Full Passivation Research Articles

Optimizing strategy of bifacial TOPCon solar cells with front-side local passivation contact realized by numerical simulation

The tunnelling oxide passivation contact (TOPCon) solar cells have been impressive in the global photovoltaic (PV) market originating from their high efficiency and stability. However, it exhibits significant recombination losses due to its boron diffusion, laser damage and metal-semiconductor contact on front side. The bifacial TOPCon structure demonstrates massive potential in the improvement of passivation and contact performance with the premise that it can solve the parasitic absorption of polycrystalline silicon (poly-Si). In this study, the localized poly finger structure with excellent optics and passivation performance is designed in the front side of bifacial solar cells to compare with traditional TOPCon and full-area poly passivation devices. The theoretical efficiency and detailed power loss analysis in our simulation reveal that suppressing the recombination of FSF (front surface field) and the contact area is the crucial strategy to improve device performance, with optimized efficiency of 26.62 % and FF of 85.16 %. These results indicate that the route of BJ (back junction) structure containing localized selective contact and full coverage high-quality passivation holds potential in realizing both high Jsc and Voc for FBC (front and back contact) solar cells, featuring great instructive significance for future industrialization of PV production.

Molecular Design Engineering Regulates the Ground-State Passivation Ability of Benzophenone Derivatives in Perovskite Solar Cells.

Intramolecular hydrogen bonding (H-bonding) involved in the excited-state proton transfer (ESPT) process results in benzophenone derivatives (BPDs) with an excellent ability to passivate defects. However, the BPDs are in a continuing dynamic transition process between the ground state and the excited state under light radiation conditions. The ground-state BPDs may lose their ability to passivate defects, resulting in an increased defect density of the perovskite. Therefore, enhancing the passivation ability of the ground-state BPDs can help to achieve the full passivation ability of their ground state to excited state. Herein, we have researched the various BPDs by density functional theory and found that intramolecular H-bonding can weaken the passivation ability of ground-state BPDs, but intramolecular H-bonding is indispensable in the ESPT process. To address the issue, we investigated the influence of electron-donor properties and dipole moments of hydroxyl (-OH), methoxy (-OCH3), and n-octyloxy (-OC8H17) groups in BPD molecules on their coordination capacity through molecular design engineering. Ultimately, 2-hydroxy-4-n-octyloxy-benzophenone (UV5) with strong electron-donor n-octyloxy (-OC8H17) and elongated carbon-chain structure was selected as an additive, which enhances the passivate defect capability in both the ground and excited states. As a result, the UV5-based champion device achieved a power conversion efficiency (PCE) of 24.46% and remained at 75% of the initial PCE with exposure to UV light. This work focuses on the defect passivation capability of ground-state BPDs for the first time and opens a new concept for applying BPDs in PSCs.

A theoretical study of surface lithium effects on the [111] SiC nanowires as anode materials.

Silicon carbide nanowires (SiCNWs) are considered a promising alternative material for application in lithium-ion batteries, with researchers striving to develop new electrode materials that exhibit high capacity and high charge/discharge rate performance. To gain a deeper understanding of the application of SiCNWs in semiconductor material science and energy supply fields, we investigated the effects of nanoscale and surface lithiation on the electrical and mechanical properties of SiCNWs grown along the [111] direction. First-principles calculation was used to study their geometries, electronic structures, and associated electrochemical properties. Herein, we considered SiCNWs with full hydrogen passivation, full lithium passivation, and mixed passivation at different sizes. The formation energy indicates that the stability of SiCNWs increases with the increasing diameter, and the surface-lithiated SiC nanowires (Li-SiCNWs) are found to be energetically stable. The mixed passivated SiCNWs exhibit the properties of indirect band gap with the increase of lithium atoms on the surface, while the fully lithium passivated nanowires exhibit metallic behavior. Charge analysis shows that a portion of the electrons on the lithium atoms are transferred to the surface atoms of the nanowires and electrons prefer to cluster more near the C atoms. Additionally, Li-SiCNWs still have good mechanical resistance during the lithiation process. The stable open-circuit voltage range and theoretical capacity of these SiCNWs indicate their suitability as anode materials. In this study, Materials Studio 8.0 was used to construct the models of the SiCNWs. And all the density functional theory (DFT) calculations were performed by the Vienna ab initio Simulation Package (VASP). The self-consistent field calculations are performed over a Monkhorst-Pack net of 1 × 1 × 6k-points. The energy convergence criteria for the self-consistent field calculation were set to 10-5eV/atom with a cutoff energy of 400eV.

Investigation on the Passive Behavior of Ti-9Mn Alloy in 3.5 wt% NaCl Solution

Ti-9Mn alloy, widely used in aerospace and hydrogen storage, was recently introduced for marine and offshore structures because of its competitive mechanical characteristics. In this study, passive behavior of Ti-9Mn alloy was compared to the commercially pure titanium (cp-Ti). Ti-9Mn exhibited lower charge-transfer resistance than cp-Ti. Under steady-state condition, resistivity at metal/oxide film interface for Ti-9Mn alloy, which increased as fa unction of applied passive potential in range of 0.5 to 1.5 VSCE, was found to be lower than that of cp-Ti. Complex-capacitance (C ∞) value for Ti-9Mn alloy was higher than that of cp-Ti. Presence of Mn in the alloy induced significant increase in current density when potential exceeds 1.5 VSCE. Corrosion current density of Ti-9Mn (16.2 ± 4.0 nA cm−2) was three times higher than that of cp-Ti (4.57 ± 0.7 nA cm−2) after 21 days immersion in 3.5 wt% NaCl. The study may allow us to realize the full potential passivation behavior of Ti-9Mn for future marine and offshore applications.

Investigation of sub-stoichiometric MoOx hole-selective contacts for rear junction passivating contact silicon solar cells

Carrier-selective contacts play a crucial role in improving the performance of silicon solar cells by reducing recombination losses. This study explores the use of sub-stoichiometric molybdenum oxide (MoOx) as a hole-selective contact material deposited via thermal evaporation. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) analysis reveal diverse Mo–O bonding configurations and a low work function of ∼5.02 eV for the MoOx film. The passivation properties of a cell-like structure with local MoOx contact are found to be comparable to those of a structure with a full front passivation layer, as evidenced by an implied open-circuit voltage (iVoc) of 703.2 mV. However, the conversion efficiency of the solar cell with MoOx contact is limited to 16.5 %, with reduced external quantum efficiency (EQE) at UV and visible wavelengths. The study proposes that optimizing the MoOx front contact's work function and passivation characteristics could improve the solar cell's efficiency to 21.8 %. This research demonstrates the potential of sub-stoichiometric MoOx as a promising hole-selective contact for silicon solar cells, highlighting the factors influencing its performance.

Nanotribological Properties of Oxidized Diamond/Silica Interfaces: Insights into the Atomistic Mechanisms of Wear and Friction by Ab Initio Molecular Dynamics Simulations.

Controlling friction and wear at silica-diamond interfaces is crucial for their relevant applications in tribology such as micro-electromechanical systems and atomic force microscopes. However, the tribological performance on diamond surfaces is highly affected by the working environment where atmospheric gases are present. In this work, we investigate the effects of adsorbed oxygen on the friction and wear of diamond surfaces sliding against silica by massive ab initio molecular dynamics simulations. Different surface orientations, O-coverages, and tribological conditions are considered. The results suggest that diamond surfaces with full oxygen passivation are very effective in preventing surface adhesion, and as a result present extremely low friction and wear. At low oxygen coverage, Si-O-C bond formation was observed as well as atomistic wear initiated from C-C bond breaking at extreme pressure. The analysis of electronic structures of the configurations resulting from key tribochemical reactions clarifies the mechanisms of friction reduction and atomistic wear. Overall, our accurate in silico experiments shed light on the influence of adsorbed oxygen on the tribological properties and wear mechanisms of diamond against silica.

The Comprehension and Production of Passive Constructions by Afrikaans and isiXhosa First Language Grade 1 Children

ABSTRACT The acquisition of passives is well-studied in many languages, with evidence of crosslinguistic differences in the age at which passives are acquired. The aim of this study is to add to the existing knowledge of child acquisition of passives by providing data from Afrikaans and isiXhosa, two under-researched and typologically different languages spoken in South Africa. Comprehension and production data were collected from first language speakers (27 Afrikaans; 29 isiXhosa) from low socioeconomic backgrounds at the beginning and end of their Grade 1 year (aged 6;0 to 7;6). Picture selection and sentence completion tasks of the Receptive and Expressive Activities for Language Therapy were used to collect comprehension and production data, respectively, on short/full passives with actional verbs, reversible passives, and passives containing perceptual and psychological verbs. Comprehension of short passives with actional verbs were fully acquired by the isiXhosa L1 groups and reversible passives were approaching mastery by the beginning of Grade 1, but not the comprehension or production of any other types of passives constructions, by neither the isiXhosa nor the Afrikaans L1 group. By the end of the Grade 1 year, the isiXhosa group had acquired full comprehension and production of all passive types, whereas the Afrikaans group had fully acquired comprehension of both short and full passives with actional verbs but not yet passive production. Language group differences are thought to be related, in part, to differences in passive morphosyntax.

Unraveling the passivation mechanisms of c-Si/SiOx/poly-Si contacts

As one of the prospective crystalline silicon (c-Si) technologies, tunnel oxide passivating contact (TOPCon) solar cells have recently attracted much attention in the photovoltaic community. However, the deficit of open-circuit voltage due to the imperfect passivation performance together with the insufficient understanding of the passivation mechanism, especially for the key structures of TOPCon devices ( i.e. , poly-Si/SiO x /c-Si), is a crucial factor to limit the improvement of device efficiency. To unlock the full passivation potential of this type of poly-Si/SiO x /c-Si contact, we report a systematic investigation by combining experiments and simulations. The related results can be summarized: 1) the best passivation can be obtained by optimizing SiO x quality, tailoring the in-diffusion profile, and performing hydrogenation; 2) if SiO x quality is good enough, high-level passivation can be expected even without impurity doping; 3) although the deepened in-diffusion could partially alleviate the degradation of the poor surface passivation, it would also reduce the passivation performance owing to the increased Auger recombination inherent to the high impurity doping; 4) the presence of pinholes would degrade the passivation performance, especially for the cases with the good surface passivation, a shallow in-diffusion and a low doping concentration of poly-Si, where the electric-field effect was minimized. To further confirm these conclusions, recombination distributions and the corresponding current profiles of the minority carriers were reviewed. This work clarifies the passivation mechanism of c-Si/SiO x /poly-Si contact in detail and provides effective guidance for further promoting the passivation level and the efficiencies of TOPCon devices. • An experiment and complementary simulations were designed to confirm the passivation properties of c-Si/SiO x /poly-Si contacts. • Annealing temperature, hydrogenation and SiO x quality were simultaneously regulated to promote passivation quality. • The underlying factors including poly-Si thickness and pinholes to affect the passivation performance were investigated in detail. • Passivation mechanisms were clarified by addressing recombination distributions and current profiles of the minority carriers.

Applying Hydrogenation to Stabilize N-TiO2 and Enhance Its Visible Light Photocatalytic Activity

Up to now, the explanation for the origin of enhanced photocatalytic activity of N doped TiO2 (N-TiO2) with H incorporation, which is observed in experiment, is still lacking. In our work, the effects of hydrogenation on the stability and electronic properties of N-TiO2 have been systematically investigated by first-principles calculations. Our results of the study on stability demonstrate that, both full and part hydrogenation could stabilize N-TiO2 by largely reducing the formation energy of N doping under Ti-rich conditions. Moreover, the calculated results on the electronic structure show that, for the completely hydrogenated N-TiO2, band gap becomes slightly larger, which is caused by the full passivation for unpaired electron from N atom. However, for the partially hydrogenated N-TiO2, due to the interaction between hydrogenated and unhydrogenated N atoms, its valence band maximum shifts to higher energy by 0.32 eV and the valence band states mix with the wide band-gap states, which results in a higher light absorption capacity and carrier separation. Our results not only explain the enhancement of visible light photocatalytic activity experimentally found in N-TiO2 specimen with H incorporation, but also indicate that, tuning the hydrogenation degree is a hopeful routine to improve the photocatalytic performance of N-TiO2.

Densification of Diazonium-Based Organic Thin Film as Bioelectrical Interface.

Aryl diazonium chemistry generates a covalently attached thin film on various materials. This chemistry has diverse applications owing to the stability, ease of functionalization, and versatility of the film. However, the uncontrolled growth into a polyaryl film has limited the controllability of the film's beneficial properties. In this study, we developed a multistep grafting protocol to densify the film while maintaining a thickness on the order of nanometers. This simple protocol enabled the full passivation of a nitrophenyl polyaryl film, completely eliminating the electrochemical reactions at the surface. We then applied this protocol to the grafting of phenylphosphorylcholine films, with which the densification significantly enhanced the antifouling property of the film. Together with its potential to precisely control the density of functionalized surfaces, we believe this grafting procedure will have applications in the development of bioelectrical interfaces.

Operando characterization of active surface area and passivation effects on sulfur-carbon composites for lithium-sulfur batteries

Sulfur electrodes for lithium-sulfur batteries necessarily contain a conductive additive, typically carbon, to enable the electrochemical reactions, since sulfur and the discharge product, Li2S, are insulators. Consequently, the full passivation of carbon, by deposition of sulfur and/or Li2S, would necessarily produce the death of the battery. However, here we demonstrate that for high-performance lithium-sulfur batteries operated under lean electrolyte conditions (electrolyte to sulfur ratio of 6 µL mgS−1 in Li-S coin cells), the extent of passivation of carbon is not severe enough to limit performance. This is shown by performing impedance measurements of fully charged lithium-sulfur batteries, from which we demonstrate that we can evaluate the specific surface area of carbon, and we find that the capacity fade with cycling is not due to a decrease in the electrochemically active surface area of carbon. These results show that introducing a higher surface area carbon in the sulfur electrode formulation is not needed to prevent passivation, and that the focus of lithium-sulfur development should be directed towards other issues, such as mitigating undesirable reactions at the lithium electrode and achieving robust sulfur electrode structures enabling fast transport of electrolyte species and, thus, more homogeneous reactions.

Full Defects Passivation Enables 21% Efficiency Perovskite Solar Cells Operating in Air

AbstractThe lattice defects in the bulk and on the surface of the halide perovskite layer serve as trap sites and recombination centers to annihilate photogenerated carriers, determining the performance and stability of perovskite optoelectronic devices. Herein, the previously reported surface defects passivation engineering is extended to a full defects passivation strategy through stereoscopically introducing the cysteamine hydrochloride (CSA‐Cl) in the bulk and on the surface of perovskites. First‐principle density functional theory (DFT) calculations are employed to theoretically verify the multiple defects passivation effect of the CAS‐Cl on the perovskite. The perovskite layer with full defects passivation exhibits superior carrier dynamics as revealed by femtosecond transient absorption due to the reduced defect density determined by a highly sensitive photothermal deflection spectroscopy technique. Consequently, a high efficiency approaching 21% is achieved for the inverted planar perovskite solar cells (PVSCs). More importantly, the CAS‐Cl passivated PVSCs exhibit operation in air, which will be beneficial for the in situ device test for understanding the photophysics involved. This work provides a promising strategy to reduce the defects in both the perovskite bulk and surface for superior optoelectronic properties, facilitating the development of highly efficient and stable PVSCs and other optoelectronic devices.

Tuneable Functionalization of Glass Fibre Membranes with ZnO/SnO2 Heterostructures for Photocatalytic Water Treatment: Effect of SnO2 Coverage Rate on the Photocatalytic Degradation of Organics

The construction of a ZnO/SnO2 heterostructure is considered in the literature as an efficient strategy to improve photocatalytic properties of ZnO due to an electron/hole delocalisation process. This study is dedicated to an investigation of the photocatalytic performance of ZnO/SnO2 heterostructures directly synthesized in macroporous glass fibres membranes. Hydrothermal ZnO nanorods have been functionalized with SnO2 using an atomic layer deposition (ALD) process. The coverage rate of SnO2 on ZnO nanorods was precisely tailored by controlling the number of ALD cycles. We highlight here the tight control of the photocatalytic properties of the ZnO/SnO2 structure according to the coverage rate of SnO2 on the ZnO nanorods. We show that the highest degradation of methylene blue is obtained when a 40% coverage rate of SnO2 is reached. Interestingly, we also demonstrate that a higher coverage rate leads to a full passivation of the photocatalyst. In addition, we highlight that 40% coverage rate of SnO2 onto ZnO is sufficient for getting a protective layer, leading to a more stable photocatalyst in reuse.

Near-Edge Ligand Stripping and Robust Radiative Exciton Recombination in CdSe/CdS Core/Crown Nanoplatelets.

We address the relation between surface chemistry and optoelectronic properties in semiconductor nanocrystals using core/crown CdSe/CdS nanoplatelets passivated by cadmium oleate (Cd(Ol)2) as model systems. We show that addition of butylamine to a nanoplatelet (NPL) dispersion maximally displaces ∼40% of the original Cd(Ol)2 capping. On the basis of density functional theory simulations, we argue that this behavior reflects the preferential displacement of Cd(Ol)2 from (near)-edge surface sites. Opposite from CdSe core NPLs, core/crown NPL dispersions can retain 45% of their initial photoluminescence efficiency after ligand displacement, while radiative exciton recombination keeps dominating the luminescent decay. Using electron microscopy observations, we assign this robust photoluminescence to NPLs with a complete CdS crown, which prevents charge carrier trapping in the near-edge surface sites created by ligand displacement. We conclude that Z-type ligands such as cadmium carboxylates can provide full electronic passivation of (100) facets yet are prone to displacement from (near)-edge surface sites.

Surface functionalization modulates the structural and optoelectronic properties of two-dimensional Ga2O3

Fabricating low-dimensional ultra-wide-bandgap β-Ga2O3 has been regarded as a promising approach to optimize the performance of β-GaO Ga2O3–based optoelectronics. Controlling the surface-dangling bonds of low-dimensional Ga2O3 is crucial for the performance modulation. Here, the structural stability and optoelectronic properties of two-dimensional (2D) Ga2O3 tuned by halogen passivation are comparatively investigated by density functional theory. No matter how full passivation and semipassivation, both chlorine and fluorine passivation can change the indirect bandgap into direct bandgap for 2D Ga2O3 because of the higher energy of bonding orbital for Ga-halogen bond than that of Ga–O bond. Moreover, surface chlorine passivation promotes the formation of p-type 2D Ga2O3 with reduced bandgap because chlorine passivation supplies electron to Ga2O3, while fluorine passivation introduces some subconduction bands into the enlarged bandgap because of the π∗ antibonding between the F-py and O-py orbitals. In addition, just chlorine passivation can simultaneously improve the electron and hole mobility of 2D Ga2O3, while opposite characters are observed for fluorine-passivated 2D Ga2O3. The hole mobility of chlorine semipassivated p-type monolayer Ga2O3 along b direction increases to 3913.52 cm2V−1s−1. Moreover, surface chlorine passivation not only enhances the absorption in the ultravisible region but also extends the absorption range of 2D Ga2O3 from the ultravisible to visible region. Note that the fluorine-passivated 2D Ga2O3 has more stability than the chlorine-passivated one. This work deeply reveals the effect of surface halogen passivation and provides useful guidance for realizing high-performance p-type Ga2O3 optoelectronics.

Tailoring the electrochemical properties of 2D-hBN via physical linear defects: physicochemical, computational and electrochemical characterisation.

Monolayer hexagonal-boron nitride films (2D-hBN) are typically reported within the literature to be electrochemically inactive due to their considerable band gap (ca. 5.2–5.8 eV). It is demonstrated herein that introducing physical linear defects (PLDs) upon the basal plane surface of 2D-hBN gives rise to electrochemically useful signatures. The reason for this transformation from insulator to semiconductor (inferred from physicochemical and computational characterisation) is likely due to full hydrogenation and oxygen passivation of the boron and/or nitrogen at edge sites. This results in a decrease in the band gap (from ca. 6.11 to 2.36/2.84 eV; theoretical calculated values, for the fully hydrogenated oxygen passivation at the N or B respectively). The 2D-hBN films are shown to be tailored through the introduction of PLDs, with the electrochemical behaviour dependent upon the surface coverage of edge plane-sites/defects, which is correlated with electrochemical performance towards redox probes (hexaammineruthenium(iii) chloride and Fe2+/3+) and the hydrogen evolution reaction. This manuscript de-convolutes, for the first time, the fundamental electron transfer properties of 2D-hBN, demonstrating that through implementation of PLDs, one can beneficially tailor the electrochemical properties of this nanomaterial.

Role of Surface Reduction in the Formation of Traps in n-Doped II-VI Semiconductor Nanocrystals: How to Charge without Reducing the Surface.

The efficiency of nanocrystal (NC)-based devices is often limited by the presence of surface states that lead to localized energy levels in the bandgap. Yet, a complete understanding of the nature of these traps remains challenging. Although theoretical modeling has greatly improved our comprehension of the NC surface, several experimental studies suggest the existence of metal-based traps that have not yet been found with theoretical methods. Since there are indications that these metal-based traps form in the presence of excess electrons, the present work uses density functional theory (DFT) calculations to study the effects of charging II–VI semiconductor NCs with either full or imperfect surface passivation. It is found that charge injection can lead to trap-formation via two pathways: metal atom ejection from perfectly passivated NCs or metal–metal dimer-formation in imperfectly passivated NCs. Fully passivated CdTe NCs are observed to be stable up to a charge of two electrons. Further reduction leads to charge localization on a surface Cd atom and the formation of in-gap states. The effects of suboptimal passivation are probed by charging NCs where an X-type ligand is removed from the (100) plane. In this case, injection of even one electron leads to Cd-dimerization and trap-formation. Addition of an L-type amine ligand prevents this dimer-formation and is suggested to also prevent trapping of photoexcited electrons in charge neutral NCs. The results presented in this work are generalized to NCs of different sizes and other II–VI semiconductors. This has clear implications for n-doping II–VI semiconductor NCs without introducing surface traps due to metal ion reduction. The possible effect of these metal ion localized traps on the photoluminescence efficiency of neutral NCs is also discussed.

Passivity Based Damping Design for Grid-Connected Converter With Improved Stability

The impedance interactions between weak grid and LCL-filtered converter can bring severe harmonic resonance. Recently, frequency domain passivity theory has been applied to converter damping design. However, it is usually not easy to achieve full frequency passivity. What’s more, traditional passivity based damping design is not enough for system robustness. This paper first proposes a relaxed passivity based active damping design for capacitor current feedback. Then the system stability under grid impedance variation is also analyzed. It has been found that the wide variation of grid impedance can decrease system stability margin. As a result, critical oscillation can even happen in the passive region of converter output admittance, causing power quality problems. In order to further improve system stability, this paper proposes an enhanced passivity based impedance shaping method, which is based on hybrid damping and combined active damping. Effects of damping methods and damping parameters are also investigated. A step by step damping design procedure is formulated, which is easy to implement. Simulation and experimental results validate the effectiveness of proposed method.

Design Principles for Trap-Free CsPbX3 Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer Lewis Bases.

We introduce a general surface passivation mechanism for cesium lead halide perovskite materials (CsPbX3, X = Cl, Br, I) that is supported by a combined experimental and theoretical study of the nanocrystal surface chemistry. A variety of spectroscopic methods are employed together with ab initio calculations to identify surface halide vacancies as the predominant source of charge trapping. The number of surface traps per nanocrystal is quantified by 1H NMR spectroscopy, and that number is consistent with a simple trapping model in which surface halide vacancies create deleterious under-coordinated lead atoms. These halide vacancies exhibit trapping behavior that differs among CsPbCl3, CsPbBr3, and CsPbI3. Ab initio calculations suggest that introduction of anionic X-type ligands can produce trap-free band gaps by altering the energetics of lead-based defect levels. General rules for selecting effective passivating ligand pairs are introduced by considering established principles of coordination chemistry. Introducing softer, anionic, X-type Lewis bases that target under-coordinated lead atoms results in absolute quantum yields approaching unity and monoexponential luminescence decay kinetics, thereby indicating full trap passivation. This work provides a systematic framework for preparing highly luminescent CsPbX3 nanocrystals with variable compositions and dimensionalities, thereby improving the fundamental understanding of these materials and informing future synthetic and post-synthetic efforts toward trap-free CsPbX3 nanocrystals.

Mistakes weren’t made: Three-year-olds’ comprehension of novel-verb passives provides evidence for early abstract syntax

By about age three, English-learning children begin to understand passive sentences with familiar verbs. We probed the nature of children’s linguistic representations by asking whether 3-year-olds promptly extend their emerging knowledge of the passive structure to novel verbs. In three preferential-looking experiments, 3-year-olds (N = 124) interpreted novel verbs presented in short passives (Experiment 1, “She’s getting snedded!”) as transitive verbs, referring to causal-action rather than solo-action events, and used word-order in full passives, (Experiments 2 and 3, e.g., “She’s getting snedded by the boy!”), to select a target event in which the subject was the patient, not the agent of action. Comprehension accuracy in Experiments 1 and 2 varied with vocabulary, but this vocabulary effect disappeared when children were given more time and more repetitions of the test sentences (Experiment 3). These findings support early-abstraction accounts of acquisition: 3-year-olds represent passive syntax in abstract terms, permitting extension to novel verbs. This, in turn, allows them to use passive sentences to identify the grammatical subcategory and meaning of an unknown verb.