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One of the crucial metabolic processes for both plant and animal kingdoms is the oxidation of the amino acid tryptophan (TRP) that regulates plant growth and controls hunger and sleeping patterns in animals. Here, we report revolutionary insights into how this process can be crucially affected by interactions with metal oxide nanoparticles (NPs), creating a toolbox for a plethora of important biomedical and agricultural applications. Molecular mechanisms in TRP–NP interactions were revealed by NMR and optical spectroscopy for ceria and titania and by X-ray single-crystal study and a computational study of model TRP–polyoxometalate complexes, which permitted the visualization of the oxidation mechanism at an atomic level. Nanozyme activity, involving concerted proton and electron transfer to the NP surface for oxides with a high oxidative potential, like CeO2or WO3, converted TRP in the first step into a tricyclic organic acid belonging to the family of natural plant hormones, auxins. TiO2, a much poorer oxidant, was strongly binding TRP without concurrent oxidation in the dark but oxidized it nonspecifically via the release of reactive oxygen species (ROS) in daylight.

Water-in-salt electrolytes (WISEs) have expanded the useful electrochemical stability of water, making the development of functional aqueous lithium-ion batteries more accessible. The implementation of additives in the formulation of WISEs can further improve the electrochemical stability of water and avoid potential lithium-ion salt solubility issues. Here, we have used Gemini-type ionic liquids to suppress water activity by designing the structure of ionic-liquid cations. The different water-organizing effects of ionic-liquid cations have been investigated and correlated to battery performance in LTO/LMO full cells. The champion device, containing the most chaotropic ionic liquid, retained at least 99% of its Coulombic efficiency after 500 charging cycles, associated with a final specific discharge capacity of 85 mA h·g–1. These results indicated that water-rich Li+solvation shells significantly contribute to the excellent device performance and long-term stability of the LTO/LMO-based full battery cells. This work shows that the fine-tuning of the Li+solvation shell and water structure by the addition of chaotropic cations represents a promising strategy for generating more stable and effective lithium-ion-containing rechargeable aqueous batteries.

OO bond formation between O5 and W2 in the non-rearranged oxygen-evolving complex has quite high barriers, and thus structural rearrangement during the catalytic cycle is necessary to facilitate their coupling.

A low-cost, crosslinked, 3D polymer P65has been designed and synthesized as a dopant-free hole-transport material for application in efficient and stable n-i-p type perovskite solar cells.

Low-dimensional hybrid perovskite materials offer significantly improved stability as well as an extensive compositional space to explore. However, they suffer from poor photovoltaic performance as compared to the 3D perovskite materials because of poor charge-transport properties. Herein, we present the concept of internal dye-sensitized hybrid perovskite compounds involving five novel low-dimensional perovskite-type materials 1–5incorporating triarylmethane, phenazinium and near-infrared (NIR) cyanine cationic dyes, respectively. The synthesis characterization and theoretical analysis of these compounds are presented. Theoretical calculations provide interesting insights into the effects of these dyes on the band structure of the low-dimensional anionic metal-halides and especially highlight compound 1as a promising photovoltaic candidate. Solar cell investigation of devices based on 1were conducted. The results show an average power conversion efficiency (PCE) of about 0.1%, which is among the highest reported for a 1D material despite the use of undoped Spiro-OMeTAD as the hole-transport material (HTM). Incident photon-to-electron efficiency (IPCE) spectra confirm the contribution of the dye to the overall photocurrent of the solar cell. Moreover, examination of solar cell devices based on the bismuth-based compound 5resulted in PCEs in the range of 0.1%. This illustrates the potential of this concept to be exploited for lead-free photovoltaics. Finally automated robotized screening of low-dimensional hybrid perovskite materials through the screening robot PROTEUS has emerged as a powerful tool in the search for novel perovskite-like materials. Our work highlights that the use of cationic dyes could induce interesting sensitizing properties to low-dimensional metal-halide chains and may therefore provide inspiration and new design strategies for the synthesis of new lead-free photovoltaic materials

Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo[1,2-b:4,5-b’]dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor–acceptor (D–A) structure. Herein, a new class of phenanthrocarbazole (PC)-based polymeric HTMs (PC1, PC2, and PC3) has been synthesized by inserting a PCunit into a polymeric thiophene or selenophene chain with the aim of enhancing the π–π stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the PC. Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing PC3as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the “Lewis soft” selenium atom can passivate surface trap sites of perovskite films by Pb–Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs.

The ways to overcome surface charge recombination and poor interface contact are still the central challenges for the development of inorganic–organic hybrid halide perovskite solar cells (PSCs). [6,6]-Phenyl C61butyric acid methyl ester (PCBM) is commonly employed in PSCs, but it has some disadvantages including high charge recombination and poor surface coverage. Therefore, the addition of an interfacial engineering layer showing efficient surface passivation, electron extraction, and excellent interface contact can solve the above problems. Furthermore, by employing interface engineering with a spike structure of the energy levels, the reduced energy losses are beneficial to elevating the open-circuit voltage (Voc) in PSCs. Herein, the linear naphthalene imide dimer containing an indacenodithiophene unit (IDTT2NPI) has been developed as an excellent interface engineering material to strengthen the perovskite performance. The introduction of a spike interface on the top of a methylammonium lead triiodide (MAPbI3) film resulted in a high Vocof 1.12 V with the optimal efficiency reaching 20.2%. The efficiency enhancement can be traced to the efficient surface passivation and enhanced interface contact. The mechanism of IDTT2NPI as the interface engineering layer was investigated by both experiments and theoretical calculations. This work provides a promising naphthalene imide-based interfacial material for high-efficiency and stable PSCs.

Despite the ubiquity and importance of organic hole-transport materials in photovoltaic devices, their intrinsic low conductivity remains a drawback. Thus, chemical doping is an indispensable solution to this drawback and is essentially always required. The most widely used p-type dopant, FK209, is a cobalt coordination complex. By reducing Co(III) to Co(II), Spiro-OMeTAD becomes partially oxidized, and the film conductivity is initially increased. In order to further increase the conductivity, the hygroscopic co-dopant LiTFSI is typically needed. However, lithium salts are normally quite hygroscopic, and thus, water absorption has been suggested as a significant reason for perovskite degradation and therefore limited device stability. In this work, we report a LiTFSI-free doping process by applying organic salts in relatively high amounts. The film conductivity and morphology have been studied at different doping amounts. The resulting solar cell devices show comparable power conversion efficiencies to those based on conventional LiTFSI-doped Spiro-OMeTAD but show considerably better long-term device stability in an ambient atmosphere.

We utilize herein ultrafast mid-infrared probe laser pulses to explore the mechanism for the charge recombination/trapping process of photogenerated charges within the band gap of TiO2and across interfaces. Low-energy photons solely probe the free electrons present in the conduction band of TiO2and those captured in shallow-trap states. We found that >70% of the photogenerated charges disappear from the conduction band in the first few nanoseconds due to electron trapping followed by charge recombination at longer time scales. Moreover, the behavior of the dynamics of the free electrons within the band gap of TiO2and electrons generated at the interface of adsorbed organic dyes was investigated and compared. This comparison shows that the main driving force for the efficient charge trapping of photogenerated charges within the picosecond time scale is the presence of photogenerated holes, within the band gap of TiO2, or close to the interface of TiO2. If the hole is far from the TiO2surface, the electron trapping process is hindered, and almost 100% of photogenerated charges can survive up to nanoseconds. This work offers a deeper understanding of the charge trapping and charge recombination processes, by knowing the spatial hole effect, in TiO2and similar semiconductors upon utilization in photonic devices and photocatalysis.

Perovskite solar cells (PSCs) has skyrocketed in the past decade to an unprecedented level due to their outstanding photoelectric properties and facile processability. However, the utilization of expensive hole transport materials (HTMs) and the inevitable instability instigated by the deliquescent dopants represent major concerns hindering further commercialization. Here, a series of low-cost, conjugated polymers are designed and applied as dopant-free HTMs in PSCs, featuring tuned energy levels, good temperature and humidity resistivity, and excellent photoelectric properties. Further studies highlight the critical and multifaceted roles of the polymers with respect to facilitating charge separation, passivating the surface trap sites of perovskite materials, and guaranteeing long-term stability of the devices. A stabilized power conversion efficiency (PCE) of 20.3% and remarkably enhanced device longevity are achieved using the dopant-free polymer P3with a low concentration of 5 mg/mL, qualifying the device as one of the best PSC systems constructed on the basis of dopant-free HTMs so far. In addition, the flexible PSCs based on P3also exhibit a PCE of 16.2%. This work demonstrates a promising route toward commercially viable, stable, and efficient PSCs.

Organic thin-film solar cells have demonstrated a bright prospect for commercial applications, where organic photosensitizers act as the most important kernel. In the global motif of sustainable development, unrelenting research efforts have been devoted to the exploration of organic material containing photosensitizers to achieve low-cost conversion of solar energy to clean electricity. In this work, two star-shaped donor cores, T1and T2, which consist of fused thiophene triazatruxene, have been synthesized and applied in two different types of solar cells. The two-dimensional π-bonded extension enhances their electron-donating capability and induces relatively strong intermolecular π–π stacking. The C3hsymmetrical donor isomers, featuring planar backbones and three-dimensional structures, are found to contribute toward a promising prospect for overall photoelectric applications.

Due to ligand scrambling, the synthesis and investigation of the properties of heteroleptic Cu(I) complexes can be a challenging task. In this work, we have studied the optical and electrochemical properties of a series of homoleptic complexes, such as [Cu(dbda)2]+, [Cu(dmp)2]+, [Cu(Br-dmp)2]+, [Cu(bcp)2]+, [Cu(dsbtmp)2]+, [Cu(biq)2]+, and [Cu(dap)2]+in solution, and those of their heteroleptics [Cu(dbda)(dmp)]+, [Cu(dbda)(Br-dmp)]+, [Cu(dbda)(bcp)]+, [Cu(dbda)(dsbtmp)]+, [Cu(dbda)(biq)]+, [Cu(dbda)(dap)]+adsorbed on the surface of anatase TiO2(dbda = 6,6′-dimethyl-2,2′-bipyridine-4,4′-dibenzoic acid; dmp = 2,9-dimethyl-1,10-phenanthroline; Br-dmp = 5-bromo-2,9-dimethyl-1,10-phenanthroline; bcp = bathocuproine or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline; dsbtmp = 2,9-di(sec-butyl)-3,4,7,8-tetramethyl-1,10-phenanthroline; biq = 2,2′-biquinoline; dap = 2,9-dianisyl-1,10-phenanthroline). We show that the maximum absorption wavelengths of the heteroleptic complexes on TiO2can be reasonably predicted from those of the homoleptic complexes in solution through a simple linear relation, whereas the prediction of their redox properties is less trivial. In the latter case, two different linear patterns emerge: one including the ligands bcp, biq, and dap and another one including the ligands dmp, Br-dmp, and dsbtmp. We offer an interpretation of the data based on the chemical structure of the ligands. On one hand, ligands bcp, biq, and dap possess a more extended π-conjugated system, which gives a more prominent contribution to the overall redox properties of the ligand dbda. On the other hand, the ligands dmp, Br-dmp, and dsbtmp are all phenanthroline-based containing alkyl substituents and contribute less than dbda to the overall redox properties.

Perovskite photovoltaics have recently attracted extensive attention due to their unprecedented high power conversion efficiencies (PCEs) in combination with primitive manufacturing conditions. However, the inherent polycrystalline nature of perovskite films renders an exceptional density of structural defects, especially at the grain boundaries (GBs) and film surfaces, representing a key challenge that impedes the further performance improvement of perovskite solar cells (PSCs) and large solar module ambitions towards commercialization. Here, a novel strategy is presented utilizing a simple ethylammonium chloride (EACl) additive in combination with a facile solvent bathing approach to achieve high quality methyammonium lead iodide (MAPbI3) films. Well-oriented, micron-sized grains were observed, which contribute to an extended carrier lifetime and reduced trap density. Further investigations unraveled the distinctively prominent effects of EACl in modulating the perovskite film quality. The EACl was found to promote the perovskite grain growing without undergoing the formation of intermediate phases. Moreover, the EACl was also revealed to deplete at relative low temperature to enhance the film quality without compromising the beneficial bandgap for solar cell applications. This new strategy boosts the power conversion efficiency (PCE) to 20.9% and 19.0% for devices with effective areas of 0.126 cm2and 1.020 cm2, respectively, with negligible current hysteresis and enhanced stability. Besides, perovskite films with a size of 10 × 10 cm2, and an assembled 16 cm2(5 × 5 cm2module) perovskite solar module with a PCE of over 11% were constructed.

A novel blue-colored organic donor-π-acceptor sensitizer, the so-called MKA16 dye, has been employed to construct solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2′,7-,7′-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9′-spirobifuorene (Spiro-OMeTAD) as hole-transport material, a good conversion efficiency of 5.8% was recorded for cells based on the MKA16 dye and a high photovoltage of 840 mV in comparison with 5.6% efficiency using the known (Dyenamo Blue) dye. By co-sensitization using the orange-colored D35 dye and MKA16 together, the solid-state solar cells showed an excellent efficiency of 7.5%, with a high photocurrent of 12.41 mA cm–2and open-circuit voltage of 850 mV. The results show that the photocurrent of ssDSSCs can be significantly improved by co-sensitization mainly attributed to the wider light absorption range contributing to the photocurrent. In addition, results from photo-induced absorption spectroscopy show that the dye regeneration is efficient in co-sensitized solar cells. The current results possible routes of improving the design of aesthetic and highly efficient ssDSSCs.

The main of this work is to overcome the drawbacks of the traditional fullerene derivatives used as electron transport materials (ETMs) for perovskite solar cells (PSCs). Herein, a new strategy to design non-fullerene ETMs is presented by molecular engineering to include charged moieties in the ETM. The designed ETM FA2+-PDI2is intrinsically ionic and the incorporated counter ions in FA2+-PDI2significantly increase the electron conductivity and improve the film formation properties. Through careful device optimization, PSCs based on the ionic ETM FA2+-PDI2exhibit an impressive average power conversion efficiency (PCE) of 17.0%, which is comparable to the PSC based on PC61BM (17.5%). The superior photovoltaic performance can be attributed to efficient electron extraction and effective electron transfer in the PSCs. This work provides important insights regarding the future design of new and efficient non-fullerene ETMs for PSCs.

Layered two-dimensional (2D) hybrid organic–inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in composition and dimensionality, and increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory calculations provide further details on the interaction and band gap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can be used to tune layered materials for optimal functionality and new applications.

A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D−π–A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pre-treatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2interface, leading us to formulate a hypothesis with respect to an electrolyte-induced dye reorganization at the surface.

Heterogeneous charge transfer processes at sensitized wide bandgap semiconductor surfaces are imperative for both fundamental knowledge and technical applications. Herein, we focus on the investigation of carrier dynamics of a triphenylamine-based dye, LEG4, sensitized TiO2(LEG4/TiO2) in contact with two types of electrolyte systems: pure cobalt-based electrolytes and in combination with an organic donor, tri(p-anisyl)amine (TPAA). Four different cobalt redox systems with potentials spanning a 0.3 V range were studied, and the carrier recombination and regeneration kinetics were monitored both at low and at high TiO2(e–) densities (1.3 × 1018and 1.3 × 1019cm–3, respectively). The results reveal that the introduction of the TPAA intermediate more effectively suppress the recombination loss of TiO2(e–) under high charge conditions, close to open-circuit, as compared to low charge conditions. As a result, the charge transfer from the cobalt complexes to the oxidized dyes is significantly improved by the addition of TPAA. Dye-sensitized solar cells fabricated with the TPAA-containing electrolytes demonstrate remarkable improvement in both VOCand JSCand lead to more than 25% increase of the light-to-electricity conversion efficiency. Furthermore, an unprecedented detrimental impact of TPAA on the device performance was identified when the redox potential of the TPAA donor and the cobalt complexes are close. This is ascribed to the formation of TPAA•+which can act as an active recombination centers and thus lower the solar cell performance. These insights point at a strategy to enhance the lifetimes of electrons generated in sensitized semiconductor electrodes by overcoming the charge recombination between TiO2and the oxidized dye under high carrier densities in the semiconductor substrate and offer practical guidance to the design of future efficient electrolyte systems for dye-sensitized solar cells.

Two D–A–D-structured hole-transport materials (YN1and YN2) have been synthesized and used in perovskite solar cells. The two HTMs have low-lying HOMO levels and impressive mobility. Perovskite-based solar cells (PSCs) fabricated with YN2showed a power conversion efficiency (PCE) value of 19.27% in ambient air, which is significantly higher than that of Spiro-OMeTAD(17.80%). PSCs based on YN1showed an inferior PCE of 16.03%. We found that the incorporation of the stronger electron-withdrawing group in the HTM YN2improves the PCE of PSCs. Furthermore, the YN2-based PSCs exhibit good long-term stability retaining 91.3% of its initial efficiency, whereas PSCs based on Spiro-OMeTADretained only 42.2% after 1000 h lifetime (dark conditions). These promising results can provide a new strategy for the design of D–A–D HTMs for PSC applications in future.

The reaction of CuCl2with 2,9-dimethyl-1,10-phenanthroline (dmp) does not lead to the formation of [Cu(dmp)2](Cl)2but instead to [Cu(dmp)2Cl]Cl, a 5-coordinated complex, in which one chloride is directly coordinated to the metal center. Attempts at removing the coordinated chloride by changing the counterion by metathesis were unsuccessful and resulted only in the exchange of the noncoordinated chloride, as confirmed from a crystal structure analysis. Complex [Cu(dmp)2Cl]PF6exhibits a reversible cyclic voltammogram characterized by a significant peak splitting between the reductive and oxidative waves (0.85 and 0.60 V vs NHE, respectively), with a half-wave potential E1/2= 0.73 V vs NHE. When reduced electrochemically, the complex does not convert into [Cu(dmp)2]+, as one may expect. Instead, [Cu(dmp)2]+is isolated as a product when the reduction of [Cu(dmp)2Cl]PF6is performed with l-ascorbic acid, as confirmed by electrochemistry, NMR spectroscopy, and diffractometry. [Cu(dmp)2]2+complexes can be synthesized starting from Cu(II) salts with weakly and noncoordinating counterions, such as perchlorate. Growth of [Cu(dmp)2](ClO4)2crystals in acetonitrile results in a 5-coordinated complex, [Cu(dmp)2(CH3CN)](ClO4)2, in which a solvent molecule is coordinated to the metal center. However, solvent coordination is associated with a dynamic decoordination–coordination behavior upon reduction and oxidation. Hence, the cyclic voltammogram of [Cu(dmp)2(CH3CN)]2+is identical to the one of [Cu(dmp)2]+, if the measurements are performed in acetonitrile. The current results show that halide ions in precursors to Cu(II) metal–organic coordination compound synthesis, and most likely also other multivalent coordination centers, are not readily exchanged when exposed to presumed strongly binding and chelating ligand, and thus special care needs to be taken with respect to product characterization.

The organization of dye molecules in the dye layer adsorbed on the semiconductor substrate in dye-sensitized solar cells has been studied using a combination of theoretical methods and experimental techniques. The model system is based on the simple D−π–A dye L0, which has been chemically modified by substituting the acceptor group CN with Br (L0Br) to offer better X-ray contrast. Experimental EXAFS data based on the Br K-edge backscattering show no obvious difference between dye-sensitized titania powder and titania film samples, thus allowing model systems to be based on powder slurries. Ab initio molecular dynamic (aiMD) calculations have been performed to extract less biased information from the experimental EXASF data. Using the aiMD calculation as input, the EXAFS structural models can be generated a priori that match the experimental data. Our study shows that the L0Br dye adsorbs in the trans-L0Br configuration and that adsorption involves both a proximity to other L0Br dye molecules and the titanium atoms in the TiO2substrate. These results indicate direct coordination of the dye molecules to the TiO2surface in contrast to previous results on metal–organic dyes. The molecular coverage of L0Br on mesoporous TiO2was also estimated using NICIS spectroscopy. The NICISS results emphasized that the L0Br dye on nanoporous titania mainly forms monolayers with a small contribution of multilayer coverage.

To develop new hole-transporting materials (HTMs) for efficient and stable perovskite solar cells (PSCs), 5,10,15,20-tetrakis{4-[N,N-di(4-methoxylphenyl)amino-phenyl]}-porphyrin was prepared in gram scale through the direct condensation of pyrrole and 4-[bis(4-methoxyphenyl)amino]benzaldehyde. Its Zn(II) and Cu(II) complexes exhibit excellent thermal and electrochemical stability, specifically a high hole mobility and very favorable energetics for hole extraction that render them a new class of HTMs in organometallic halide PSCs. As expected, ZnPas HTM in PSCs affords a competitive power conversion efficiency (PCE) of 17.78%, which is comparable to that of the most powerful HTM of Spiro-MeOTAD (18.59%) under the same working conditions. Meanwhile, the metal centers affect somewhat the photovoltaic performances that CuPas HTM produces a lower PCE of 15.36%. Notably, the PSCs employing ZnPshow a much better stability than Spiro-OMeTAD. Moreover, the two porphyrin-based HTMs can be prepared from relatively cheap raw materials with a facile synthetic route. The results demonstrate that ZnPand CuPcan be a new class of HTMs for efficient and stable PSCs. To the best of our knowledge, this is the best performance that porphyrin-based solar cells could show with PCE > 17%.

O2formation in photosystem II (PSII) is a vital event on Earth, but the exact mechanism remains unclear. The presently prevailing theoretical model is “radical coupling” (RC) involving a Mn(IV)-oxyl unit in an “open-cubane” Mn4CaO6cluster, which is supported experimentally by the S3state of cyanobacterial PSII featuring an additional Mn-bound oxygenic ligand. However, it was recently proposed that the major structural form of the S3state of higher plants lacks this extra ligand, and that the resulting S4state would feature instead a penta-coordinate dangler Mn(V)=oxo, covalently linked to a “closed-cubane” Mn3CaO4cluster. For this proposal, we explore here a large number of possible pathways of O–O bond formation and demonstrate that the “nucleophilic oxo–oxo coupling” (NOOC) between Mn(V)=oxo and μ3-oxo is the only eligible mechanism in such a system. The reaction is facilitated by a specific conformation of the cluster and concomitant water binding, which is delayed compared to the RC mechanism. An energetically feasible process is described starting from the valid S4state through the sequential formation of peroxide and superoxide, followed by O2release and a second water insertion. The newly found mechanism is consistent with available experimental thermodynamic and kinetic data and thus a viable alternative pathway for O2formation in natural photosynthesis, in particular for higher plants.

Perovskite solar cells (PSCs) have attracted significant interest and hole transporting materials (HTMs) play important roles in achieving high efficiency. Here, we report additive free ionic type HTMs that are based on 2-ethylhexyloxy substituted benzodithiophene (BDT) core unit. With the ionization of end-capping pyridine units, the hole mobility and conductivity of molecular materials are greatly improved. Applied in PSCs, ionic molecular material M7-TFSIexhibits the highest efficiency of 17.4% in the absence of additives [lithium bis(trifluoromethanesulfonyl)imide and 4-tert-butylpyridine]. The high efficiency is attributed to a deep highest occupied molecular orbital (HOMO) energy level, high hole mobility and high conductivity of M7-TFSI. Moreover, due to the higher hydrophobicity of M7-TFSI, the corresponding PSCs showed better stability than that of Spiro-OMeTAD based ones. In addition, the strong absorption and suitable energy levels of materials (M6, M7-Brand M7-TFSI) also qualify them as donor materials in organic solar cells (OSCs) and the devices containing M7-TFSIas donor material displayed an efficiency of 6.9%.

Two novel low-cost fluorene-based hole transport materials (HTMs) HT1and HT2as alternatives to the expensive HTM Spiro-OMeTADhave been designed and synthesized for the application in perovskite solar cells (PSCs) and solid-state dye-sensitized solar cell (ssDSCs). The two HTMs were prepared through a facile two-step reaction from cheap starting material and with a total yield higher than 90%. These HTMs exhibit good solubility and charge-transport ability. PSCs based on HT2achieved power conversion efficiency (PCE) of 18.04% under air conditions, which is comparable to that of the cell employing the commonly used Spiro-OMeTAD(18.27%), while HT1-based cell showed a slightly worse performance with a PCE of 17.18%. For ssDSCs, the HT2-based device yielded a PCE of 6.35%, which is also comparable to that of a cell fabricated based on Spiro-OMeTAD(6.36%). We found that the larger dimensional structure and molecular weight of HT2enable better photovoltaic performance than that of the smaller one HT1. These results show that easily synthesized fluorene-based HTMs have great potential to replace the expensive Spiro-OMeTADfor both PSCs and ssDSCs.

In this work, we have designed and synthesized a novel molecular material, BDT-C1, in which the core unit, benzodithiophene (BDT), was functionalized by thiophene (TP) and benzo-[c][1,2,5]-thiadiazole (BTZ) derivatives to generate extended π–conjugation. BDT-C1shows high hole mobility and high conductivity in its pristine form, in combination with appropriate energy level alignment with respect to [CH3NH3]PbI3and PC70BM, qualifying the material as a good candidate for application both in perovskite solar cells (PSCs) as dopant-free hole transport material (HTM) and in OSCs as donor material. The champion PSCs based on BDT-C1show an average conversion efficiency (PCE) of 13.4% (scan forward: 13.9%; scan backward: PCE=12.9%, scan rate: 10mV/s). Although the average efficiency obtained is slightly lower than that of reference devices based on the well-known doped HTM Spiro-OMeTAD (13.7%), the BDT-C1based devices exhibit better stability. Moreover, BDT-C1as a donor material in OSCs also shows good performance in combination with PC70BM as acceptor material, and an efficiency of 6.1% was obtained. The present results demonstrate that BDT-C1works well as both donor material in OSCs as well as dopant-free HTMs for efficient PSCs.

The current understanding on the behavior of nanoparticles in solution is limited. We have studied the effects of the aqueous environment on the anoxic oxidation of a Cu7nanoparticle using a range of different computational solvation models. On the basis of a series of hydroxylated Cu7(H2O)y(OH)xstructures, the performance of standard continuum models have been compared to discrete models including up to, and beyond, the second solvation layer. Both full quantum chemical (DFT: PBE0-D3) and QM/MM (PBE0/EFP1) computations were employed in the analysis. The Cu7structures were solvated in water nanodroplets and studied by molecular dynamics simulations. On the basis of the simulations, we were able to identify new modes of H2O interactions with the Cu7particle, modes that were previously considered unbeneficial. All solvation models favor the same equilibrium oxidation state corresponding to a Cu(I)OH surface species. However, for quantitative energy comparison of similar systems, our results suggest the use of a combined water cluster/continuum model including at least a first explicit solvation shell for energetic comparisons. Nevertheless, the second solvation shell is important for identifying representative inner solvation shell structures.

The electrolyte composition has a significant effect on the performance and stability of cobalt-based, dye-sensitized solar cells (DSSCs). The stability of DSSCs incorporating Co(II/III) tris(bipyridine) redox mediator has been investigated over 1000 h under full solar irradiation (with UV cutoff) at a temperature of 60 °C, the main focus being on monitoring the photovoltaic performance of the device and analyzing the internal charge-transfer dynamics in the presence of different cation coadditives (preferably added as tetracyanoborate salts). A clear cation-dependence is shown, not only of the early light-induced performance but also of the long-term photostability of the photovoltage of the device. These light-induced changes, which are attributed to the promotion of electron injection and less electron recombination loss, by transient spectral and electrochemical studies at the TiO2/dye/electrolyte interface, indicate that the main cation effects involve the TiO2surface electric field and energy-state distribution. By examining the stability of adsorbed and solvated dye during aging, it has been found that the dye photodegradation is probably responsible for the decline in the photovoltage and that this is extremely dependent on the nature of the cation coadditives in the electrolyte. It is therefore suggested that optimization of the electrolyte cation composition is essential for improving the stability of cobalt-based DSSCs.

Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule, hole transport material (HTM) POZ6-2using phenoxazine (POZ) as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction of a 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2exhibits good solubility in organic solvents. In addition, POZ6-2possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-free HTM in perovskite solar cells (PSCs) and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine (TBP) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMeTAD show an efficiency of 12.8%.

We applied organic donor-π-acceptor (D-π-A) sensitizers for photoelectrochemical polymerization (PEP) because of their appropriate energy levels and high light absorption. The polymerized conducting polymer PEDOT was used as hole conductor in all-solid-state dye-sensitized solar cells (ssDSCs). By combination of the D-π-A sensitizers and the generated PEDOT from PEP of bis-EDOT in acetonitrile, the resulting device showed an average power conversion efficiency of 5.6%. Furthermore, the PEP in aqueous micellar electrolytic medium was also employed because of the ability to decrease oxidation potential of the precursor, thereby making the polymerization process easier. The latter method is a cost-effective and environmentally friendly approach. Using as hole conductor the so-obtained PEDOT from PEP of bis-EDOT in aqueous electrolyte, the devices exhibited impressive power conversion efficiency of 5.2%. To compare the properties of the generated polymer from bis-EDOT in these two PEP methods, electron lifetime, photoinduced absorption (PIA) spectra, and UV–vis–NIR spectra were measured. The results showed that PEDOT from organic PEP exhibits a delocalized conformation with high conductivity and a smooth and compact morphology; a rough morphology with high porosity and polymer structure of relatively shorter chains was assumed to be obtained from aqueous PEP. Therefore, better dye regeneration but faster charge recombination was observed in the device based on PEDOT from aqueous PEP of bis-EDOT. Subsequently, to extend the aqueous PEP approach in consideration of the ability to decrease the oxidation potential of the precursor, the easily available precursor EDOT was for the first time used for PEP in aqueous medium in a variant of the aforementioned procedure, and the device based on the so-obtained PEDOT shows a more than 70-fold increase in efficiency, 3.0%, over that based on the polymer generated from EDOT by PEP in organic media. It was demonstrated that aqueous micellar PEP with EDOT as monomer is an efficient strategy for generation of conducting polymer hole-transporting materials.

Iod als neues Element wurde im Zusammenhang mit den Napoleonischen Kriegen 1811 entdeckt. Zum Anlass dieses zweihundertjährigen Jubiläums möchten wir auf die Geschichte der Erforschung und Nutzung dieses Elements zurückblicken und die vielen Facetten der Iodforschung beleuchten, die sich seit der Entdeckung herausgebildet haben. Iod beeinflusst viele Aspekte des Lebens auf der Erde und der menschlichen Zivilisation. Es wird in hohen Konzentrationen von marinen Algen akkumuliert, die die Ursache für einen bedeutenden Eintrag von Iod in die Küstenatmosphäre sind und dabei klimatische Prozesse beeinflussen. In marinen Sedimenten wird Iod als biophiles Element angesehen. Iod ist entscheidend für die Schilddrüsenfunktion von Wirbeltieren und damit von großer Bedeutung für die menschliche Gesundheit. Iod kommt in einer großen Zahl von Oxidationszuständen vor und zeichnet sich durch eine vielfältige supramolekulare Chemie aus. Iod ist einer Reihe analytischer Techniken zugänglich, und Iodverbindungen werden vielfach in organischen Synthesen eingesetzt. Elementares Iod wird in industriellen Größenordnungen produziert und findet ein breites Spektrum industrieller Anwendungen, insbesondere bei innovativen Werkstoffen wie Halbleitern – besonders auch in Solarzellen.

Iodine was discovered as a novel element in 1811 during the Napoleonic Wars. To celebrate the bicentennial anniversary of this event we reflect on the history and highlight the many facets of iodine research that have evolved since its discovery. Iodine has an impact on many aspects of life on Earth as well as on human civilization. It is accumulated in high concentrations by marine algae, which are the origin of strong iodine fluxes into the coastal atmosphere which influence climatic processes, and dissolved iodine is considered a biophilic element in marine sediments. Iodine is central to thyroid function in vertebrates, with paramount implications for human health. Iodine can exist in a wide range of oxidation states and it features a diverse supramolecular chemistry. Iodine is amenable to several analytical techniques, and iodine compounds have found widespread use in organic synthesis. Elemental iodine is produced on an industrial scale and has found a wide range of applications in innovative materials, including semiconductors—in particular, in solar cells.

[K+(2,2,2‐crypt)]2Ge92–containing the deltahedral Zintl anion Ge92–has been isolated from a solution of K4Ge9in ethylenediamine in the presence of 2,2,2‐crypt, intended as an intermediate in mixed‐cluster synthesis. The subsequent crystallographic characterisation shows the closo‐Ge92–cluster unit to be tricapped trigonal‐prismatic with a symmetry very close to D3h. Each Ge92–unit is surrounded by two 2,2,2‐crypt units, each with a chelated K+cation, viz. [K+(2,2,2‐crypt)]. The structure characterisation of this ordered Ge92–cluster is surprisingly enough the first one reported. A chemical bonding analysis reveals two local minima of D3hsymmetry, with that of lowest energy being highly similar to that resulting from the crystallographic analysis of low‐temperature data. The cluster interaction scheme is based on highly delocalised bonding.

The effects of additives guanidinium thiocyanate (GSCN) and N-methylbenzimidazole (MBI) on the photovoltaic performance of dye-sensitized solar cells based on low-viscous, binary ionic liquid and organic liquid electrolytes were investigated. Addition of only GSCN to the electrolyte has a pronounced influence on the short-circuit current, owing largely to the positive shift of the conduction band edge potential, probably increasing the injection efficiency of the excited dye. When only MBI was added to the electrolyte, a significant improvement of the open-circuit voltage was found, which could be attributed to a negative shift of the TiO2conduction band edge potential and a longer electron lifetime under open-circuit conditions. Synergistic effects were observed when GSCN and MBI were used together in the ionic liquid-based electrolyte. In this case, optimal open-circuit voltage and total conversion efficiency were obtained among the ionic liquid electrolytes studied mainly due to the more efficient retardation of the recombination loss reaction at the TiO2/electrolyte interface.

Deiodized salt: An organic redox couple (McMT−/BMT) was adopted for application in dye‐sensitized solar cells. Based on a low‐cost organic dye, TH305, an efficiency of 4.0 % was achieved under simulated sunlight (100 mW cm−2). Photoelectrochemical measurements provided insights into the difference between the organic redox couple and traditional iodine‐based electrolytes.

The present work describes the effects of different iodine concentrations and iodine-to-iodide ratios in electrolytes for dye-sensitized solar cells based on low-viscous, binary ionic liquid and organic liquid solvents. Current−voltage characteristics, photoelectrochemical measurements, electrochemical impedance spectroscopy, and Raman spectroscopy were used for characterization. Optimal short-circuit current and overall conversion efficiency were achieved using intermediate and low iodine concentration in ionic liquid-based and acetonitrile-based electrolytes, respectively. Results from photoelectrochemical and Raman-spectroscopic measurements reveal that both triiodide mobility and chemical availability affect the optimal iodine concentration required in these two types of electrolytes. The higher iodine concentrations required for the ionic liquid-based electrolytes partly compensate for these effects, although negative effects from higher recombination losses and light absorption of iodine-containing species start to become significant.

. The metal‐rich compounds [PdBi6][(Bi,Sn)1–δBr5–δ’] with δ1= 2/13, δ’1= 5/26, or δ2= δ’2= 2/12were synthesized from Bi2Pd, BiBr3, and Sn at 300 °C. The crystal structures contain intermetallic rods {}^1_\infty[Pd@Bi2/1Bi8/2]2.5+embedded in salt‐like matrices, which consist of groups of bromido‐bismuthate(III)‐stannate(II) octahedra [(Bi,Sn)nBr4n+2]m–(n= 2, 3) and isolated Br–ions. Metrical incompatibilities of the two subsystems in the crystalline metal‐salt hybrid result in non‐stoichiometry of the salt part associated with complex superstructures. The average structure is described in the orthorhombic space group Pmmmwith a≈︁ 408 pm, b≈︁ 2263 pm, c≈︁ 849 pm. It feigns statistical distribution of vacancies and orientational disorder of the concatenated octahedra. By choosing the modulation vectorsqi= 2/ta*+ ${1 \over 2}$b*+ ${1 \over 2}$c*with t1= 13 or t2= 12, the additional weak reflections of the diffraction patterns are indexed. Ordered structure models are achieved in the [3+1]‐dimensional superspace group Pmmm(α${1 \over 2}$${1 \over 2}$)000. Metallic conductivity along [100], i. e. the direction of the {}^1_\infty[Pd@Bi2/1Bi8/2]2.5+rods, was determined for a single‐crystal. One‐dimensional band structure calculations reveal Bi p‐bands crossing the Fermi level for formula charges higher than 2+. The electron localization indicator (ELI) indicates two‐center Bi–Bi bonds as well as multi‐center bonds inside the metallic part, whereas the bismuth lone‐pairs point towards the non‐conducting part of the structure.

The metal‐rich halogenides AuBi14–δSn2+δX21–δ(δ≈ 0.4) and PdBi15–δSn1+δX21–δ(δ≈ 0.6) with X= Cl, Br were crystallized from melts of the metals and BiX3. In the rhombohedral structures (space group R$\bar{3}$; a≈ 1050 pm; α≈ 94°), noble‐metal centered pentagonal antiprisms [Au@Bi10]5+resp. [Pd@Bi10]4+are embedded in halogenidometallate frameworks ∞3[Bi4–δSn2+δX21–δ]5–resp. ∞3[Bi5–δSn1+δX21–δ]4–. Mixed BiIII/SnIIsite occupation allows the framework to adopt different charges. Further exchange of BiIIIX3against SnIIX2results in vacancies (δ) on the position of an isolated halide ion. In quantum chemical calculations the naked metal‐clusters are found to be stable in D5dsymmetry with interatomic distances close to the observed ones. The significance of interactions between the Wade‐type host cluster Bi104+and the closed‐subshell guest atoms Au+or Pd0is reflected in the molecular orbital diagram, the population analyses and the ELI‐D.

Photosynthetic water oxidation is catalyzed by a manganese–calcium oxide cluster, which experiences five “S-states” during a light-driven reaction cycle. The unique “distorted chair”-like geometry of the Mn4CaO5(6)cluster shows structural flexibility that has been frequently proposed to involve “open” and “closed”-cubane forms from the S1to S3states. The isomers are interconvertible in the S1and S2states, while in the S3state, the open-cubane structure is observed to dominate inThermosynechococcus elongatus(cyanobacteria) samples. In this work, using density functional theory calculations, we go beyond the S3+Yzstate to the S3nYz•→ S4+Yzstep, and report for the first time that the reversible isomerism, which is suppressed in the S3+Yzstate, is fully recovered in the ensuing S3nYz•state due to the proton release from a manganese-bound water ligand. The altered coordination strength of the manganese–ligand facilitates formation of the closed-cubane form, in a dynamic equilibrium with the open-cubane form. This tautomerism immediately preceding dioxygen formation may constitute the rate limiting step for O2formation, and exert a significant influence on the water oxidation mechanism in photosystem II.

Specific interactions of the I−/I3−redox mediators with the reduced and oxidized dye, Ru(4,4′-dicarboxy-2,2′-bipyridyl)2(NCS)2, referred to as N3 or Ru(dcbpy)2(NCS)2, have been studied by means of density functional theory (DFT) with the focus on the charge transfer process involving {dye+I−} adducts; computations had been performed with a series of density functionals (gradient-corrected density functional BP86, and the hybrid density functionals B3LYP, MPW1K, B3PW1K, and MPW1PW91). Different pathways leading to {dye+I−} adducts have been studied. First, mechanistic insights into the interaction of I−with RuIII(dcbpy)2(NCS)2via an SCN−ligand directly giving rise to RuII(dcbpy)2(NCS)2I⌉0have been obtained with the distinctive S−I bonding. Second, the binding of I−to the N3 dye cation via I−−dcbpy interactions has been analyzed. We also report experimental and computational evidence that sheds light on the interaction of the redox mediator with bipyridyl moieties. Evidence for a charge transfer process in the presence of only one I−anion in the outer coordination sphere of the ruthenium center has been identified. Finally, geometries and electronic structures of plausible intermediates have been computationally analyzed based on an inner-sphere interaction between the metal center and the redox mediator, including a two-step regeneration reaction: RuIII(dcbpy)2(NCS)2⌉++ I−→ RuIII(dcbpy)2(NCS)I⌉++ SCN−, followed by the interaction of a second I−with the intermediate RuIII(dcbpy)2(NCS)I⌉+complex. Conclusive evidence of a charge-transfer process that gives rise to the regenerated RuIIcomplex, where I−interacts with the intermediate RuIII(dcbpy)2(NCS)I⌉+complex has been identified.

GalliumIII halides react with ceriumIII, ytterbiumIII, or dysprosiumIII halides in the presence of alkylated benzenes yielding mononuclear complexes of the general formula [Lnη6areneGaX43]. The Xray structures of [CeC6H5MeGaCl43] 1, [CepC6H4Me2GaCl43]·0.5pC6H4Me22, [YbC6H5MeGaCl43] 3, [YbpC6H4Me2GaCl43]·0.5pC6H4Me24, and [DyC6H5MeGaBr43] 5 were determined. Arene ligands in the cerium–toluene compound 1can be substituted by polycyclic aromatic hydrocarbons PAHs; the compounds [CenaphthaleneGaCl43] 6 and [CepyreneGaCl43]·0.5pyrene 7 have been isolated and structurally characterized. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008

A new bismuth subiodide Bi16I4was synthesized by hightemperature synthesis. Its structure was determined by singlecrystal Xray diffraction analysis [C2mNo. 12, a= 25.9486 Å, b= 4.3541 Å, c= 13.2593 Å, β= 104.482°, Z= 2, R1= 0.041, wRallF2 = 0.109]. The compound belongs to the BimI4m= 14, 16, 18 family of lowdimensional subhalides that feature onedimensional bismuth stripes of varying width, terminated by iodine atoms. Ab initio calculations at the DFT level were performed on 3D structures of all three BimI4compounds of the family. According to the computational data all three compounds are expected to exhibit metallic behavior and Pauli paramagnetism, with a directional anisotropy of the properties indicated by the calculated band structures. The molecular packing in bismuth subiodides has been analyzed in detail and two homologous series – Bi8+4nI4and Bi10+4nI4n= 0, 1, 2, ... – are suggested to describe existing and possible structures of the compounds of the BimI4family. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008

No Abstract

Five ionic liquids (ILs) of the general formula ImA-, where Im1-methyl-3-n-butyl-imidazolium, A-I-(1), BF4-(2), SCN-(3), CF3CO2-(4), and CF3SO3-(5), were used in electrolytes for dye-sensitized monolithic solar cells. The properties of the electrolytes and various characteristics of the solar cell performance, such as electron transport and electron lifetime, were studied. The composition of the binary electrolytes, i.e., the different anions, have a significant effect on the viscosity, but only a modest effect of the measured diffusion coefficient for triiodide. No significant effect of the electrolyte composition on the electron transport time in the mesoporous TiO2film was found, while there was a pronounced effect on the electron lifetime. Monolithic solar cells with thiocyanate, IL 3,showed overall light-to-electricity conversion efficiency up to 5.6% in 250 W m-2simulated sunlight and have promising stability.

The in vitro formation of carbonate apatite in solutions with ion concentrations comparable to those in human serum was studied. The composition and morphology of the resulting apatite precipitate displayed a hierarchical assembly of elongated plate-shaped nanocrystals of carbonate apatite analogous to previously characterized bioapatites formed in vivo. The main conclusion is that so-called bioapatites may form in vitro and that precipitation inhibitors most likely are essential for the prevention of spontaneous calcification at normal human serum ion concentrations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The reactions of platinum(II) iodide with triethyl‐ or trimethylsulfonium iodide in acetonitrile solution lead to the formation of crystalline products (Et3S)2[PtI6] (1) and [Me3S]2[PtI6]·CH3CN (2), respectively. The formation of Pt(IV) complexes may be explained either by disproportionation of PtI2or oxidation by oxygen. Palladium(II) iodide reacts with triethylsulfonium iodide to give the palladium(II) complex (Et3S)2[PdI4] (3). The crystal structures of 1–3were determined by single‐crystal X‐ray diffraction. In the crystal structures, the compounds 2and 3exhibit an extensive hydrogen‐bonding network.

The prospects of synthesizing polycationic species using GaBr3 in benzene solution at room temperature have been investigated. The salts Bi8[GaBr4]2, Sb8[GaBr4]2 and Te4[Ga2Br7]2 have been isolated and characterized. The first two compounds are isotypic with Sb8[GaCl4]2, crystallize in the space group Pna21, and feature square anti-prismatic E82+ polycations (E = Sb, Bi). Unit-cell parameters for Bi8[GaBr4]2 are a = 18.3014(10) Å, b = 10.3391(6) Å and c = 13.5763(7) Å, and for Sb8[GaBr4]2; a = 18.096(2) Å, b = 10.1572(9) Å and c = 13.2168(10) Å. Te4[Ga2Br7]2 crystallizes in the space group P21/c with a = 10.1600(9) Å, b = 10.8314(9) Å, c = 13.8922(10) Å and β = 99.182(7)°, and features a square-planar Te42+ polycation. The compound Bi5[GaBr4]3 has been synthesized from molten GaBr3 and characterized by using powder diffractometry in space group Fm-3c; a = 17.6263(8) Å. The structure model for this compound suggests the included Bi53+ cations to be practically freely oriented within its cavities in the solid phase. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The nonastannide clusters have been investigated usingEXAFS, NMR and Raman spectroscopy as well as quantum chemical calculations explicitly considering a model cationic field and solid-state statistics. NMR spectroscopic andEXAFS results are basically identical to those previously published and consistent with a fluctional model of the cluster. The quantum chemical calculations show that there is no significant difference in energy between the two model geometries, C4v and D3h, and that the vibrational frequencies are very low, clearly indicating that the cluster is expected to be fluctional. The solid-state statistics show that both model geometries can be used to describe all known nonastannide structures with reasonable success, illustrating that the classification of the nonastannide clusters in terms of specific symmetries is entirely arbitrary. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)