two new 2D perovskites of [DAPMA]2Pb3X12·2H2O (X = Cl (1), Br (2), DAPMA = N,N-Bis(3-aminopropyl)methylamine) containing special 2D [Pb3X12]6− layers formed by mixed corner- and edge-shared [PbX6] octahedrons. Both compounds 1 and 2 exhibit broadband yellow light emissions with promising photoluminescence quantum yields of 4.84% and 3.02%, respectively. According to detailed spectroscopy characterizations, the broadband light emissions should originate from self-trapped excitons (STEs). In addition, these 2D perovskites can be fabricated as white LEDs with highest color rendering index of 96.3%. This work provides a new type of structural model to probe into the relationship between luminescence behavior and structure.

Electrode Engineering in Halide Perovskite Electronics: Plenty of Room at the Interfaces.

Contact engineering is a prerequisite for achieving desirable functionality and performance of semiconductor electronics, which is particularly critical for organic-inorganic hybrid halide perovskites due to their ionic nature and highly reactive interfaces. Although the interfaces between perovskites and charge-transporting layers have attracted lots of attention due to the photovoltaic and light-emitting diode applications, achieving reliable perovskite/electrode contacts for electronic devices, such as transistors and memories, remains as a bottleneck. Herein, a critical review on the elusive nature of perovskite/electrode interfaces with a focus on the interfacial electrochemistry effects is presented. The basic guidelines of electrode selection are given for establishing non-polarized interfaces and optimal energy level alignment for perovskite materials. Furthermore, state-of-the-art strategies on interface-related electrode engineering are reviewed and discussed, which aim at achieving ohmic transport and eliminating hysteresis in perovskite devices. The role and multiple functionalities of self-assembled monolayers that offer a unique approach toward improving perovskite/electrode contacts are also discussed. The insights on electrode engineering pave the way to advancing stable and reliable perovskite devices in diverse electronic applications.

Revisiting the Cu-Zn Disorder in Kesterite Type Cu2ZnSnSe4 Employing a Novel Approach to Hybrid Functional Calculations

In recent years, the search for more efficient and environmentally friendly materials to be employed in the next generation of thin film solar cell devices has seen a shift towards hybrid halide perovskites and chalcogenide materials crystallising in the kesterite crystal structure. Prime examples for the latter are Cu2ZnSnS4, Cu2ZnSnSe4, and their solid solution Cu2ZnSn(SxSe1−x)4, where actual devices already demonstrated power conversion efficiencies of about 13 %. However, in their naturally occurring kesterite crystal structure, the so-called Cu-Zn disorder plays an important role and impacts the structural, electronic, and optical properties. To understand the influence of Cu-Zn disorder, we perform first-principles calculations based on density functional theory combined with special quasirandom structures to accurately model the cation disorder. Since the electronic band gaps and derived optical properties are severely underestimated by (semi)local exchange and correlation functionals, supplementary hybrid functional calculations have been performed. Concerning the latter, we additionally employ a recently devised technique to speed up structural relaxations for hybrid functional calculations. Our calculations show that the Cu-Zn disorder leads to a slight increase in the unit cell volume compared to the conventional kesterite structure showing full cation order, and that the band gap gets reduced by about 0.2 eV, which is in very good agreement with earlier experimental and theoretical findings. Our detailed results on structural, electronic, and optical properties will be discussed with respect to available experimental data, and will provide further insights into the atomistic origin of the disorder-induced band gap lowering in these promising kesterite type materials.

Microstructure of Methylammonium Lead iodide Perovskite Thin Films: A Comprehensive Study of the Strain and Texture

AbstractControlling the microstructure of hybrid halide perovskite thin films is essential for optimizing their performance in optoelectronic devices. It is well established that the strain state of the perovskite layer affects its stability. Likewise, the orientation of the perovskite lattice is a determining parameter as these materials have shown pronounced anisotropies in their physical and mechanical properties. In this work, the authors focus on the understanding of the mechanisms that govern the strain and texture observed in MAPbI3 thin films deposited on various oxide substrates. A thorough study of the evolution of the strain of the perovskite layer upon cooling down to room temperature from the crystallization temperature (100 °C) shows an essentially relaxed behavior of the perovskite layers. This result contradicts the commonly accepted hypothesis according to which MAPbI3 layers synthesized above ambient temperature are strained due to the large mismatch in the thermal expansion coefficients of the perovskite and its substrate. The texture in MAPbI3 layers is investigated by means of synchrotron full‐field diffraction X‐ray microscopy. This technique allows the direct observation of the [hh0] and [00l]‐oriented domains at the origin of the observed textures, demonstrating both their twin and ferroelastic nature. The stability of the different domain orientations is investigated by DFT calculations, illustrating the determining role of the chemical environment at the film‐substrate interface. PbI2‐ terminated surfaces are found to favor the [hh0] orientations while for MAI‐terminated ones, both [hh0] and [00l] domains are equally stabilized. The different results constitute an important step of clarification and understanding from the perspective of controlling the microstructure of perovskite layers.

Effect of dye on luminescent and nonlinear optical properties of bis(4-methoxybenzylammonium) tetra-chlorido cadmate (4MBA2CdCl4) perovskite

We report luminescence and optical limiting (OL) applications of pure and doped layered hybrid halide perovskite (LHHP). Rhodamine B (Rh B), an organic laser dye, was doped in bis(4-methoxybenzylammonium) tetra-chlorido cadmate (4MBA2CdCl4). A simple and cost-effective slow solvent evaporation technique was utilized for crystallization of the perovskites. Formation of both pure and doped 4MBA2CdCl4 were confirmed from the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) studies. 4MBA2CdCl4 crystallized as a layered perovskite where organic layers (4MBA+) are sandwiched between the distorted inorganic CdCl4− octahedral layers. The perovskites are thermally stable up to 276 °C and are flexible up to a load of 50 g. Optical absorption of pure perovskite falls in UV region and is highly transparent for visible light. But, inclusion of Rh B reflected a new absorption peak in the visible region. Also, the luminescence under UV excitation of 4MBA2CdCl4 modified due to doping of dye and it exhibit strong golden yellow luminescence. Nonlinear optical (NLO) properties of pure and doped 4MBA2CdCl4 were also studied by Z-scan technique using 785 nm continuous wave (CW) laser. The perovskites exhibited reverse saturable absorption (RSA) and self-defocusing. Further, both perovskites demonstrate optical limiting properties with a low intensity threshold of 0.8 MW/m2. Rh B incorporated 4MBA2CdCl4 exhibit interesting and enhanced photoluminescence and OL behaviours.

Cryogenic Focused Ion Beam Enables Atomic-Resolution Imaging of Local Structures in Highly Sensitive Bulk Crystals and Devices.

With the development of ultralow-dose (scanning) transmission electron microscopy ((S)TEM) techniques, atomic-resolution imaging of highly sensitive nanomaterials has recently become possible. However, applying these techniques to the study of sensitive bulk materials remains challenging due to the lack of suitable specimen preparation methods. We report that cryogenic focused ion beam (cryo-FIB) can provide a solution to this challenge. We successfully extracted thin specimens from metal–organic framework (MOF) crystals and a hybrid halide perovskite single-crystal film solar cell using cryo-FIB without damaging the inherent structures. The high quality of the specimens enabled the subsequent (S)TEM and electron diffraction studies to reveal complex unknown local structures at an atomic resolution. The obtained structural information allowed us to resolve planar defects in MOF HKUST-1, three-dimensionally reconstruct a concomitant phase in MOF UiO-66, and discover a new CH3NH3PbI3 structure and locate its distribution in a single-crystal film perovskite solar cell. This proof-of-concept study demonstrates that cryo-FIB has a unique ability to handle highly sensitive materials, which can substantially expand the range of applications for electron microscopy.

Ferroelectricity in a semiconducting all-inorganic halide perovskite.

Ferroelectric semiconductors are rare materials with both spontaneous polarizations and visible light absorptions that are promising for designing functional photoferroelectrics, such as optical switches and ferroelectric photovoltaics. The emerging halide perovskites with remarkable semiconducting properties also have the potential of being ferroelectric, yet the evidence of robust ferroelectricity in the typical three-dimensional hybrid halide perovskites has been elusive. Here, we report on the investigation of ferroelectricity in all-inorganic halide perovskites, CsGeX3, with bandgaps of 1.6 to 3.3 eV. Their ferroelectricity originates from the lone pair stereochemical activity in Ge (II) that promotes the ion displacement. This gives rise to their spontaneous polarizations of ~10 to 20 μC/cm2, evidenced by both ab initio calculations and key experiments including atomic-level ionic displacement vector mapping and ferroelectric hysteresis loop measurement. Furthermore, characteristic ferroelectric domain patterns on the well-defined CsGeBr3 nanoplates are imaged with both piezo-response force microscopy and nonlinear optical microscopic method.

First-principles insight into the structural and optoelectronic properties of Sn- and Pb-based hybrid halide perovskites for photovoltaic applications

In this work, we have theoretically investigated structural and optoelectronic properties of Sn and Pb halide perovskites incorporating trimethylammonium (TMA) organic cation by employing density functional theory formalism. Here, our focus is to devise less toxic, efficient and stable perovskite materials for application in photovoltaics. From the calculation of formation energy () and tolerance factor, it is found that both TMAPbX and TMASnX exhibit structural and thermal stability. From the observed band gap values and Bader charge analysis, it can be inferred that halide ions play an important role in tuning the electronic properties of the designed Organic inorganic hybrid halide perovskite (OIHP) materials. Our results also reveal that compounds with I ion possess lower value of fundamental band gap and higher thermal stability. Reorganisation energies indicate that our designed compounds will predominantly act as hole transporting material. The calculated theoretical power conversion efficiency (η) indicates that TMASnI may act as an alternative material for Pb-based perovskite materials. Moreover, TMASnX shows strong absorption in the visible range of electromagnetic spectrum therefore, it is imperative to replace Pb by Sn to fabricate less toxic OIHP material.

Study on the halide effect of MA4PbX6·2H2O hybrid perovskites – From thermochromic properties to practical deployment for smart windows

Thermochromic smart windows empowered by the unique material properties and reversible thermochromism of dihydrated methylammonium lead halide hybrid perovskites (MA4PbX6·2H2O; X: halide) have risen as novel yet promising candidates for thermochromic smart windows, in which the halide plays a crucial role to the functionality and performance. In this study, the effects of halide types and mixing ratios on the thermochromic properties and practical deployment of MA4PbX6·2H2O halide hybrid perovskites are comprehensively studied by extensive fabrication and characterization processes as well as fundamental and applicational investigation tools. The potential perovskite compositions for thermochromic smart window applications are identified with respect to the desired optical properties (i.e. luminous transmittance and solar modulation ability) and transitional properties (i.e. transition temperature, hysteresis width and transition time). Moreover, thermal-regulating performance of the applicable candidate mixed halide hybrid perovskite MA4PbI5Br1·2H2O is demonstrated in a model-house field investigation. This work provides not only an inclusive database of the thermochromic properties of MA4PbX6·2H2O halide hybrid perovskites, but also an application manual about their deployment for thermochromic smart windows, facilitating the development of smart windows and sustainable buildings.

Fabrication of an FAPbBr3/g-C3N4 heterojunction to enhance NO removal efficiency under visible-light irradiation

The FAPbBr 3 /g-C 3 N 4 heterostructures show excellent photocatalytic activity for NO reduction under visible light irradiation. • An FAPbBr 3 /g-C 3 N 4 heterojunction is a new type of photocatalytic composite. • FAPbBr 3 /g-C 3 N 4 composites show excellent NO removal efficiency under irradiation. • The best removal rate is 58%, which is much higher than that of FAPbBr 3 and g-C 3 N 4 . • The photocatalytic mechanism of Type-II heterojunction for NO removal is discussed. Previously, many methods have been used to reduce NOx pollution. Semiconductor photocatalytic oxidation technology has been widely used among those methods because of its environmental friendliness, high efficiency, and simple implementation. Hybrid halide perovskites with exceptional optical properties prove to be promising photocatalysis material; however, their high surface energy, unpaired bonds, and instability are obstacles to large-scale application. In this work, FAPbBr 3 /g-C 3 N 4 heterostructures were successfully synthesized by growing FAPbBr 3 nanocrystals on 2D g-C 3 N 4 nanosheets. Compared with the pristine elements, FAPbBr 3 /g-C 3 N 4 composites show significant NO removal efficiencies under 600 ppb concentration at room temperature. The high performance could be attributed to the formation of a type-II heterojunction and accelerated the separation and transfer of electrons and holes. Furthermore, cycling experiments and XRD results verify that the FAPbBr 3 /g-C 3 N 4 heterojunction owns good stability. Thus, this work not only shows the great potential prospect of halide perovskite for the photocatalysis field, but also demonstrate its promise in solving energy issues and environment science.

Mechanosynthesis strategy towards a high-efficiency CsPbBr3/Cs4PbBr6 perovskite phosphor

All-inorganic perovskites are promising alternatives to organic-inorganic hybrid halide perovskites in the field of optoelectronic materials. Optimizing the luminescent property of CsPbBr3 is very important to promote its application in optoelectronic devices, and thus a facilitative method to prepare a large number of efficient luminous samples is desirable. In this study, we effectively improve the luminous performance of CsPbBr3 powder by a simple mechanosynthesis strategy. The emission intensity of CsPbBr3 powder is improved by ca. 40 times and the PLQY of the powder sample exceeds 40%. It is disclosed that the defects of CsPbBr3 are passivated and the ratio of the non-radiation recombination is reduced. The formed Cs4PbBr6 during grinding has a zero-dimensional perovskite structure that can limit the migration of the carriers between the [PbBr6] octahedrons. Now CsPbBr3 can be used in powder form other than film or quantum dots. A UV-chip LED is fabricated by using the prepared phosphor, and the narrow-band emission property (FWHM is 22 nm) makes it more suitable for application in back-lighting systems.

Film formation mechanisms in mixed-dimensional 2D/3D halide perovskite films revealed by in situ grazing-incidence wide-angle X-ray scattering

<h2>Summary</h2> Mixed-dimensional 2D/3D hybrid halide perovskites retain the stability of 2D perovskites (formula (A′)2(A)_n−1Pb_nI_3n+1) and long diffusion lengths of the 3D materials (AMX₃), thereby affording devices with extended stability as well as state-of-the art efficiencies approaching those of the 3D materials. These films are made by spin-coating precursor solutions with an arbitrarily large average layer thickness <i>n</i> (⟨<i>n</i>⟩ > 7) to give films with both 2D and 3D phases. Although the 2D and 3D perovskite film formation mechanisms have been studied, little is understood about composite 2D/3D film formation. We used <i>in-situ</i> grazing-incidence wide-angle scattering with synchrotron radiation to characterize the films fabricated from precursor solutions with stoichiometries of (BA)₂(MA)_n−1Pb_nI_3n+1 (⟨<i>n</i>⟩ = 3, 4, 5, 7, 12, 50, and ∞ (MAPbI₃)). Four different mechanisms are seen depending on the stoichiometry in the precursor solution. Kinetic analysis shows faster and earlier growth of the solvate with increasing ⟨<i>n</i>⟩.

The “ferros” of MAPbI3: ferroelectricity, ferroelasticity and its crystallographic foundations in hybrid halide perovskites

Abstract Hybrid halide perovskites have been identified as an important novel class of photovoltaic absorbers and have proven their great potential with ever record-breaking efficiencies. Some of the more fundamental properties of halide perovskites, however, still are to be properly understood. The ongoing debate as to whether ferroelectricity and/or ferroelasticity play a role in these materials is just one example for this. Herein, I aim to make these phenomena more approachable to the wider research community and elucidate the foundations and consequences of these phenomena.