Organic-inorganic hybrid materials based on lead and bismuth have recently been proposed as novel X- and gamma-ray detectors for medical imaging, non-destructive testing, and security, due to their high atomic numbers and facile preparation compared to traditional materials like amorphous selenium and Cd(Zn)Te. However, challenges related to device operation, excessively high dark currents, and long-term stability have delayed commercialization. Here, two novel semiconductors incorporating stable sulfonium cations are presented, [(CH3CH2)3S]6Bi8I30 and [(CH3CH2)3S]AgBiI5, synthesized via solvent-free ball milling and fabricated into dense polycrystalline pellets using cold isostatic compression, two techniques that can easily be upscaled, for X-ray detection application. The fabricated detectors exhibit exceptional sensitivities (14 100-15 190 mu C Gyair-1 cm-2) and low detection limits (90 nGyair s-1 for [(CH3CH2)3S]6Bi8I30 and 78 nGyair s-1 for [(CH3CH2)3S]AgBiI5), far surpassing current commercial detectors. Notably, they maintain performance after 9 months of ambient storage. The findings highlight [(CH3CH2)3S]6Bi8I30 and [(CH3CH2)3S]AgBiI5 as scalable, cost-effective and highly stable alternatives to traditional semiconductor materials, offering great potential as X-ray detectors in medical and security applications.

Natural photosynthesis plays a vital role in the supply of energy and oxygen necessary for the survival of biological organisms. The current leading proposal of the O-O bond formation in photosystem II suggests the coupling between the central mu-oxo (O5) and the additional oxygenic ligand (Ox) of the manganese-calcium oxide cofactor. However, the subsequent process through which molecular dioxygen is formed and released remains elusive. In this report, quantum chemical calculations reveal that the O-2 release process is initiated by the cleavage of the Mn-O5 bond, without a preliminary conformational change of the peroxide [O5-Ox](2-) group. Subsequently, the [O5-Ox] moiety is converted from the superoxide to the weakly bound quasi-O-2 where the Mn-Ox bond is cleaved, and after a twist of the quasi-O-2 unit, the free O-2 is ultimately released. Alternative pathways display significantly slower kinetics, due to the lower structural stabilities of the rate-limiting transition states. The cause of the difference is associated with the Jahn-Teller axial orientation and the local ring strain within the Mn cluster. These findings contribute to unravelling the intricate mechanism involved in an important step of photosynthetic oxygen evolution for a deeper understanding of nature's water oxidation catalysis.

The Mn4CaO5(6) cluster in photosystem II catalyzes water splitting through the Si state cycle (i = 0–4). Molecular O2 is formed and the natural catalyst is reset during the final S3 → (S4) → S0 transition. Only recently experimental breakthroughs have emerged for this transition but without explicit information on the S0-state reconstitution, thus the progression after O2 release remains elusive. In this report, our molecular dynamics simulations combined with density functional calculations suggest a likely missing link for closing the cycle, i.e., restoring the first catalytic state. Specifically, the formation of closed-cubane intermediates with all hexa-coordinate Mn is observed, which would undergo proton release, water dissociation, and ligand transfer to produce the open-cubane structure of the S0 state. Thereby, we theoretically identify the previously unknown structural isomerism in the S0 state that acts as the origin of the proposed structural flexibility prevailing in the cycle, which may be functionally important for nature’s water oxidation catalysis.

Organic hole-transporting materials (HTMs) are of importance in the progress of new-generation photovoltaics, notably in perovskite solar cells (PSCs), solid-state dye-sensitized solar cells (sDSCs), and organic solar cells (OSCs). These materials play a vital role in hole collection and transportation, significantly impacting the power conversion efficiency (PCE) and overall stability of photovoltaic devices. The emergence of spiro(fluorene-9,9 '-xanthene) (SFX) as a novel building block for organic HTMs has gained considerable attention in the field of photovoltaics. Its facile one-pot synthetic approach, straightforward purification, and physiochemical properties over the prototype HTM spiro-OMeTAD have positioned SFX as a highly attractive alternative. In this Account, we present a comprehensive and in-depth summary of our research work, focusing on the advancements in SFX-based organic HTMs in photovoltaic devices with a particular emphasis on PSCs and sDSCs. Several key objectives of our research have been focused on exploring strategies to improve the properties of SFX-based HTMs. (i) One of the critical aspects we have addressed is the improvement of film quality. By carefully designing the molecular structure and employing suitable synthetic approaches, we have achieved HTMs with excellent film-forming ability, resulting in uniform and smooth films over large areas. This achievement is pivotal in ensuring the reproducibility and efficiency of photovoltaic devices. Furthermore, (ii) our investigations have led to an improvement in hole mobility within the HTMs. Through molecular engineering, such as increasing the molecular conjugation and introducing multiple SFX units, we have demonstrated enhanced charge-carrier mobility. This advancement plays a crucial role in minimizing charge recombination losses and improving the overall device efficiency. Additionally, (iii) we have explored the concept of defect passivation in SFX-based HTMs. By incorporating Lewis base structures, such as pyridine groups, we have successfully coordinated to Pb2+ in the perovskite layer, resulting in a passivation of surface defects. This defect passivation contributes to better stability and enhanced device performance. Throughout our review, we highlighted the potential and opportunities achieved through these steps. The combination of enhanced film quality, improved hole mobility, and defect passivation resulted in remarkable photovoltaic performance. Our findings have demonstrated promising short-circuit current densities, open-circuit voltages, fill factors, and PCEs, with some HTMs even outperforming the widely used spiro-OMeTAD. We believe that this review will not only provide a better understanding of SFX-based HTMs but also open new avenues for enhancing the performance of organic HTMs in photovoltaic and other organic electronic devices. By providing unique perspectives and exploring different strategies, we aim to inspire ongoing advancements in photovoltaic technologies and organic electronics. Meanwhile, the success of SFX-based HTMs in improving photovoltaic device performance holds great promise for the continued development of efficient and stable photovoltaic devices in the years to come.

Currently, there is a strong need to accelerate development of systematic and robotized procedures for discovery of photovoltaic materials in order to aid the transition toward the use of clean and sustainable energy sources. Perovskite-type materials represent a broad class of compounds that have recently attracted great interest for application as photovoltaic materials. Such materials offer a vast chemical and structural space, qualifying them as an interesting starting point for further exploration using robotized screening methods. In this work, the development and application of a robotized procedure for the screening and solar cell characterization of perovskite-inspired materials is presented. Several combinations of cationic dyes and metal halides were examined by using a fully automated robotic screening cycle, including solar cell characterization based on triple mesoscopic solar cell devices. It is shown that the presented methodology is promising for the detection of new photovoltaic materials, which is demonstrated by the discovery of a selection of photovoltaic candidates. Some of the discovered candidates, for instance [QR]-[PbI3], were further characterized theoretically and experimentally.

O2 formation 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” Mn4CaO6 cluster, which is supported experimentally by the S3 state of cyanobacterial PSII featuring an additional Mn-bound oxygenic ligand. However, it was recently proposed that the major structural form of the S3 state of higher plants lacks this extra ligand, and that the resulting S4 state would feature instead a penta-coordinate dangler Mn(V)=oxo, covalently linked to a “closed-cubane” Mn3CaO4 cluster. 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 S4 state through the sequential formation of peroxide and superoxide, followed by O2 release 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 O2 formation in natural photosynthesis, in particular for higher plants.

The present chapter offers an overview of polyanions of the Group 17 as examples of catenation. The main knowledge obtained from the rich literature on polyiodides is summarized, and comparisons are made with other polyhalide systems in order to gain insights into similarities and differences. A strong emerging field is represented by polybromides in the liquid and solid state, as well as novel or rejuvenated areas of application. A detailed analysis of chemical bonding is given, and the special properties of halogen-halogen bonding are highlighted.

In this work, we present the ionic liquid (IL) synthesis of two novel and [Et3S][AuI4][I-5] (2), and their application as active layers in monolithic solar cells. The compounds are composed of tetraiodoaurate anions and polyiodide entities, infinite polyiodide chains in 1 and pentaiodides in 2, which display short intermolecular contacts resulting in relatively small electronic bandgaps. This work represents the first demonstration of film deposition of gold iodide/polyiodide compounds onto porous monolithic substrates with subsequent solar cell characterization. The devices show promising photovoltaic performance and could unlock new materials design possibilities, ultimately moving away from lead-based photovoltaic materials. These findings further highlight the use of simple polyiodide entities to increase the structural and electronic dimensionality of gold perovskite-type anions.

A fast transition towards the use of clean and green energy sources requires accelerated discovery of new energy storage systems and devices. In this concept automation and robotics can play a key role. Here we present the development of a robotized platform, Poseidon, for the screening and discovery of new water-based electrolyte candidate systems for lithium-ion batteries (LIBs) systems. We have successfully demonstrated the Poseidon screening and characterisation capabilities for electrolytic discovery, which includes a range of steps such as electrolyte formulation, Raman spectroscopic characterization, coin-cell mounting/disassembling and electro-chemical battery evaluation via an accelerated screening cycling procedure. A comparison with analogous manual laboratory experiments shows that relevant accuracy for robotized screening purposes has been estab-lished. Furthermore, the presented accelerated charge/discharge cycling procedure is shown to be adequate for screening purposes of the test system.