Halide perovskites possess an intrinsically dynamic structure that strongly influences their electro-optical performance and stability. Understanding how a microscopic phenomenon affects a global physical property is critical for better using these materials. Here, we suggest a new mechanism that explains synchronized electron-hole radiative recombination that extends over 10 & micro;m well beyond the current understanding. The physical observable we follow is photoluminescence intermittencies in vapor grown, all-inorganic halide perovskite crystals. This blinking effect is synchronized across distances well beyond the electron diffusion length, contradicting the widely accepted theory that assumes a "supertrap" involvement in photoluminescence intermittencies in halide perovskites. Such theories limit the range of synchronization of electron-hole radiative recombination by an order of magnitude to what we measure. We show beyond doubt a clear connection between the appearance of blinking and Pb-rich growth conditions. Thus, the new framework puts the focus on hole diffusion to explain micron scale synchronization in halide perovskites.

Two-dimensional (2D) organic-inorganic hybrid halide perovskites offer exceptional structural tunability and environmental stability arising from their layered architecture. However, their intrinsically anisotropic and poor thermal transport presents a critical bottleneck for device stability and operation. Here, we systematically investigate compositionally engineered thermal transport in a series of 2D perovskites through simultaneous variation of pi-conjugated, semiconducting organic-spacer cations and metal cations using a noninvasive vibrational pump-visible probe (VPVP) platform. Time-resolved VPVP spectroscopy and microscopy independently quantify cross-plane and in-plane thermal diffusivities and the evaluation of anisotropic heat flow. We found that incorporation of semiconducting organic spacer molecules enhances cross-plane thermal transport while suppressing in-plane heat conduction, progressively reducing thermal anisotropy and approaching near-isotropic heat transport for extended conjugated organic spacers. Metal cation substitution further modulates thermal transport, with Sn-based 2D perovskites exhibiting enhanced thermal diffusivity relative to Pb analogues, whereas Ge incorporation introduces increased lattice anharmonicity arising from asymmetric metal-halide bonding, leading to weakened heat propagation. Correlating thermal diffusivities with structural parameters, including interlayer spacing and octahedral distortion, reveals that phonon transport in 2D perovskites can be rationally tuned through organic-inorganic lattice design.

Transition-metal dichalcogenide (TMD) monolayers exhibit unique electronic, photonic, and quantum phenomena, yet their material quality remains constrained by defects and thickness inhomogeneity during chemical vapor deposition. Here, we identify the limitations of the common metal trioxide precursors: high volatility that induces stochastic vapor-phase nucleation and multilayer growth, and liberated oxygen-species-mediated chemical etchants that degrade lattice integrity. We demonstrate that an acid-mediated one-step modification, dissolving trioxides in hydrochloric acid, fundamentally redirects the precursor chemistry toward nonvolatile and substrate-anchored dioxide phase. This enforces a spatially confined solid-phase chalcogenization (SPC), minimizing the vapor-phase species and thereby suppressing dechalcogenization and vertical growth. The resulting uniform monolayers, synthesized as isolated triangular flakes or continuous films, achieve state-of-the-art low defect densities: 1.87 × 1012 cm-2 for MoS2 and 1.26 × 1012 cm-2 for WSe2. Our work establishes SPC as a simple and unified mechanistic framework to drive TMD synthesis toward the intrinsic structural limits.

Methanol, an important liquid fuel and chemical feedstock, has yet to be produced using solar energy, H2O, and CO2 as sole inputs in a standalone device. This study directly addresses this longstanding challenge through presenting the first demonstration of unbiased solar methanol production from CO2 and H2O with a monolithic artificial leaf design, surpassing the previous best energy efficiency in solar alcohol production by at least 1 order of magnitude. We first develop a new generation of photocathodes based on Si micropillar arrays and a cobalt tetraaminophthalocyanine molecular catalyst. By integrating a C60 interlayer that facilitates unidirectional electron transfer through the semiconductor/catalyst interface, we realize a photovoltage of 500 mV, one of the highest recorded for single-junction Si-based photoelectrodes in aqueous CO2 reduction, as well as unprecedented methanol formation with a Faradaic efficiency of 30% and a partial current density of 6.3 mA cm-2. We further integrate the photocathode with a multijunction perovskite photovoltaic minimodule to afford a standalone solar fuel system, which demonstrates a light-to-methanol conversion efficiency of 0.8%, 32 times higher than the present record in light-to-alcohol conversion with an artificial leaf.

Sunlight-driven photocatalytic oxidation, using ambient air as the oxidant, offers a sustainable route for removing chlorinated volatile organic compounds (VOCs) such as trichloroethylene (TCE). Yet, practical implementation is hindered by low reaction rates and undesirable product selectivity. Here, we present a material design strategy that overcomes both challenges. Size-controlled anatase TiO2 nanocrystals with truncated bipyramid (nanoTBP) morphology achieve exceptional photocatalytic activity for TCE degradation, comparable to rates reported for energy-intensive thermal catalysis, with unoptimized CO2/CO product ratios. Decorating as-synthesized TiO2 with Pt nanoparticles significantly enhances the CO2 selectivity but significantly diminishes the overall reaction rates. To resolve this rate-selectivity trade-off, we integrate Pt/TiO2 with pristine TiO2 into an optimized composite photocatalyst, unlocking a tandem pathway that enables both rapid degradation and complete mineralization of TCE to CO2 under solar irradiation. Taken together, this work establishes a scalable, solar-enabled, materials-based strategy for complete gas-phase mineralization of TCE, with broader implications for novel and sustainable VOC treatment processes.

Photothermal CO2 hydrogenation is a promising route to produce methanol as a sustainable liquid solar fuel. However, most existing catalysts require a combination of solar irradiation and additional heat input to achieve a satisfactory reaction rate. For the few that can be driven solely by light, their reaction rates are one order of magnitude lower. We develop a photothermal catalyst with multilevel interfaces that achieves improved methanol production from photothermal CO2 hydrogenation without external heat. The catalyst features a layered structure comprising Cu/ZnO/Al2O3 (CZA) covered by oxidized carbon black (oCB), where the oCB/CZA interface promotes efficient heat generation and transfer, and the Cu/oxide interface contributes to high catalytic activity. Under a mild pressure of 8 bar, our oCB/CZA catalyst shows a methanol selectivity of 64.7% with a superior production rate of 4.91 mmol·gcza−1·h−1, at least one order of magnitude higher than other photothermal catalysts solely driven by light. This work demonstrates a photothermal catalyst design strategy for liquid solar fuel production.

Decoding arbitrary polarization information in a cost-effective way is a key target for next-generation optical sensing. However, the design of full-Stokes detectors capable of resolving polarization states in a single shot remains challenging. Here we introduce GOStokes, an approach that leverages heterogeneous grain orientation in solution-processed metal halide semiconductors to extract Stokes parameters in a single measurement. By developing polycrystalline films exhibiting strong inherent circular and linear dichroism, we harness randomly oriented grains to produce varied polarization selectivity across the spatial domain. Integrating these films as multi-channel optical filters with commercial cameras enables real-time polarimetric detection and imaging, each generating a transmission map from a single exposure. Using deep learning, GOStokes precisely determines arbitrary polarization states with an averaged mean absolute error below 1%. Our demonstration underscores the potential of combining low-cost, scalable, polycrystalline films with reconstruction algorithms for advanced polarimetric applications.

Two-dimensional hybrid metal-halide perovskites (2D-MHPs) have emerged as important solutionprocessed semiconductors with favorable optical and electronic properties for diverse applications in photovoltaics, optoelectronics, and spintronics. The quasi-2D layered structures, featuring large acoustic impedance mismatches between the organic and inorganic sublattices, are expected to result in distinct and anisotropic thermal transport properties along the cross-plane and in-plane directions. Here, we introduce transducer-free vibrational-pump-visible-probe (VPVP) approaches that enable accurate quantification of anisotropic thermal transport properties in various archetypical single-crystalline 2D-MHPs. Specifically, using VPVP spectroscopy and VPVP microscopy, we measure the anisotropic thermal diffusivities of 2D-MHPs with systematically varied Pb-I octahedral layer thicknesses, as well as organic spacer types and lengths, revealing how these structural parameters alter the cross-plane and in-plane thermal transport properties in distinct ways. While diffuse interface scattering plays an important role in dictating cross-plane thermal transport, in-plane thermal transport is primarily determined by phonon transport within interconnected inorganic layers. Density functional theory incorporating four-phonon scatterings provides further insight into the low thermal conductivity and modest thermal conduction anisotropy in 2D-MHPs. Our work demonstrates a new all-optical and noncontact method, which requires minimal sample preparation and allows direct visualization of cross-plane and in-plane thermal transport, potentially compatible with in situ sample environments. The demonstrated VPVP approaches can advance understanding of thermal transport in 2D-MHPs as well as wide-ranging hybrid and polymeric semiconductors beyond 2D-MHPs.

Chiral semiconducting nanomaterials have recently garnered much interest, as their highly favorable chiroptical properties make them exceptional candidates for applications spanning optical communication, 3D displays, and secure encryption. However, their pronounced sensitivity to size, shape, and surface chemistry renders current processing methods highly inconsistent and uncontrollable, limiting further exploration toward these goals. Here, a method is devised to carefully induce and tune the chirality in perovskite nanoplatelets (NPLs) through a polar solvent-assisted chiral ligand exchange while minimizing structural damage to the NPL lattices. Through solvent-engineering, the anisotropic NPLs can also be coerced to self-assemble into highly oriented superlattices, allowing for further control over the chiral NPLs' transition dipole moments. Together, these methods enable circularly polarized luminescence with dissymmetry factors as high as g CPL = 3.4 x 10-2, representing an order of magnitude improvement over their solution-state counterparts. Further, through simultaneous cation exchange with divalent transition metal ions, the quantum yield is successfully boosted by over an order of magnitude and enhance the solution g CPL, demonstrating the versatility of this strategy. These results illustrate this highly general approach for finely tuning the chiroptical properties of perovskite nanomaterials through a single facile and efficient exchange step.

Metal halide perovskite nanoplatelets (NPLs) have demonstrated excellent optical properties for light-emitting applications and achieved tunable blue luminescence through thickness control. However, their translation into electronic devices has lagged behind due to poor colloidal and film stability. The main reason for this is the deprotonation of their surface-capped ammonium passivating ligands, resulting in NPL aggregation. Here we report the first facile synthesis of amine-free pure-blue CsPbBr3 NPLs with outstanding thermal and light stability. This is achieved by utilizing an amine-free phosphine oxide route with a surface capping molecule exhibiting large steric hindrance to prevent NPL aggregation. Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy suggests slower ligand exchange in amine-free NPLs compared to the conventional NPLs, which can be attributed to the strong binding strength of the designated ligand. Consequently, the amine-free NPLs exhibited superior stability against radiation, heat and moisture. We further demonstrate the importance of acid-base equilibrium in this amine-free synthesis route. Through solvent neutralization and passivation with various alkali carbonates, the resulting NPLs attained near-unity photoluminescence quantum yield (PLQY) and pure blue emission.

Nitride ferroelectrics have recently emerged as promising alternatives to oxide ferroelectrics due to their compatibility with mainstream semiconductor processing. ScAlN, in particular, has exhibited remarkable piezoelectric coupling strength (K2) comparable to that of lithium niobate, making it a valuable choice for RF filters in wireless communications. Recently, ScAlN has sparked interest in its use for nanophotonic devices, chiefly due to its large bandgap facilitating operation in blue wavelengths coupled with promises of enhanced nonlinear optical properties such as a large second-order susceptibility (χ(2)). It is still an open question whether ScAlN can outperform oxide ferroelectrics concerning the Pockels effect-an electro-optic coupling extensively utilized in optical communications devices. In this paper, we present a comprehensive theoretical analysis and experimental demonstration of ScAlN's Pockels effect. Our findings reveal that the electro-optic coupling of ScAlN, despite being weak at low Sc concentration, may be significantly enhanced and exceed LiNbO3 at high levels of Sc doping, which points the direction of continued research efforts to unlock the full potential of ScAlN.

Electrical energy is essential for modern society to sustain economic growths. The soaring demand for the electrical energy, together with an awareness of the environmental impact of fossil fuels, has been driving a shift towards the utilization of solar energy. However, traditional solar energy solutions often require extensive spaces for a panel installation, limiting their practicality in a dense urban environment. To overcome the spatial constraint, researchers have developed transparent photovoltaics (TPV), enabling windows and facades in vehicles and buildings to generate electric energy. Current TPV advancements are focused on improving both transparency and power output to rival commercially available silicon solar panels. In this review, we first briefly introduce wavelength- and non-wavelength-selective strategies to achieve transparency. Figures of merit and theoretical limits of TPVs are discussed to comprehensively understand the status of current TPV technology. Then we highlight recent progress in different types of TPVs, with a particular focus on solution-processed thin-film photovoltaics (PVs), including colloidal quantum dot PVs, metal halide perovskite PVs and organic PVs. The applications of TPVs are also reviewed, with emphasis on agrivoltaics, smart windows and facades. Finally, current challenges and future opportunities in TPV research are pointed out.

In recent years, the field of metal-halide perovskite emitters has rapidly emerged as a new community in solid-state lighting. Their exceptional optoelectronic properties have contributed to the rapid rise in external quantum efficiencies (EQEs) in perovskite light-emitting diodes (PeLEDs) from <1% (in 2014) to approaching 30% (in 2023) across a wide range of wavelengths. However, several challenges still hinder their commercialization, including the relatively low EQEs of blue/white devices, limited EQEs in large-area devices, poor device stability, as well as the toxicity of the easily accessible lead components and the solvents used in the synthesis and processing of PeLEDs. This roadmap addresses the current and future challenges in PeLEDs across fundamental and applied research areas, by sharing the community's perspectives. This work will provide the field with practical guidelines to advance PeLED development and facilitate more rapid commercialization.

Metallic catalyst modification by organic ligands is an emerging catalyst design in enhancing the activity and selectivity of electrocatalytic carbon dioxide (CO2) reactive capture and reduction to value-added fuels. However, a lack of fundamental science on how these ligand-metal interfaces interact with CO2 and key intermediates under working conditions has resulted in a trial-and-error approach for experimental designs. With the aid of density functional theory calculations, we provided a comprehensive mechanism study of CO2 reduction to multicarbon products over aminothiolate-coated copper (Cu) catalysts. Our results indicate that the CO2 reduction performance was closely related to the alkyl chain length, ligand coverage, ligand configuration, and Cu facet. The aminothiolate ligand-Cu interface significantly promoted initial CO2 activation and lowered the activation barrier of carbon-carbon coupling through the organic (nitrogen (N)) and inorganic (Cu) interfacial active sites. Experimentally, the selectivity and partial current density of the multicarbon products over aminothiolate-coated Cu increased by 1.5-fold and 2-fold, respectively, as compared to the pristine Cu at -1.16 VRHE, consistent with our theoretical findings. This work highlights the promising strategy of designing the ligand-metal interface for CO2 reactive capture and conversion to multicarbon products.

Colloidal quantum dots (CQDs) are promising materials for infrared (IR) light detection due to their tunable bandgap and their solution processing; however, to date, the time response of CQD IR photodiodes is inferior to that provided by Si and InGaAs. It is reasoned that the high permittivity of II-VI CQDs leads to slow charge extraction due to screening and capacitance, whereas III-Vs-if their surface chemistry can be mastered-offer a low permittivity and thus increase potential for high-speed operation. In initial studies, it is found that the covalent character in indium arsenide (InAs) leads to imbalanced charge transport, the result of unpassivated surfaces, and uncontrolled heavy doping. Surface management using amphoteric ligand coordination is reported, and it is found that the approach addresses simultaneously the In and As surface dangling bonds. The new InAs CQD solids combine high mobility (0.04 cm2 V-1 s-1 ) with a 4× reduction in permittivity compared to PbS CQDs. The resulting photodiodes achieve a response time faster than 2 ns-the fastest photodiode among previously reported CQD photodiodes-combined with an external quantum efficiency (EQE) of 30% at 940 nm.

Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~102 cm2 s-1) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10-1-1 cm2 s-1). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.

Semiconducting thin films made from nanocrystals hold potential as composite hybrid materials with new functionalities. With nanocrystal syntheses, composition can be controlled at the sub-nanometer level, and, by tuning size, shape, and surface termination of the nanocrystals as well as their packing, it is possible to select the electronic, phononic, and photonic properties of the resulting thin films. While the ability to tune the properties of a semiconductor from the atomistic- to macro-scale using solution-based techniques presents unique opportunities, it also introduces challenges for process control and reproducibility. In this review, we use the example of well-studied lead sulfide (PbS) nanocrystals and describe the key advances in nanocrystal synthesis and thin-film fabrication that have enabled improvement in performance of photovoltaic devices. While research moves forward with novel nanocrystal materials, it is important to consider what decades of work on PbS nanocrystals has taught us and how we can apply these learnings to realize the full potential of nanocrystal solids as highly flexible materials systems for functional semiconductor thin-film devices. One key lesson is the importance of controlling and manipulating surfaces.

Metal halide perovskites and colloidal quantum dots (QDs) are two emerging classes of photoactive materials that have attracted considerable attention for next-generation high-performance solution-processed solar cells.

Understanding and controlling carrier dynamics in colloidal quantum dot (CQD) solids is crucial for unlocking their full potential for optoelectronic applications. The recent development of solution-processing methods to incorporate CQDs into high-mobility semiconducting matrices opens new routes to control simultaneously electronic coupling and packing uniformity in CQD solids. However, the fundamental nature of carrier transport in such systems remains elusive. Here we report the direct visualisation of carrier propagation in metal-halide exchanged PbS CQD solids and quantum-dot-in-perovskite (QDiP) heterostructures via transient absorption microscopy. We reveal three distinct transport regimes: an initial band-like transport persisting over hundreds of femtoseconds, an Auger-assisted sub-diffusive transport before thermal equilibrium is achieved, and a final hopping regime at longer times. The band-like transport was observed to correlate strongly with the extent of carrier delocalisation and the degree of energetic disorder. By tailoring the perovskite content in heterostructures, we obtained a band-like transport length of 90 nm at room temperature and an equivalent diffusivity of up to 106 cm 2 s -1 – which is four orders of magnitude higher than the steady-state values obtained for PbS CQD solids. These findings not only shed light on the non-equilibrium dynamics in CQD solids and their influence on carrier transport, but also introduce promising strategies to harness non-equilibrium transport phenomena for more efficient optoelectronic devices.