Molecular Origin of Properties of Organic-Inorganic Hybrid Perovskites: The Big Picture from Small Clusters

Beyond Shell-Filling: Strong Enhancement of Electron Affinity of Metal Clusters through a Noninvasive Oriented External Electric Field

Traditional electron counting rules, like the Jellium model, have long been successfully utilized in designing superhalogens by modifying clusters to have one electron less than a filled electronic shell. However, this shell-filling approach, which involves altering the intrinsic properties of the clusters, can be complex and challenging to control, especially in experiments. In this letter, we theoretically establish that the oriented external electric field (OEEF) can substantially enhance the electron affinity (EA) of diverse aluminum-based metal clusters with varying valence electron configurations, leading to the creation of superhalogen species without altering their shell arrangements. This OEEF approach offers a noninvasive alternative to traditional superatom design strategies, as it does not disrupt the clusters' geometrical structures and superatomic states. These findings contribute a vital piece to the puzzle of constructing superalkalis and superhalogens, extending beyond conventional shell-filling strategies and potentially expanding the range of applications for functional clusters.

Strongly Bound Polynuclear Anions Comprising Scandium Fluoride Building Blocks

The stability of polynuclear anions composed of ScF3 building blocks was studied by using ab initio and density functional theory electronic structure methods and flexible basis sets. Thorough exploration of ground state potential energy surfaces of (Sc2F7)-, (Sc3F10)-, and (Sc4F13)- anions which may be viewed as comprising ScF3 fragments and the additional fluorine atom led to determining the isomeric structures thereof. It was found that the most stable isomers which are predicted to dominate at room temperature correspond to the compact structures enabling the formation of a large number of Sc-F-Sc bridging linkages rather than to the chain-like structures. The vertical electron detachment energies of the (ScnF3n+1)- anions were found to be very large (spanning the 10.85-12.29 eV range) and increasing with the increasing number of scandium atoms (n) and thus the ScF3 building blocks involved in the structure. Thermodynamic stability of (ScnF3n+1)- anions (i.e., their susceptibility to fragmentation) was also verified and discussed.

Small practical cluster models for perovskites based on the similarity criterion of central location environment and their applications

Developing universal theoretical models for perovskites (often denoted as ABX₃) can contribute to the rational design of novel perovskite photovoltaic materials. However, few models can be successfully applied to study the intrinsic electronic structure due to the poor accuracy and unaffordable computational cost. Herein, we report the innovative construction of small practical cluster models through the similarity criterion of the central location environment, which retains only the central A-site as the original cation while the others are substituted by Cs to keep the clusters electrically neutral. The central cation has a chemical environment similar to that of the bulk perovskite. The binding energy between A and the BX framework, geometric structures (B-X distances and B-X-B angles), and the electronic structures (the gap and the spatial distribution of HOMO and LUMO, electron distribution) of these clusters have been investigated and compared with the corresponding properties of bulk materials. The results suggest that the cluster model with twelve B-atoms suitably describes these properties. The geometric structures and gaps are closer to the bulk situations than the quasi-one-dimensional and quasi-two-dimensional cluster models with all-primitive cations, respectively. Other organic cations, such as NH₃(CH₂)_nCH₃ (n = 1, 2, and 3 for EA, PA, and BA, respectively), and (NH₂)₂CH (FA) can, therefore, mimic perovskite materials. Clusters with different sizes of A indicate that PA and BA will distort the quasi-cubic structures, which is consistent with the judgment of the tolerance factor of bulk materials. The reliable cluster model provides the research foundation for some basic issues of perovskites, such as vibrational spectroscopy and hydrogen bonding strength, to gain detailed insight into the interactions between A and the BX framework.

A descriptor for the structural stability of organic-inorganic hybrid perovskites based on binding mechanism in electronic structure

The poor stability of organic-inorganic hybrid perovskites hinders its commercial application, which motivates a need for greater theoretical insight into its binding mechanism. To date, the binding mode of organic cation and anion inside organic-inorganic hybrid perovskites is still unclear and even contradictory. Therefore, in this work based on density functional theory (DFT), the binding mechanism between organic cation and anion was systematically investigated through electronic structure analysis including an examination of the electronic localization function (ELF), electron density difference (EDD), reduced density gradient (RDG), and energy decomposition analysis (EDA). The binding strength is mainly determined by Coulomb effect and orbital polarization. Based on the above analysis, a novel 2D linear regression descriptor that E_b =  - 9.75Q²/R₀ + 0.00053 V∙E_HL - 6.11 with coefficient of determination R² = 0.88 was proposed to evaluate the binding strength (the units for Q, R₀, V, and E_HL are |e|, Å, bohr³, and eV, respectively), revealing that larger Coulomb effect (Q²/R₀), smaller volume of perovskite (V), and narrower energy difference (E_HL) between the lowest unoccupied molecular orbital (LUMO) of organic cation and the highest occupied molecular orbital (HOMO) of anion correspond to the stronger binding strength, which guides the design of highly stable organic-inorganic hybrid perovskites.

Antiperovskite Electrolytes for Solid-State Batteries

Solid-state batteries have fascinated the research community over the past decade, largely due to their improved safety properties and potential for high-energy density. Searching for fast ion conductors with sufficient electrochemical and chemical stabilities is at the heart of solid-state battery research and applications. Recently, significant progress has been made in solid-state electrolyte development. Sulfide-, oxide-, and halide-based electrolytes have been able to achieve high ionic conductivities of more than 10^-3 S/cm at room temperature, which are comparable to liquid-based electrolytes. However, their stability toward Li metal anodes poses significant challenges for these electrolytes. The existence of non-Li cations that can be reduced by Li metal in these electrolytes hinders the application of Li anode and therefore poses an obstacle toward achieving high-energy density. The finding of antiperovskites as ionic conductors in recent years has demonstrated a new and exciting solution. These materials, mainly constructed from Li (or Na), O, and Cl (or Br), are lightweight and electrochemically stable toward metallic Li and possess promising ionic conductivity. Because of the structural flexibility and tunability, antiperovskite electrolytes are excellent candidates for solid-state battery applications, and researchers are still exploring the relationship between their structure and ion diffusion behavior. Herein, the recent progress of antiperovskites for solid-state batteries is reviewed, and the strategies to tune the ionic conductivity by structural manipulation are summarized. Major challenges and future directions are discussed to facilitate the development of antiperovskite-based solid-state batteries.

Influence of Different Rotations of Organic Formamidinium Molecule on Electronic and Optical Properties of FAPbBr3 Perovskite

Hybrid organic–inorganic halide perovskites (HOIPs) have recently represented a material breakthrough for optoelectronic applications. Obviously, studying the interactions between the central organic cation and the Pb-X inorganic octahedral could provide a better understanding of HOIPs. In this work, we used a first-principles theoretical study to investigate the effect of different orientations of central formamidinium cation (FA+) on the electronic and optical properties of FAPbBr3 hybrid perovskite. In order to do this, the band structure (with and without spin–orbit coupling (SOC)), density of states (DOS), partial density of states (PDOS), electron density, distortion index, bond angle variance, dielectric function, and absorption spectra were computed. The findings revealed that a change in the orientation of FA+ caused some disorders in the distribution of interactions, resulting in the formation of some specific energy levels in the structure. The interactions between the inorganic and organic parts in different directions create a distortion index in the bonds of the inorganic octahedral, thus leading to a change in the volume of PbBr6. This is the main reason for the variations observed in the electronic and optical properties of FAPbBr3. The obtained results can be helpful in solar-cell applications.

A new perspective for evaluating the photoelectric performance of organic-inorganic hybrid perovskites based on the DFT calculations of excited states

The high efficiency of organic-inorganic hybrid perovskites has attracted the attention of many scholars all over the world, the chemical formula of which is ABX3, where A is an organic cation, B is a metal cation, and X is a halogen ion. In addition, the micro-mechanism behind the efficient photoelectric conversion needs more in-depth exploration. Therefore, in this work, based on time-dependent density functional theory (TD-DFT), the electron transfer mechanism from the ground state to the first singlet excited state was systematically investigated by electron and hole analysis and an inter-fragment charge transfer amount method (IFCT). In this work, we optimized and analyzed 99 different perovskite cluster configurations, where A sites are CH3NH3+ (MA+), NH2CHNH2+ (FA+), CH3CH2NH3+ (EA+), NH2CHOH+ (JA+), NH3OH+ (BA+), N(CH3)4+ (DA+), CH3CH2CH2NH3+ (KB+), CH3CH2CH2CH2NH3+ (KC+), C3N2H5+ (RA+), CH(CH3)2+ (TA+), and CH3NH(CH3)2+ (UA+), B sites are Ge2+, Sn2+ and Pb2+, and X sites are Cl-, Br- and I-. According to the analysis of a series of perovskite clusters of the hole-electron distribution, the distribution is mainly concentrated on BX, and electrons and holes are respectively distributed on B and X sites. The exciton binding energy decreases when the metal element changes from Ge to Pb and the halogen element changes from Cl to I. A radar chart including the exciton binding energy, excited energy, amount of net charge transfer, electron and hole overlap index, distance between the centroid of holes and electrons, and the hole and electron separation index was proposed to intuitively describe the electron transmission characteristics of perovskites. Based on that, a comprehensive score index was innovatively proposed to evaluate the photoelectric property of perovskites, providing foundational guidance for the design of high-efficiency organic-inorganic hybrid perovskites.

Tripodal Podand Ligand with a Superhalogen Nature as an Effective Molecular Trap

Tris(2-methoxyethyl) fluoroborate anion (TMEFA), anovel tripodal ligand based on the BF4− superhalogen anion, is proposed and was investigated theoretically using ab initio MP2 (second-order Møller-Plesset perturbational method) and OVGF (outer valence Green function) methods. The studied molecule comprises three 2-methoxyethoxy groups (-O-CH2-CH2-O-CH3) connected to a central boron atom, which results in the C3-symmetry of the compound. The resulting anion was stable against fragmentation processes and its vertical electron detachment energy was found to be 5.72 eV. Due to its equilibrium structure resembling that of classical tripodal podands, the [F-B(O-CH2-CH2-O-CH3)3]− anion is capable of binding metal cations using its three arms, and thus may form strongly bound ionic complexes such as [F-B(O-CH2-CH2-O-CH3)3]−/Li+ and [F-B(O-CH2-CH2-O-CH3)3]−/Mg2+. The binding energies predicted for such compounds far exceed those of the similar neutral classical podand ligands, which likely makes the [F-B(O-CH2-CH2-O-CH3)3]− system a more effective molecular trap or steric shielding agent with respect to selected metal cations.

Boosting Photovoltaic Performance and Stability of Super-Halogen-Substituted Perovskite Solar Cells by Simultaneous Methylammonium Immobilization and Vacancy Compensation

Perovskite solar cells (PSCs) are susceptible to intrinsic structural instability associated with the presence of inorganic halide anions and organic cation vacancies, thus leading to the deterioration or even premature failure of devices. Herein, we develop an efficient strategy using super-halogen BH₄^- substitution to simultaneously immobilize methylammonium and substitute iodide vacancy for high-performance PSCs based on the dihydrogen bonding interactions. The introduced super-halogen BH₄^- groups not only significantly reduce the vacancy density but also effectively inhibit the decomposition of the CH₃NH₃⁺ group by forming perovskite CH₃NH₃PbI_3-x(BH₄^-)_x. The power conversion efficiency (PCE) of the assembled mesoporous devices is remarkably promoted from 18.43 to 21.10%, accompanied by significant increase of both J_sc and V_oc without obvious hysteresis. The superior PSCs can retain 90 and 80% of their initial PCE even after being stored for 1200 h under environmental conditions (50 ± 10% RH) and 240 h at 85 °C in the dark, respectively. Moreover, it delivers excellent optical stability under ultraviolet illumination. This work provides an avenue to improve both the long-term stability and photovoltaic performance of PSCs.

Tuning the Electronic Properties and Performance of Low-Temperature CO Oxidation of the Gold Cluster by Oriented External Electronic Field

Conventional electronic rules, including Jellium and Wade-Mingos rules and so on, have long been successfully dedicated to design superatoms. These rules, however, rely on altering the intrinsic properties, for example, the compositions or the number of valence electrons, of clusters, which is relatively complicated and inconvenient to manipulate, especially in experiments. Herein, by employing density functional theory calculations, the oriented external electric field (OEEF) was demonstrated to possess the capability of precisely and continuously regulating the electronic properties of clusters at will, representing a novel and noninvasive methodology in constructing stable superatoms because it hardly changes the geometries of clusters. More interestingly, the active sites formed by the charge redistribution upon the introduction of an OEEF could significantly promote the catalytic performance of the low-temperature CO oxidation over clusters. Considering the convenient source of the OEEF, the findings highlighted here may boost the potential applications of superatom-assembly nanomaterials in catalysis and materials science.

Theoretical study on the stability of the complexes A···BX3 [A = CH3NH3+, NH2CHNH2+, NH2CHOH+; B = Sn2+, Pb2+; X = F-, Cl-, Br-, I-]

The interaction of corresponding molecular building blocks of the complexes A···BX₃ would provide valuable information to quickly estimate the properties of the solar cell. In this work, the H···X hydrogen bond between the organic cations A⁺ (CH₃NH₃⁺, NH₂CHNH₂⁺, NH₂CHOH⁺) and the inorganic anions BX₃^- (B = Sn²⁺, Pb²⁺, X = F^-, Cl^-, Br^-, I^-) were studied by theoretical calculation at the B3LYP-D3/ma-def2-TZVP level to investigate the stability of the complexes A···BX₃. The strength of H···X hydrogen bond is enhanced in the order of NH₂CHNH₂⁺ < CH₃NH₃⁺ < NH₂CHOH⁺, Sn²⁺ < Pb²⁺, and weakened in the order of F^- > Cl^- > Br^- > I^-, indicating that the complexes A···BX₃ enhances with the increase of electron donating ability of B and the decrease of electron donating ability of X, and application of the substituent A = NH₂CHOH⁺ may be effective to enhance the stability of perovskite and replace the toxic metal Pb by Sn. Graphical abstract.

Building Better Batteries in the Solid State: A Review

Most of the current commercialized lithium batteries employ liquid electrolytes, despite their vulnerability to battery fire hazards, because they avoid the formation of dendrites on the anode side, which is commonly encountered in solid-state batteries. In a review two years ago, we focused on the challenges and issues facing lithium metal for solid-state rechargeable batteries, pointed to the progress made in addressing this drawback, and concluded that a situation could be envisioned where solid-state batteries would again win over liquid batteries for different applications in the near future. However, an additional drawback of solid-state batteries is the lower ionic conductivity of the electrolyte. Therefore, extensive research efforts have been invested in the last few years to overcome this problem, the reward of which has been significant progress. It is the purpose of this review to report these recent works and the state of the art on solid electrolytes. In addition to solid electrolytes stricto sensu, there are other electrolytes that are mainly solids, but with some added liquid. In some cases, the amount of liquid added is only on the microliter scale; the addition of liquid is aimed at only improving the contact between a solid-state electrolyte and an electrode, for instance. In some other cases, the amount of liquid is larger, as in the case of gel polymers. It is also an acceptable solution if the amount of liquid is small enough to maintain the safety of the cell; such cases are also considered in this review. Different chemistries are examined, including not only Li-air, Li-O2, and Li-S, but also sodium-ion batteries, which are also subject to intensive research. The challenges toward commercialization are also considered.

Significance of hydrogen bonding and other noncovalent interactions in determining octahedral tilting in the CH3NH3PbI3 hybrid organic-inorganic halide perovskite solar cell semiconductor

The CH₃NH₃PbI₃ (methylammonium lead triiodide) perovskite semiconductor system has been viewed as a blockbuster research material during the last five years. Because of its complicated architecture, several of its technological, physical and geometrical issues have been examined many times. Yet this has not assisted in overcoming a number of problems in the field nor in enabling the material to be marketed. For instance, these studies have not clarified the nature and type of hydrogen bonding and other noncovalent interactions involved; the origin of hysteresis; the actual role of the methylammonium cation; the nature of polarity associated with the tetragonal geometry; the unusual origin of various frontier orbital contributions to the conduction band minimum; the underlying phenomena of spin-orbit coupling that causes significant bandgap reduction; and the nature of direct-to-indirect bandgap transition features. Arising from many recent reports, it is now a common belief that the I···H–N interaction formed between the inorganic framework and the ammonium group of CH₃NH₃⁺ is the only hydrogen bonded interaction responsible for all temperature-dependent geometrical polymorphs of the system, including the most stable one that persists at low-temperatures, and the significance of all other noncovalent interactions has been overlooked. This study focussed only on the low temperature orthorhombic polymorph of CH₃NH₃PbI₃ and CD₃ND₃PbI₃, where D refers deuterium. Together with QTAIM, DORI and RDG based charge density analyses, the results of density functional theory calculations with PBE with and without van der Waals corrections demonstrate that the prevailing view of hydrogen bonding in CH₃NH₃PbI₃ is misleading as it does not alone determine the a⁻b⁺a⁻ tilting pattern of the PbI₆⁴⁻ octahedra. This study suggests that it is not only the I···H/D–N, but also the I···H/D–C hydrogen/deuterium bonding and other noncovalent interactions (viz. tetrel-, pnictogen- and lump-hole bonding interactions) that are ubiquitous in the orthorhombic CH₃NH₃PbI₃/CD₃ND₃PbI₃ perovskite geometry. Their interplay determines the overall geometry of the polymorph, and are therefore responsible in part for the emergence of the functional optical properties of this material. This study also suggests that these interactions should not be regarded as the sole determinants of octahedral tilting since lattice dynamics is known to play a critical role as well, a common feature in many inorganic perovskites both in the presence and the absence of the encaged cation, as in CsPbI₃/WO₃ perovskites, for example.

Revealing the Chemistry between Band Gap and Binding Energy for Lead-/Tin-Based Trihalide Perovskite Solar Cell Semiconductors

A relationship between reported experimental band gaps (solid) and DFT-calculated binding energies (gas) is established, for the first time, for each of the four ten-membered lead (or tin) trihalide perovskite solar cell semiconductor series examined in this study, including CH₃ NH₃ PbY₃ , CsPbY₃ , CH₃ NH₃ SnY₃ and CsSnY₃ (Y=I_(3-x) Br_x=1-3 , I_(3-x) Cl_x=1-3 , Br_(3-x) Cl _x=1-3 , and IBrCl). The relationship unequivocally provides a new dimension for the fundamental understanding of the optoelectronic features of solid-state solar cell thin films by using the 0 K gas-phase energetics of the corresponding molecular building blocks.

Li-rich antiperovskite superionic conductors based on cluster ions

Enjoying great safety, high power, and high energy densities, all-solid-state batteries play a key role in the next generation energy storage devices. However, their development is limited by the lack of solid electrolyte materials that can reach the practically useful conductivities of 10^-2 S/cm at room temperature (RT). Here, by exploring a set of lithium-rich antiperovskites composed of cluster ions, we report a lithium superionic conductor, Li₃SBF₄, that has an estimated 3D RT conductivity of 10^-2 S/cm, a low activation energy of 0.210 eV, a giant band gap of 8.5 eV, a small formation energy, a high melting point, and desired mechanical properties. A mixed phase of the material, Li₃S(BF₄)_0.5Cl_0.5, with the same simple crystal structure exhibits an RT conductivity as high as 10^-1 S/cm and a low activation energy of 0.176 eV. The high ionic conductivity of the crystals is enabled by the thermal-excited vibrational modes of the cluster ions and the large channel size created by mixing the large cluster ion with the small elementary ion.

Precise Composition Tailoring of Mixed-Cation Hybrid Perovskites for Efficient Solar Cells by Mixture Design Methods

Mixed anion/cation perovskites absorber has been recently implemented to construct highly efficient single junction solar cells and tandem devices. However, considerable efforts are still required to map the composition-property relationship of the mixed perovskites absorber, which is essential to facilitate device design. Here we report the intensive exploration of mixed-cation perovskites in their compositional space with the assistance of a rational mixture design (MD) methods. Different from the previous linear search of the cation ratios, it is found that by employing the MD methods, the ternary composition can be tuned simultaneously following simplex lattice designs or simplex-centroid designs, which enable significantly reduced experiment/sampling size to unveil the composition-property relationship for mixed perovskite materials and to boost the resultant device efficiency. We illustrated the composition-property relationship of the mixed perovskites in multidimension and achieved an optimized power conversion efficiency of 20.99% in the corresponding device. Moreover, the method is demonstrated to be feasible to help adjust the bandgap through rational materials design, which can be further extended to other materials systems, not limited in polycrystalline perovskites films for photovoltaic applications only.

Atomic-Level Design of Water-Resistant Hybrid Perovskites for Solar Cells by Using Cluster Ions

Organic-inorganic hybrid perovskites have emerged as the most promising material in the development of next-generation solar cells. However, the stability of these materials exemplified by CH₃NH₃PbI₃ is the most pressing challenge; it readily decomposes when exposed to moisture. Here, we show how one can use a particular type of cluster ions, known as pseudohalides, to enhance the water resistance of the hybrid perovskite, while maintaining its favorable electronic properties. Starting with a simple physical model, we propose a new class of water-resistant hybrid perovskites as solar-cell absorbers based on the cluster ions by using DFT calculations and ab initio molecular dynamics. Limitations of applying the currently known pseudohalides for our purpose are also discussed.

Does the endohedral borospherene supersalt FLi2@B39maintain the “super” properties of its subunits?

The behavior of the entirely unique system represented by superalkaline species incorporated into a superhalogen cage has been studied using density functional theory. The calculations revealed that superhalogen and superalkaline properties inherent in the separated fragments are lost in FLi₂@B₃₉complexes.

Tuning the gap of lead-based halide perovskites by introducing superalkali species at the cationic sites of ABX3-type structure

New perovskites are formed by introducing polyatomic yet aprotic superalkali species at the cationic A-sites of the ABX₃ structure.

Oxidizing CO2 with superhalogens

The Sb₃F₁₆ species was found to be capable of ionizing the CO₂ molecule.

Role of ligands in the stability of BnXn and CBn−1Xn (n = 5–10; X = H, F, CN) and their potential as building blocks of electrolytes in lithium ion batteries

We predict a series of boron-cage-based stable (di-)anions, and demonstrate them to be high-performance electrolytes in Li-ion batteries.

Superhalogens as building blocks of two-dimensional organic-inorganic hybrid perovskites for optoelectronics applications

Organic-inorganic hybrid perovskites, well known for their potential as the next generation solar cells, have found another niche application in optoelectronics. This was demonstrated in a recent experiment (L. Dou, et al., Science, 2015, 349, 1518) on atomically thin (C₄H₉NH₃)₂PbBr₄, where, due to quantum confinement, the bandgap and the exciton binding energy are enhanced over their corresponding values in the three-dimensional bulk phase. Using density functional theory we show that when halogen atoms (e.g. I) are sequentially replaced with superhalogen molecules (e.g. BH₄) the bandgap and exciton binding energy increase monotonically with the superhalogen content with the exciton binding energy of (C₄H₉NH₃)₂Pb(BH₄)₄ approaching the value in monolayer black phosphorus. Lead-free admixtures (C₄H₉NH₃)₂MI_4-x(BH₄)_x (M = Sn and Ge; x = 0-4) also show a similar trend. Thus, a combination of quantum confinement and compositional change can be used as an effective strategy to tailor the bandgap and the exciton binding energy of two-dimensional hybrid perovskites, making them promising candidates for optoelectronic applications.

Reactivity of Two-Dimensional Au9, Pt9, and Au18Pt18 against Common Molecules

Adsorption of common molecules over two-dimensional Au9, Pt9, and Au18Pt18 is investigated with implementation of first-principles calculations. In general, it is found that Pt9 and Au18Pt18 exhibit low adsorption energies where Au18Pt18 preserves the structural integrity of the molecule and surface. In particular, adsorption of molecules onto Au18Pt18 frequently results in low adsorption energies and high reactivity with minor surface reconstruction of Au18Pt18 and average bond lengths of molecules. The decrease in adsorption energy can be attributed to the presence of platinum, while gold can be considered responsible for structural stability. In addition, molecule dissociation is observed in the cases of H2, HCl, CH4, SO, and SO2 when Pt atoms are involved. Thus, two-dimensional Au9, Pt9, and Au18Pt18 show low adsorption energies against common molecules, reflecting adsorption energies observed in small Au and Pt clusters. These results demonstrate that Au18Pt18 can successfully utilize the low adsorption energies associated with platinum while preserving the integrity of the surface structure using gold atoms, making it possible to adsorb desired molecules using select areas of the Au18Pt18 surface.

Complex metal borohydrides: multifunctional materials for energy storage and conversion

With the limited supply of fossil fuels and their adverse effect on the climate and the environment, it has become a global priority to seek alternate sources of energy that are clean, abundant, and sustainable. While sources such as solar, wind, and hydrogen can meet the world's energy demand, considerable challenges remain to find materials that can store and/or convert energy efficiently. This topical review focuses on one such class of materials, namely, multi-functional complex metal borohydrides that not only have the ability to store sufficient amount of hydrogen to meet the needs of the transportation industry, but also can be used for a new generation of metal ion batteries and solar cells. We discuss the material challenges in all these areas and review the progress that has been made to address them, the issues that still need to be resolved and the outlook for the future.

Structural and electronic features of small hybrid organic–inorganic halide perovskite clusters: a theoretical analysis

We herein present the results of a series of calculations performed on some representative cluster models of hybrid organic–inorganic halide perovskites, (MA)_jPb_kX_l (l = 2j + k; MA = methylammonium, ⁺CH₃NH₃; X = halide).