Lars Kloo

Conventional semiconductor technologies rely on pure, highly ordered crystalline solids in which electronic coherence and minimal defect densities enable band-like charge transport. Liquids, in contrast, generally lack long-range structural order and conduct electricity (if at all) through ionic motion or hopping mechanisms. The development of liquid materials exhibiting semiconducting behavior could therefore offer substantial advantages, including compositional versatility, tolerance to defects and impurities, environmental stability, and compatibility with scalable deposition techniques. In this work, we demonstrate that elemental selenium can be incorporated into systems based on the organic superbase 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to form stable colloids of amorphous selenium nanoparticles at room temperature, as confirmed with a selection of characterization techniques. Electrochemical and optical experiments reveal reversible photoresponsive behavior and most likely mixed ionic-electronic transport. While illumination induces a pronounced decrease in impedance and an increase in current response, consistent with photogenerated charge carriers within the bulk selenium phase. Although the system remains structurally disordered and colloidal in nature, it poses several characteristics commonly associated with semiconducting materials. Consequently, these DBU-stabilized colloids present a promising, synthetically simple platform for liquid semiconducting media that could offer a pathway toward defect-tolerant soft materials. The results from this study form a foundation that can inspire an interest in a research area involving liquid semiconductors, soft electronics, adaptive materials, ionic-electronic coupling, and photodoped fluids.

The anchoring group of self‐assembled monolayer (SAM) hole‐transporting materials dictates both substrate binding and interfacial passivation, serving as a key lever for high‐performance perovskite photovoltaics. Herein, we report a novel SAM molecular material, denoted by XS21 , engineered with a multidentate dipicolinic acid (DPA) anchoring core to address conventional adhesion and degradation limitations. From an experimental perspective, the DPA anchor is found to promote molecular chemisorption onto the substrate, potentially originating from the dual‐action mechanism of pyridine–Ni coordination coupled with dicarboxylate‐metal interaction. Furthermore, XS21 imparts both low acid‐dissociation constants ( K _a ) and superior ultraviolet (UV) photostability. Consequently, wide‐bandgap (1.79 eV) perovskite solar cells containing XS21 deliver a champion power conversion efficiency (PCE) of 21.54% with an exceptional open‐circuit voltage of 1.372 V. Crucially, integrating XS21 into monolithic all‐perovskite tandem solar cells yields a remarkable PCE of 29.62%, alongside an outstanding operational stability (retaining >90% of initial efficiency after 900 h of continuous operation). This work establishes multi‐dentate pyridine‐carboxylate anchoring as a vital paradigm for next‐generation efficient and stable perovskite photovoltaics.

Metal oxide nanozymes are emerging as robust redox catalysts, yet the molecular basis of their substrate selectivity and reaction pathways remains poorly understood. Here, we identify 20 mol% Mn-doped TiO2 as a nanozyme platform that selectively oxidizes aromatic amino acids through a surface-confined pathway distinct from conventional diffusible radical-mediated oxidation. Using tyrosine, histidine, and phenylalanine together with 13C/15N isotopically labeled analogues, we combined high-resolution NMR spectroscopy, LC-MS/MS, X-ray photoelectron spectroscopy, and density functional theory calculations to resolve the underlying reaction mechanism. The data show that substrate oxidation proceeds through direct coordination to Mn-modified surface sites, followed by oxidative deamination, Cα–Cβ bond cleavage, and decarboxylation to yield the corresponding aldehydes: 4-hydroxybenzaldehyde, 1H-imidazole-4-carbaldehyde, and benzaldehyde. Isotopic labeling establishes that this transformation follows a Strecker-type degradation pathway localized at the nanozyme interface. XPS analysis demonstrates preservation of the Mn surface redox profile during catalysis, consistent with reversible Mn(III)/Mn(IV) cycling within the TiO2 lattice. Computational modeling further supports the thermodynamic feasibility of sequential proton-coupled electron-transfer steps leading to oxidative fragmentation. These findings establish that Mn doping programs TiO2 surfaces for selective dehydrogenase-like reactivity, through surface-directed interfacial oxidation, distinct from conventional diffusible radical-mediated pathways. The results provide a framework for rationally engineering metal oxide nanozymes with enzyme-like selectivity for targeted biomolecular transformations.

The investigation of dyes in perovskite solar cells (PSCs) is an emerging field, since dyes may introduce a range of effects beyond conventional light harvesting. However, the large number of possible materials and processing combinations make systematic investigation challenging. This study presents a hybrid and transferable strategy combining automated workflows and supporting manual evaluation to gain insights into the effects of dyes in PSCs. Using a near-infrared (NIR) dye and a typical lead halide perovskite, an automated synthesis-characterization workflow is demonstrated to be suitable for the evaluation of the effects of a dye either as a precursor additive or as a post-treatment material using photoluminescence as the key performance parameter. In addition, the automated synthesis-device fabrication-evaluation workflow can provide guidance for identifying a suitable concentration range of dye additives in precursor solutions. Computational results at density-functional theory (DFT) level and manually performed experiments suggest that the dye MK245 interacts with the perovskite and modifies its local or interfacial electronic environment. Integration of MK245 can significantly improve the device stability both in mesoscopic triple-layer perovskite solar cells and in conventional thin-film solar cells.

Two new star-shaped donor–acceptor oligomers, named TxBT and TxNT, with a truxene donor core and either 2,1,3-benzothiadiazole (BT) or a naphtho[1,2- c :5,6- c ′]bis[1,2,5]thiadiazole (NT) unit, respectively, have been developed for photocatalytic hydrogen production.

Photocatalysis offers a promising approach for renewable energy conversion and storage, but short lifetimes of charge-separated states in photocatalysts due to charge recombination limit its utility. Here we report an organic molecule with an acceptor–donor–acceptor configuration that can self assemble into highly crystalline nanoparticles. Transient absorption spectroscopy reveals that these crystalline assemblies can induce an ultra-long-lived charge-separated state of up to 1.2 s, attributed to initial symmetry-breaking charge separation, followed by charge hopping across closely packed molecules. These self-assembled nanoparticles have an impressive photocatalytic H ₂ evolution rate of 126 mmol g ⁻¹ h ⁻¹ with an external quantum efficiency of 12% at 550 nm under optimized conditions. This system shows a remarkable stability with 220 million turnover numbers (per particle) over the 77 h of operation. These findings suggest that rational design of organic molecules and their aggregates is vital for improving light-induced charge separation and for developing highly efficient, stable and scalable organic photocatalysts.

The urgent need for renewable energy solutions requires rapid advancements in materials discovery. In response, we present AURORA, an innovative robotic platform that enhances this process by integrating automated synthesis, characterization, and evaluation into a single unit, thereby improving efficiency and reducing errors. Its modular design allows for adaptable screening of diverse materials, including metal halide perovskites, and their application in solar cell devices. Our study demonstrates the ability of AURORA to autonomously synthesize and evaluate polycrystalline, mixed halide perovskites, including a novel mesoscopic solar cell array with improved data reliability and throughput. AURORA also conducts postsynthesis treatments and dynamic analyses under stress, setting it apart from traditional methods. These features make AURORA a transformative tool for the discovery of novel materials, with potential machine learning integration for optimization. Our results highlight the application of AURORA as a robust and adaptable platform for future developments in automated materials research.

The establishment of simple and efficient lead recycling pathways from lead–acid batteries for fabricating perovskite solar cells promotes the sustainable utilization of toxic lead compounds and advances the development of perovskite photovoltaics.

The Mn₄CaO₅₍₆₎ cluster in photosystem II catalyzes water splitting through the S_i 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.

Efficient photosensitizers are crucial for advancing solar energy conversion and storage technologies. In this study, we designed and synthesized a novel organic dye, denoted as YB6, for p‐type dye‐sensitized solar cells (p‐DSCs) and photoelectrochemical H₂O₂ production. YB6 features an extended conjugated π‐bridge derived from indacenodithieno[3,2‐b]thiophene and exhibits notable advantages: a two‐fold higher molar extinction coefficient at its main absorption peak and a broader absorption as compared to the PB6 dye. In p‐type dye‐sensitized NiO photoelectrochemical cells, the YB6‐based device demonstrated superior performance as compared to the PB6‐based device. It delivered nearly a 50 % higher H₂O₂ production over 5 hours. Furthermore, when fabricated into p‐DSCs, the YB6‐based device exhibited a 33 % higher power conversion efficiency. This enhancement is caused by suppressed charge recombination from the dye structure, which in turn may be traced to a larger thermodynamic up‐hill process for recombination losses in the YB6‐based system.