Colloidal particles with prescribed valency such as the tetrahedral patchy particles have long been seen as a viable route to technologically relevant open lattice structures on the scale of hundreds of nanometers. However, conceptual limitations and resulting competing local bonding configurations often lead to mixed lattice phases. Here, we present a DNA-origami enabled approach to controlling the attachment of tetrapod building blocks in predictable ways. By varying the relative strength of two designed binding configurations we are able to direct the assembly of tetrapod particles into diamond cubic, twinned diamonds, stacking-disordered mixtures, hexagonal diamonds, and sII clathrates. Under specific conditions, the diamond structures are interpenetrated by additional networks, resulting in triple cubic and triple hexagonal diamond structures. The 440 nm large unit cell of the clathrates shifts structural reflections into the visible range, giving these rationally designed, self-assembled crystals structural color.

This work investigates the growth mechanisms and optimization of optical properties in block copolymer (BCP)‐templated MAPbBr3 perovskite nanocrystals (PeNCs). Neutron scattering, transmission electron microscopy, and in situ optical spectroscopy studies combined with confinement‐model‐based size estimation of the nanocrystals during the perovskite formation revealed a complex multispecies growth behavior of BCP‐templated PeNCs, which was significantly influenced and could be controlled by systematically varying the stoichiometry between polystyrene‐b‐poly(2‐vinylpyridine) (PS‐b‐P2VP) and PbBr2 in the precursor, and the manner of adding the A‐cation either as a dispersion in a polymer solution or dissolved in methanol. The combination of optimized precursor stoichiometry and methanol‐based A‐cation addition yielded narrow emission linewidths of 83 meV and photoluminescence quantum yields of up to 87%. These findings provide new mechanistic insights and practical levers for improving BCP‐templated perovskite nanocrystals, paving the way for their application in future optoelectronic devices.

I-III-VI quantum dots are potential candidates for light-emitting and light-harvesting applications due to their heavy-metal–free composition and chemical tunability. Despite their potential, the investigation of intrinsic exciton and excitonic many-body dynamics has often been complicated because of their extensive defect energy landscape. Here, we investigate bright band-gap-emitting AgInS 2 quantum dots of sizes ranging from ∼ 4 to 7 nm using femtosecond pump-probe spectroscopy to link quantum confinement to exciton formation and many-body interactions. The exciton formation time is governed by inter-valence-band hole relaxation. This increases by more than a factor of 4 with decreasing quantum dot size, reflecting size-dependent exciton-phonon scattering efficiency. By temporally correlating hole relaxation with induced absorption dynamics, we identify different exciton-to-biexciton transitions originating from different exciton states. Excitation-fluence-dependent measurements reveal a biexciton decay time that scales with the quantum dot volume. Smaller quantum dots show fast decay of <100 ps, primarily governed by exciton-exciton annihilation. In larger quantum dots, the biexciton lifetime exceeds 400 ps, indicating reduced annihilation efficiency. Complementary streak-camera photoluminescence experiments provide direct spectroscopic evidence that these long-lived biexcitons are partially emissive. Collectively, we report an in-depth ultrafast-optical study yielding fundamental insights into the complex landscape of exciton formation and biexciton physics, which advances the understanding of intrinsic optical processes in AgInS 2 quantum dots among I-III-VI materials.

Lead halide perovskite nanocrystals (PNCs) exhibit outstanding optical and electronic properties for next-generation optoelectronics; however, their instability under ambient conditions severely hinders their practical implementation. Here, we demonstrate a versatile ligand cross-linking approach via electron-beam irradiation that effectively enhances nanocrystal stability without compromising their exceptional optical properties. Electron-beam exposure induces cross-linking reactions within the native oleylamine and oleic acid ligand shell, forming a robust, interconnected organic network that substantially increases hydrophobicity, long-term ambient stability, and resistance to various solvents. Unlike polymer or micelle encapsulation strategies, our cross-linking method preserves the structural integrity of the PNC layer and its optical properties without introducing additional layers or barriers that could impede charge transport. We further exploit this technique to create unprecedented heterostructures, achieving dual-emission spectra without ion exchange. Additionally, we present a novel method for producing mechanically stable, freestanding PNC films, which significantly simplifies device fabrication. These findings open up new avenues for integrating highly stable perovskite nanocrystal layers into commercial-scale photovoltaic and optoelectronic devices.

ABSTRACT Colloidal quantum dots (QDs) are promising for light‐emitting applications, but their synthesis under ambient conditions remains challenging. Here we present a rapid, room‐temperature (RT) method that produces highly stable QDs within minutes using the zwitterionic ligand 2‐ammonioethyl 2‐octyl‐1‐dodecyl phosphate (OD‐PEA). The strong binding of OD‐PEA enables precise size control and effective passivation, yielding blue‐emitting QDs () with narrow linewidths () and high photoluminescence quantum yields (up to 86 %). The QDs retain their optical quality for months in air and offer tunable emission from blue–cyan through ligand concentration, and from ultraviolet to deep red via halide exchange. A proof‐of‐concept perovskite light‐emitting diode (PeLED) fabricated from these QDs exhibits appreciable electroluminescence (EL) at with a low turn‐on voltage. This work establishes a simple and scalable strategy for producing stable, strongly confined perovskite QDs, advancing their potential for next‐generation optoelectronic and photonic technologies.

Perovskite nanocrystals have positioned themselves at the forefront for next-generation emitter applications due to their extraordinary optoelectronic properties, which include widely tunable narrow emission spectra and low-cost syntheses. However, stability issues and halide ion exchange inhibit the realization of heterostructures, severely limiting their applicability and decelerating their commercialization. Here, we combine a block copolymer templated halide perovskite nanocrystal synthesis with a post-synthetic treatment with UV-C light to obtain ultra-stable thin film emitters. The UV light induces cross-linking between the polymer strands, thereby rendering them insoluble to the organic solvent and nearly impervious to halide ion diffusion while retaining the nanocrystals’ optical properties. This method enabled the fabrication of an all-perovskite nanocrystal white light-emitting thin film. The resulting films feature narrow linewidths (< 95meV) for each RGB emission peak. Additionally, the color temperature of the ’white’ light can be tuned with a color gamut approximating the Rec. 2020 standard. These RGB-emissive phosphor films could be combined with commercial UV or blue LED backlights to create the next-generation high-efficiency, high-quality phosphor-converted white LEDs or color displays.

Lead halide perovskites combine outstanding optoelectronic performance with low‐cost and scalable manufacturing routes. However, their commercial success remains limited by a still‐evolving understanding of crystallization dynamics, a lack of sustainable, material‐informed processing techniques, and persistent challenges in fabricating blue‐emitting and 2D compositions with sterically‐impeded cations. Here, the interaction of light with organic–inorganic perovskite precursor solutions is uncovered by presenting a photochemically‐assisted crystallization control technique (PACCT). This low‐energy method leverages UV illumination to modulate reaction kinetics, allowing controlled crystal formation in both thin films and flexible perovskite‐polymer composites under ambient atmosphere at room temperature. The treatment's influence on the crystallization process either impedes (3D perovskites) or promotes (2D perovskites) crystal growth. In the latter case, this facilitates the growth of perovskites that can otherwise be challenging using thermal approaches, enabling a facile pathway toward blue emission and thin films with a photoluminescence stability exceeding 1000 h at 80 % relative humidity. For both reaction pathways, mechanistic descriptions are identified based on the UV‐induced deprotonation of the organic cation. Together, these results introduce a novel strategy for perovskite fabrication and provide new insights into their crystallization dynamics, offering a versatile and scalable route for advancing next‐generation optoelectronic materials with a reduced energy footprint.

I‐III‐VI quantum dots are eco‐friendly alternatives for next‐generation light‐emitting and harvesting devices. The study investigates the optical properties of Ag‐In‐S‐based quantum dots, focusing on excitonic transitions and sub‐bandgap defects. Uniquely synthesized AgInS 2 quantum dots emit via free excitons but dominate with broad, red‐shifted emission from energy‐distributed donor–acceptor pair defects. Photoluminescence excitation spectroscopy unveils charge carrier relaxation pathways with varying efficiencies within the defect states. Gallium sulfide coating forms a core/shell structure, passivating defects and transforming the inhomogeneous sub‐bandgap energy landscape into a more homogeneous one. A narrow free exciton emission and sharp absorption onset with two exciton signatures, X1 and X2, become prominent. Theoretical calculations reveal the band structure, showing that these transitions result from the excitation between two distinct valence band maxima and the conduction band minimum. Femtosecond transient transmission spectroscopy shows a defect trapping time of 590 fs in core quantum dots, while exciton filling prevails in core/shell, with formation times of 560 fs (X1) and 320 fs (X2). This study provides new insights into the optical properties of Ag‐In‐S‐based quantum dots by demonstrating how the computed band structure explains the experimentally observed excitonic features, with ultrafast spectroscopy capturing the exciton formation and trap‐state filling dynamics.

Precise and reproducible control over nanocrystal synthesis is essential for tailoring optical properties, yet remains a long‐standing challenge in halide perovskites. A broadly adoptable machine learning–guided framework, the Synthesizer, is introduced that combines Gaussian Process regression and Bayesian optimization with chemistry‐aware molecular encodings and systematic feature engineering. Rather than new algorithms, the advance lies in translating interpretable machine learning tools into a practical, benchtop platform for nanocrystal optimization under ambient conditions. Using CsPbBr 3 as a model system, nm‐level precision in photoluminescence peak tuning (430 nm to 520 nm) is achieved, along with benchmark narrow linewidths down to 70 meV via lateral confinement control, and robust photoluminescence quantum yield optimization linked to surface trap density. Mapping the two‐dimensional parameter space (Cs/PbBr 2 and antisolvent/PbBr 2 ratios) across multiple antisolvents enables predictive optimization and identifies the antisolvent/PbBr 2 ratio as a previously underappreciated mechanistic parameter, offering a quantitative basis for antisolvent‐accelerated nanocrystal growth. Transfer tests across distinct chemical spaces, including alcohols and cyclopentanone, confirm generalizability to unseen molecules, while application to CsPbI 3 demonstrates extension to new material systems. These results establish an adoption‐ready platform for data‐efficient, uncertainty‐aware synthesis design, providing reproducible pathways to accelerate materials discovery beyond halide perovskites.

Perovskite nanocrystals have positioned themselves at the forefront of next‐generation emitter applications due to their extraordinary optoelectronic properties, which include widely tunable narrow emission spectra and low‐cost syntheses. However, stability issues and halide ion exchange inhibit the realization of heterostructures, severely limiting their applicability and decelerating their commercialization. Here, a block copolymer templated halide perovskite nanocrystal synthesis with a post‐synthetic treatment is combined with UV‐C light to obtain ultra‐stable thin film emitters. The UV light induces cross‐linking between the polymer strands, thereby rendering them insoluble to the organic solvent and nearly impervious to halide ion diffusion while retaining the nanocrystals’ optical properties. This method enabled the fabrication of an all‐perovskite nanocrystal white light‐emitting thin film. The resulting films feature narrow linewidths ( < 95 meV) for each RGB emission peak. Additionally, the color temperature of the ’white’ light can be tuned with a color gamut approximating the Rec. 2020 standard. These RGB‐emissive phosphor films can be combined with commercial UV or blue LED backlights to create the next‐generation high‐efficiency, high‐quality phosphor‐converted white LEDs or color displays.

Lead halide perovskite nanocrystals (NCs) with narrow, bright emission in the visible range are promising candidates for light-emitting applications. Near-unity quantum yields have been realized for green and red-emitting perovskites, but efficient, stable blue-emitting perovskite materials are scarce. Current methods to synthesize quantum-confined CsPbBr3 NCs with blue emission are limited to specific wavelength ranges and still suffer from inhomogeneously broadened emission profiles. Herein, anisotropic blue-green emitting CsPbBr3 NCs are synthesized in ambient atmosphere using a spontaneous crystallization method. Optical spectroscopy reveals a gradual, asymptotic photoluminescence (PL) redshift of pristine colloidal NCs after synthesis. During this process, the emission quality improves notably as the PL spectra become narrower and more symmetric, accompanied by a PL intensity increase. Electron microscopy indicates that the gradual redshift stems from an isotropic growth of the CsPbBr3 NCs in at least two dimensions, likely due to residual precursor ions in the dispersion. Most importantly, the growth process can be halted at any point by injecting an enhancement solution containing PbBr2 and organic capping ligands. Thus, excellent control over NC size is achieved, allowing for nanometer-precise tunability of the respective emission wavelength in the range between 475 and 500 nm, enhancing the functionality of these already impressive NCs.

Achieving the goal of generating all of the world's energy via renewable sources and significantly reducing the energy usage will require the development of novel, abundant, nontoxic energy conversion materials. Here, a cost-efficient and scalable continuous flow synthesis of Cs3Cu2I5 nanocrystals is developed as a basis for the rapid advancement of novel nanomaterials. Ideal precursor solutions are obtained through a novel batch synthesis, whose product served as a benchmark for the subsequent flow synthesis. Realizing this setup enabled a reproducible fabrication of Cs3Cu2I5 nanocrystals. The effect of volumetric flow rate and temperature on the final product's morphology and optical properties are determined, obtaining 21% quantum yield with the optimal configuration. Consequently, the size and morphology of the nanocrystals can be tuned with far more precision and in a much broader range than previously achievable. The flow setup is readily applicable to other relevant nanomaterials. It should enable a rapid determination of a material's potential and subsequently optimize its desired properties for renewable energy generation or efficient optoelectronics.

While the role of crystal facets is well known in traditional heterogeneous catalysis, this effect has not yet been thoroughly studied in plasmon-assisted catalysis, where attention has primarily focused on plasmon-derived mechanisms. Here, we investigate plasmon-assisted electrocatalytic CO2 reduction using different shapes of plasmonic Au nanoparticles - nanocube (NC), rhombic dodecahedron (RD), and octahedron (OC) - exposing {100}, {110}, and {111} facets, respectively. Upon plasmon excitation, Au OCs doubled CO Faradaic efficiency (FECO) and tripled CO partial current density (jCO) compared to a dark condition, with NCs also improving under illumination. In contrast, Au RDs maintained consistent performance irrespective of light exposure, suggesting minimal influence of light on the reaction. Temperature experiments ruled out heat as the main factor to explain such differences. Atomistic simulations and electromagnetic modeling revealed higher hot carrier abundance and electric field enhancement on Au OCs and NCs than RDs. These effects now dominate the reaction landscape over the crystal facets, thus shifting the reaction sites when comparing dark and plasmon-activated processes. Plasmon-assisted H2 evolution reaction experiments also support these findings. The dominance of low-coordinated sites over facets in plasmonic catalysis suggests key insights for designing efficient photocatalysts for energy conversion and carbon neutralization. Crystal facets are known to be important in traditional heterogeneous catalysis, yet this effect has not been studied in plasmon-assisted catalysis. Here, the authors investigate the impact facets have on CO2 reduction using plasmonic Au NPs.

Colloidal lead halide perovskite nanocrystals hold enormous potential for lighting applications due to their outstanding optical properties. Precise control of the nanocrystal dimensions and composition is a prerequisite for establishing practical applications. However, the rapid nature of their synthesis precludes a detailed understanding of the synthetic pathways, thereby limiting the optimization. Here, we deduce the formation mechanisms of anisotropic lead halide perovskite nanocrystals, 1D nanorods and 2D nanoplatelets, by combining in situ X-ray scattering and photoluminescence spectroscopy. In both cases, emissive prolate nanoclusters form upon mixing of the two precursor solutions. The divergent anisotropy is induced by ensuing antisolvent addition: The intermediate nanoclusters are driven into a dense hexagonal mesophase, where they fuse to form nanorods. Contrastingly, nanoplatelets grow freely dispersed from dissolving nanoclusters, stacking subsequently in lamellar superstructures. Shape and size control of the nanocrystals are determined primarily by the antisolvent's dipole moment and Hansen hydrogen bonding parameter. Exploiting the interplay of antisolvent and organic ligands could enable more complex nanocrystal geometries in the future.

Nanocrystal self-assembly into supercrystals provides a versatile platform for creating novel materials and devices with tailored properties. While common self-assembly strategies imply the use of purified nanoparticles after synthesis, conversion of chemical precursors directly into nanocrystals and then supercrystals in simple procedures has been rarely reported. Here we study the nucleation and growth of CuPd icosahedra and their consecutive assembly into extended closed-packed face-centered cubic (fcc) supercrystals. To this end, we simultaneously and in situ measure X-ray total scattering with pair-distribution function analysis (TS-PDF) and small-angle X-ray scattering (SAXS). We find that the supercrystals formation is preceded by an intermediate dense phase of nanocrystals displaying short-range order (SRO). We further show that the organization of oleic acid/oleylamine surfactants into lamellar structures likely drives the emergence of the SRO phase and later of the supercrystals by creating an excluded volume to particle diffusion. The supercrystal formation as well as their disassembly are triggered by temperature. Our study demonstrates that depletion effects can be crucial in the direct synthesis of supercrystals. We also provide a general approach to investigate novel preparation routes of supercrystals in situ and across several length scales via X-ray scattering.

In photocatalysis, photogenerated charge separation is pivotal and can be achieved through various mechanisms. Building heterojunctions is a promising method to enhance charge separation, where effective contact and charge exchange between heterojunction components remains challenging. Mostly used synthesis processes for making heterostructures require high temperatures, difficult processes, or expensive materials. Herein, a heterojunction of potassium intercalated graphitic carbon nitride (K-CN) and nanoflakes of iron phosphor trisulfide (FPS) is designed via a simple mechanical grinding process to boost the hydrogen evolution by a factor of more than 25 compared to pure K-CN. This significant improvement is rarely reached by other combinations of two semiconductors without cocatalysts, such as platinum. It can be attributed to the band alignment and band bending of an S-scheme that is validated via optical and X-ray photoelectron spectroscopy. As a consequence, strong quenching of the photoluminescence and significant H2 evolution occur for this unique heterojunction. Furthermore, the excellent durability of the designed photocatalytic heterostructure is confirmed by monitoring the catalysts' H2-evolution rate and crystal structure after 72 h under light illumination. This study opens up promising and simple pathways for constructing efficient S-scheme heterojunctions for photocatalytic water-splitting.

Trap states of the semiconductor/gate dielectric interface give rise to a pronounced subthreshold behavior in field‐effect transistors (FETs) diminishing and masking intrinsic properties of 2D materials. To reduce the well‐known detrimental effect of SiO 2 surface traps, this work spin‐coated an ultrathin (≈5 nm) cyclic olefin copolymer (COC) layer onto the oxide and this hydrophobic layer acts as a surface passivator. The chemical resistance of COC allows to fabricate monolayer MoS 2 FETs on SiO 2 by standard cleanroom processes. This way, the interface trap density is lowered and stabilized almost fivefold, to around 5 × 10 11 cm −2 eV −1 , which enables low‐voltage FETs even on 300 nm thick SiO 2 . In addition to this superior electrical performance, the photoresponsivity of the MoS 2 devices on passivated oxide is also enhanced by four orders of magnitude compared to nonpassivated MoS 2 FETs. Under these conditions, negative photoconductivity and a photoresponsivity of 3 × 10 7 A W −1 is observed which is a new highest value for MoS 2 . These findings indicate that the ultrathin COC passivation of the gate dielectric enables to probe exciting properties of the atomically thin 2D semiconductor, rather than interface trap dominated effects.

Heterovalently substituting toxic lead is an increasingly popular design strategy to obtain environmentally sustainable variants of the exciting material class of halide perovskites. Perovskite nanocrystals (NCs) obtained through solution-based methods exhibit exceedingly high optical quality. Unfortunately, most of these synthesis routes still require reaction under inert gas and at very high temperatures. Herein a novel synthesis routine for lead-free double perovskite (LFDP) NCs is presented. An approach based upon the hot injection and ligand-assisted reprecipitation (LARP) methods to achieve a low-temperature and ambient atmosphere-based synthesis for manganese-doped Cs2 NaBiCl6 NCs is presented. Mn incorporation is critical for the otherwise non-emissive material, with a 9:1 Bi:Mn precursor ratio maximizing the bright orange photoluminescence (PL) and quantum yield (QY). Higher synthesis temperatures slightly increase the material's performance, yet NCs synthesized at room temperature are still emissive, highlighting the versatility of the synthetic approach. While the material's indirect bandgap limits its appeal for optoelectronics, this feature could benefit photocatalysis due to longer carrier lifetimes. Moreover, the developed synthesis is facile and can rapidly be adapted to other more viable material compositions and up-scaled to realize applications directly.

Perovskite Solar Cells In article 2208061, Lukas E. Lehner, Martin Kaltenbrunner, and co-workers report the controlled nucleation of quasi-2D perovskites at the liquid–air interface of the precursor solution. Restricting the initial crystal growth to the surface of the liquid results in highly aligned perovskite thin films with improved charge transport, enabling efficient solar cells with excellent stability.

CuBi2 O4 has recently emerged as a promising photocathode for photo-electrochemical (PEC) water splitting. However, its fast degradation under operation currently poses a limit to its application. Here, we report a novel method to study operando the semiconductor-electrolyte interface during PEC operation by surface-sensitive high-energy X-ray scattering. We find that a fast decrease in the generated photocurrents correlates directly with the formation of a metallic Bi phase. We further show that the slower formation of metallic Cu, as well as the dissolution of the electrode in contact with the electrolyte, further affect the CuBi2 O4 activity and morphology. Our study provides a comprehensive picture of the degradation mechanisms affecting CuBi2 O4 electrodes under operation and poses the methodological basis to investigate the photocorrosion processes affecting a wide range of PEC materials.