Surface Passivation Research Articles

Calcium nitrate effectively mitigates alkali–silica reaction by surface passivation of reactive aggregates

AbstractCalcium nitrate (CN: Ca(NO3)2) has been shown to mitigate alkali–silica reaction (ASR) in concrete. Such ASR mitigation has been suggested to be on account of precipitate (i.e., barrier or passivation layer) formation‐induced dissolution inhibition of reactive/dissolving aggregate surfaces. Herein, we examine the ability of CN to mitigate ASR across two cements (Type I/II and Portland Limestone Cement), for aggregates of varying reactivity, and across different types and dosages of SCMs (supplementary cementitious materials, i.e., amorphous steel slag and Class C and Class F fly ashes). Based on expansion measurements carried out as per ASTM C1260/C1567, it is observed that CN, as a function of dosage, substantively mitigates ASR in mortar formulations across aggregate types. Careful microstructural examinations, dissolution studies, and thermodynamic calculations indicate that CN induces the formation of C–S–H, portlandite (Ca(OH)2), and calcite (CaCO3) precipitate mixtures, which form on aggregate surfaces at the expense of typical ASR gels. Such precipitates create a dissolution barrier and inhibit ASR in both SCM‐free and SCM‐containing formulations. The outcomes indicate that CN is an efficient and cost‐effective ASR mitigation additive (∼$250–$600 per tonne), particularly in a time of dwindling fly ash supplies and unaffordable lithium prices (>∼$12 000 per tonne).

Effective surface treatment for efficient and stable inverted inorganic CsPbI2Br perovskite solar cells

The interest in all-inorganic perovskite solar cells (PSCs) featuring a p-i-n structure is on the rise, attributed to their superior heat resistance and adaptability with tandem cell methods. However, their progress has been far from the regular structure owing to the comparatively low open circuit voltage (Voc). This research employs phenylethylammonium iodide, incorporating various side groups, as passivators to tackle the previously mentioned problems and investigate their effects on passivation. It is found that a reduction of trap-state density in perovskite film was accomplished due to the PEAI effective passivation effect by establishing coordination with the under-coordinated Pb2+ ions. Furthermore, there was an enhancement in the alignment of energy levels at the CsPbI2Br perovskite/PCBM junction, resulting in better charge extraction from the CsPbI2Br layer to the charge transport layer. As a result, an improved champion efficiency of 14.26 % with a Voc of 1.11 V, Jsc of 16.21 mA/cm2, and FF of 79.28 % was yielded for the PEAI treatment inverted CsPbI2Br device, compared with the 12.15 % efficiency of the control device. Superior device stability was exhibited for the optimal PEAI-treated devices without encapsulation. This research validates the significance of a side group on a surface passivation molecule to effectively passivate defects and optimize energy levels, especially for boosting Voc.

Research on the Performance of Fmoc-amino Acid Passivated Peroverskite Solar Cells

This study investigates the effect of surface passivation of chalcogenide solar cells by introducing Fmoc-Gly-OH amino acids. The results show that the moderate amount of Fmoc-Gly-OH modification can significantly improve the photovoltaic performance and stability of chalcogenide solar cells. With the increase of Fmoc-Gly-OH concentration, the photovoltaic conversion efficiency firstly increases and then decreases, and the best effect is reached when the concentration is 1.0 mg/ml.XRD and SEM analyses show that the crystal structure of the Fmoc-Gly-OH modified chalcocite thin films is more regular, and the defect density is obviously reduced.XPS analysis shows that the Fmoc-Gly-OH modification is able to reduce the defect state density of the chalcogenide layer. The reduction of defects was further verified by steady-state fluorescence spectroscopy analysis. In addition, the electrochemical impedance spectra and dark-state I-V curve results of the devices showed that the Fmoc-Gly-OH modification was able to reduce the non-radiative complexation and charge transport resistance, and increase the fill factor and open-circuit voltage. Finally, the effectiveness of Fmoc-Gly-OH surface passivation in enhancing the performance of chalcogenide solar cells was confirmed by the analysis of J-V curves and box plots. This study provides new ideas and methods for surface engineering of chalcogenide solar cells, which has some practical application prospects.

Soft X-ray performance of an optimised charge-coupled device for astronomy

For the upcoming European Space agency (ESA)/Chinese Academy of Sciences (CAS) SMILE mission, launching in 2025, large-format soft X-ray optimised CCDs have been manufactured by Teledyne e2v, named the CCD370. The CCDs are approximately 8 cm × 8 cm and are comprised of 4510 × 4510 18 μm pitch pixels, with a store shield covering approximately 1/7th of the active imaging area to facilitate frame-transfer operation mode. To optimise quantum efficiency within the soft X-ray energy band, the device is 16 μm thick, back illuminated, and has an additional back surface passivation process. The focal plane of the soft X-ray imager (SXI) on the SMILE spacecraft will be comprised of 2 CCD370s, operating with 6 × 6 on-chip binning to mitigate against CTI-induced charge transfer losses and charge spreading throughout the 3-year mission lifetime.As part of the pre-flight testing and calibration, a CCD370 was characterised at the PTB beamline at the BESSY 2 synchrotron in Berlin, and key metrics such as quantum efficiency and energy resolution in the 0.2–1.8 keV energy band were assessed. The quantum efficiency measurements show expected performance within specification for the instrument, and also match a transmission-layer QE model. The energy resolution is 68 ± 2 eV FWHM @ 1.2 keV, which is an improvement over the current generation of X-ray telescopes such as XMM-Newton, Chandra, and the Swift X-ray Telescope. Although competing technologies such as DEPFETs and scientific CMOS image sensors now have similar performance to CCDs, the performance shown here can still easily satisfy requirements for novel X-ray instruments, and can still be useful in future astronomy missions given the rich heritage, high technology-readiness-level, and maturity of the technology.

Illuminating Pathways to Dynamic Nanotribology: Light-Mediated Active Control of Interfacial Friction with Nanosuspensions.

Active control of nanotribological properties is a challenge. Materials responsive to external stimuli may catalyze this paradigm shift. Recently, the nanofriction of a thin film is modulated by light, ushering in phototribology. This frontier is expanded here, by investigating photoactive nanoparticles in lubricants to confer similar functionality to passive surfaces. Quartz-crystal microbalance (QCM) is employed to assess the phototribological behavior of aqueous suspensions of titanium dioxide nanoparticles. A comparison of dark and illuminated conditions provides the first demonstration of tuning the interfacial friction in solid-nanosuspension interfaces by light. Cyclic tests reveal reversible transitions between higher (dark) and lower friction (illuminated) regimes. These transitions are underpinned by transient states with surface charge variations, as confirmed by Zeta potential measurements. The accumulated surface charge increases repulsion within the system and favors sliding. Upon cessation of illumination, the system returns to its prior equilibrium state. These findings impact not only nanotribology but nanofluidics and nanorheology. Furthermore, the results underscore the need to consider light-induced effects in other scenarios, including the calculation of activity coefficients of photoactive suspensions. This multifaceted study introduces a new dimension to in operando frictional tuning, beckoning a myriad of applications and fundamental insights at the nanoscale.

TCAD simulation of germanium-based heterostructure solar cell employing molybdenum oxide as a hole-selective layer

Molybdenum Oxide (MoO x ) has been used as a hole-extraction film for photovoltaic (PV) applications; however, its interaction with Germanium (Ge)-based solar cells is less understood. For the first time, this paper aims to physically model the Ge solar cell that incorporates MoO x for hole transportation at the front side of the PV device facing the sunlight. However, the charge transportation process within the PV device is influenced by several design parameters that need optimization. A higher work function of MoO x increases the barrier height against minority carriers of electrons which is beneficial for extricating holes at the front interface of MoO x /Ge. A progressive reduction in the recombination of charge carriers has been observed by including a passivation layer of amorphous silicon (i-a-Si:H). Similarly, inserting a passivation and back surface field (BSF) stack of i-a-Si:H strengthens the electric field and likewise reduces the recombination at the rear side of the device. An enhanced doping concentration of BSF assists in the favorable alignment of energy bands for improved charge transportation within the solar cell as the rear passivation maintains the field strength for accelerated movement of charge carriers. However, optimizing the thickness of the front-passivation film is challenging due to the parasitic absorption of light at larger thicknesses. A comparative study with the reference device revealed that the proposed device exhibited a step-increase in the conversion efficiency (η) from 4.23% to 13.10%, with a higher J sc of 46.4 mA cm−2, V oc of 383 mV, and FF of 74%. The proposed study is anticipated to meet the research gap in the physical device modelling of Ge-based solar cells employing high work function MoO x as a carrier-selective layer that could be conducive to the development of highly efficient multijunction solar cells.

Recent Functionalized Strategies of Metal-Organic Frameworks for Anode Protection of Aqueous Zinc-Ion Battery.

The inherent benefits of aqueous Zn-ion batteries (ZIBs), such as environmental friendliness, affordability, and high theoretical capacity, render them promising candidates for energy storage systems. Nevertheless, the Zn anodes of ZIBs encounter severe challenges, including dendrite formation, hydrogen evolution reaction, corrosion, and surface passivation. These would result in the infeasibility of ZIBs in practical situations. To this end, artificial interfaces with functionalized materials are crafted to protect the Zn anode. They have the capability to modulate the zinc ion flux in proximity to the electrode surface and shield it from aqueous electrolytes by leveraging either size effects or charge effects. Considering metal-organic frameworks (MOFs) with tunable pore size, chemical composition, and stable framework structures, they have emerged as effective materials for building artificial interfaces, prolonging the lifespan, and improving the unitization of Zn anode. In this review, the contributions of MOFs for protecting Zn anode, which mainly involves facilitating homogeneous nucleation, manipulating selective deposition, regulating ion and charge flux, accelerating Zn desolvation, and shielding against free water and anions are comprehensively summarized. Importantly, the future research trajectories of MOFs for the protection of the Zn anode are underscored, which may propose new perspectives on the practical Zn anode and endow the MOFs with high-value applications.

Carbon-based films: A review on mechanical and tribology properties

Carbon films have attracted widespread interest for decades thanks to their superior tribomechanical properties. As new carbon allotropes were discovered over time, measurements of elastic modulus reached terapascals, and coefficient of friction thousandths, while the mechanisms that enabled this performance were understood. Yet, research attention on carbon-based films and composites is still increasing by the year. Challenges such as durability and chemical reactivity have been addressed by doping and surface passivation, and the combination of two or more carbon allotropes in a single film, as in merging carbon nanotubes and nanodiamond in forming nanoscrolls, allowed to combine the superior properties of each, achieving a performance which is higher than either material alone. This review is focused on films based on various forms of carbon, including amorphous carbon, diamond-like carbon, graphite, graphene, carbon nanotubes, nanodiamond, fullerenes, and their hybrids. The tribomechanical properties, as well as the underpinning mechanisms than enable them, are explored. The effect of chemical composition, environment, structure, scale and substrate are presented, in relation to performance. Finally, some examples of composite materials whose performance is enabled by the addition of carbon-based materials are presented. Ways forward in the field are identified, in particular within the hybrid and composite materials areas, which have the potential of further increasing applicability and performance of carbon-based films.

Parametric channel estimation for RIS-assisted mmWave MIMO-OFDM systems with low pilot overhead

We consider the channel estimation problem in a millimeter-wave (mmWave) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system aided by a passive reconfigurable intelligent surface (RIS). Initially, leveraging the inherent sparsity of mmWave channels, we decouple the channel estimation into the recovery of multipath parameters, including spatial frequencies of angles, delays, and complex gains. Subsequently, we employ two training schemes: the first involves a full row rank constrained RIS phase shift pattern, and the second incorporates a Kronecker structure constrained RIS phase shift pattern. These schemes reform channel estimation into estimating parameters from two fifth-order tensor signals, which admit constrained Canonical Polyadic decomposition. Moreover, both tensor signals share Vandermonde-constrained factor matrices, enabling algebraic algorithms for tensor decomposition problems and recovering channel multipath parameters. Theoretical analyses show that the first training scheme has a lower signal processing complexity for channel estimation, while the second attains a higher estimation accuracy. Also, we prove that our proposed two schemes have the same minimum pilot overhead, which is as low as proportional to the product of the number of paths in the two MIMO channels (transmitter-RIS and RIS-receiver). Numerical results validate the effectiveness of our proposed methods.

Study on the influencing factors of combined processing of active and passive surface-wave data on dispersion imaging

Active and passive surface-wave methods have garnered significant attention in the near-surface geophysical community for their non-destructive, non-invasive, low-cost, and accurate advantages in delineating subsurface shear (S)-wave velocity structures. They are increasingly being utilized to address numerous engineering and environmental problems. Surface waves obtained from actively excited sources such as a hammer and a harmonic shaker, however, lack low-frequency components, resulting in limited investigation depth. Conversely, passive surface waves such as microseisms (< 0.4 Hz, associated with natural ocean wave activity) and microtremor (>1 Hz, generated by cultural and wind sources) retrieved from ambient seismic noise typically lack high-frequency components, which is not conductive to characterizing fine near-surface structures. To overcome these frequency limitations, we employ a “mixed-source data” strategy, imposing active shot gathers into ambient noise data, to widen the frequency range of dispersion images and depth of investigative capabilities. We simulate both active and passive surface-wave data based on a two-layer model, noting that their dispersion images suffer from a mode kissing phenomenon at lower frequencies. By analyzing influencing factors such as the amplitude intensity, the signal-to-noise ratio and the excitation locations of active shot gathers, as well as the length of passive surface-wave data, we better understand their impacts on dispersion images from mixed-source surface-wave data. Simulation tests demonstrate that processing mixed-source data can effectively distinguish the mode kissing phenomenon. Moreover, the effectiveness of this strategy in enhancing the quality of dispersion image is verified, especially when surface-wave dispersion images perform poorly in either the low- or high-frequency bands. Additionally, a real-world example further demonstrates that processing mixed-source data offers significant advantages in improving the quality of dispersion images. This way provides a convenient and efficient measurement strategy for delineating shear-wave velocity profiles in finer shallow layers and deeper penetration depths.

Nanomaterials as Next-Gen Corrosion Inhibitors: A Comprehensive Review for Ceramic Wastewater Treatment

This study reviews the use of corrosion inhibitors in industrial wastewater treatment, specifically in ceramic wastewater. It discusses the main problem limits the use of treated wastewater, which is corrosion behavior. To reduce this behavior and enable safe reuse of industrial wastewater, corrosion inhibitors are used. The study aims to provide insights into the selection, use, and effectiveness of corrosion inhibitor types in the media under study. The results can help engineers, researchers, and wastewater treatment professionals to find the best corrosion inhibitors for various municipal wastewater applications, increasing the sustainability and efficiency of wastewater treatment processes. The ceramic industry faces challenges in managing complex aqueous effluents generated from mining, shaping, glazing, and manufacturing processes. Nanomaterial-based alternatives, such as titanium nanotubes, zinc oxide nanoparticles, nanoenhanced filters, and stimuli responsive polymer and silica coatings, have emerged as promising next-generation corrosion inhibitors due to their multilayer passivation and high specific surface area. The analysis focuses on the feasibility of these materials' mechanisms, such as crystal deformation, nucleation hindrance, coating barriers, and passivation improvement, in industrial settings. In conclusion, the use of corrosion inhibitors in industrial wastewater treatment can significantly improve the sustainability and efficiency of wastewater treatment processes. Understanding the mechanisms by which these nanomaterials influence crystal growth modification, deposition kinetics, and passivation performance could lead to more effective and sustainable solutions for industrial wastewater treatment.

Controlling surface chemistry in cold sintering to advance battery materials

Cold sintering is a recently introduced densification method that is of interest due to the lower energy used in the process, the ability to densify metastable materials, the ability to integrate materials to develop unique composites, and the ability to synthesis materials that can be more easily recycled. Collectively, these advantages make cold sintering a promising approach for processing of battery components, and co-sintering into all solid-state batteries. To obtain high electrochemical performance with cold sintering, detailed control of the surface chemistry of powders is needed, to avoid or minimize the impact of carbonate formation in grain boundaries, and to limit concentrations of secondary phases that are a result of incongruent dissolution processes. In this paper, we outline the importance of surface chemical reactions of powders in cold sintering, and the mitigating processes that can be adopted to control these reactions and obtain high performance and unique opportunities for Li and Na-oxide secondary batteries. We focus on a series of examples that demonstrate how the control of low temperature densification (cold sintering) can address the environmental sensitivity of many battery materials, and highlight the issues faced and open questions. These examples include cold sintering of air-sensitive solid electrolytes, re-processing of crushed solid electrolytes, surface passivation of air-sensitive active materials for processing in air, and fabrication of solid-solid macroscopic interfaces for solid-state batteries.

Ligand Equilibrium Influences Photoluminescence Blinking in CsPbBr3: A Change Point Analysis of Widefield Imaging Data.

Photoluminescence intermittency remains one of the biggest challenges in realizing perovskite quantum dots (QDs) as scalable single photon emitters. We compare CsPbBr3 QDs capped with different ligands, lecithin, and a combination of oleic acid and oleylamine, to elucidate the role of surface chemistry on photoluminescence intermittency. We employ widefield photoluminescence microscopy to sample the blinking behavior of hundreds of QDs. Using change point analysis, we achieve the robust classification of blinking trajectories, and we analyze representative distributions from large numbers of QDs (Nlecithin = 1308, Noleicacid/oleylamine = 1317). We find that lecithin suppresses blinking in CsPbBr3 QDs compared with oleic acid/oleylamine. Under common experimental conditions, lecithin-capped QDs are 7.5 times more likely to be nonblinking and spend 2.5 times longer in their most emissive state, despite both QDs having nearly identical solution photoluminescence quantum yields. We measure photoluminescence as a function of dilution and show that the differences between lecithin and oleic acid/oleylamine capping emerge at low concentrations during preparation for single particle experiments. From experiment and first-principles calculations, we attribute the differences in lecithin and oleic acid/oleylamine performance to differences in their ligand binding equilibria. Consistent with our experimental data, density functional theory calculations suggest a stronger binding affinity of lecithin to the QD surface compared to oleic acid/oleylamine, implying a reduced likelihood of ligand desorption during dilution. These results suggest that using more tightly binding ligands is a necessity for surface passivation and, consequently, blinking reduction in perovskite QDs used for single particle and quantum light experiments.

Enhancing photoluminescence of WSe2 in vapor grown WSe2/VOCl bilayer heterojunctions via surface passivation.

Monolayer tungsten selenide (WSe2) has attracted attention due to its direct bandgap-generated strong light emission and light-matter interaction. Herein, vertical WSe2/VOCl bilayer heterojunctions with enhanced PL of WSe2 were synthesized by the vapor growth method. The morphology, crystal structure, and chemical composition of the WSe2/VOCl heterojunctions were systematically investigated, which confirmed the successful formation of the heterojunctions. The PL emission intensity of WSe2 obtained from the WSe2/VOCl heterojunction was about 2.4 times higher than that of the WSe2 monolayer, demonstrating the high optical quality of the WSe2/VOCl heterojunction, which was further confirmed by time-resolved PL measurements. The insulator top VOCl, which was deposited on the surface of the semiconductor bottom WSe2 as a surface passivation material, reducing the impurities and resulting in an atomically clean surface, successfully enhanced the PL emission of the bottom WSe2. This vertical WSe2/VOCl bilayer heterojunction with PL enhancement could provide a promising platform for optical devices.

Impact of crystallographic facet of InGaN micro-LED sidewalls on electro-optical characteristics

InGaN micro-LEDs (μLEDs) with their potential high-volume applications have attracted substantial research interest in the past years. In comparison to other III–V semiconductors, InGaN exhibits a reduced susceptibility toward non-radiative surface recombination. However, efficiency degradation becomes more prominent as dimensions shrink to a few μm or less. Due to the high surface-to-volume ratio of the miniaturized devices, the non-radiative recombination increases and reduces the internal quantum efficiency. While many groups focus on surface passivation to mitigate surface defects, the influence of crystallographic orientation of the μLED sidewall on the efficiency remains unexplored. This study addresses this gap by investigating the impact of crystallographic orientation of the sidewalls on the emission properties of the μLEDs. Hexagonal and elongated μLEDs with dimensions as small as 3.5 μm and sidewalls with crystallographically well-defined m- and a-planes were fabricated. Electrical and optical properties were investigated using photo- and electroluminescence. External quantum efficiency (EQE) is assessed based on well-known carrier recombination models. It can be shown that μLED performance intrinsically depends on the crystallographic orientation of the sidewalls. Comparing hexagonal μLED structures with a-plane and m-plane sidewalls, an increase in the EQE by 33% was observed for structures with a-plane sidewalls, accompanied by reduction in the current density of the peak EQE by a nearly two orders of magnitude compared to structures with m-plane sidewalls. By analyzing the EQE characteristics at the μLED center and near the sidewalls, the improvements can be directly attributed to the increased radiative recombination from sidewalls with a-plane orientation.

Interfacial engineering dominated passivation strategy to facilitate performance improvement of CsSnCl3 PSCs by induced Sn–O bonds: Insight from DFT calculations and device simulations

Defect passivation of perovskite surface not only reduces non-radiative recombination due to defect trapping charge, but also modulates the interfacial structure and energy levels, making it an effective means of solving the stability problem of perovskite materials. This work provides a passivation strategy for CsSnCl3 perovskite, and the interfacial interactions between CsSnCl3 and the passivation agent (PbSO4 and PbCO3) are explored based on first-principles density functional theory. By introducing PbSO4 and PbCO3 with multifunctional quantum dots, strong Sn-O bonds are formed with unsaturated coordination and dangling bonds on the surface of CsSnCl3. Binding sites of water molecules and impurities would be occupied by these bonds, to achieve surface passivation and dehumidification effects, and significantly improve the optical properties of CsSnCl3. PbCO3/SnCl and PbSO4/SnCl constructed the satisfactory interfacial energy level structures. PbCO3/SnCl exhibited excellent light absorption performance ranging in 0 ∼ 1200 nm. Introducing PbSO4 and PbCO3 reduced the refractive index of CsSnCl3 exhibiting excellent extinction properties. According to the simulation of Solar Design, perovskite solar cells (PSCs) constructed by (PbSO4, PbCO3)/CsSnCl3 as the active layer achieved power conversion efficiencies of 15.1946 % and 17.3783 %, respectively. This work’s research and design results provide a passivation strategy and PSCs design scheme for CsSnCl3 surface defects, which is of great significance for further modification of CsSnCl3 to better apply in photovoltaic field.

Two-dimensional perovskitoids enhance stability in perovskite solar cells.

Two-dimensional (2D) and three-dimensional (3D) perovskite heterostructures have played a key role in advancing the performance of perovskite solar cells1,2. However, the migration of cations between 2D and 3D layers results in the disruption of octahedral networks, leading to degradation in performance over time3,4. We hypothesized that perovskitoids, with robust organic-inorganic networks enabled by edge- and face-sharing, could impede ion migration. We explored a set of perovskitoids of varying dimensionality and found that cation migration within perovskitoid-perovskite heterostructures was suppressed compared with the 2D-3D perovskite case. Increasing the dimensionality of perovskitoids improves charge transport when they are interfaced with 3D perovskite surfaces-this is the result of enhanced octahedral connectivity and out-of-plane orientation. The 2D perovskitoid (A6BfP)8Pb7I22 (A6BfP: N-aminohexyl-benz[f]-phthalimide) provides efficient passivation of perovskite surfaces and enables uniform large-area perovskite films. Devices based on perovskitoid-perovskite heterostructures achieve a certified quasi-steady-state power conversion efficiency of 24.6% for centimetre-area perovskite solar cells. We removed the fragile hole transport layers and showed stable operation of the underlying perovskitoid-perovskite heterostructure at 85 °C for 1,250 h for encapsulated large-area devices in ambientair.

Enhanced ambient-stability and charge transport property of the CsPbBr3@Polyaniline

Although all-inorganic lead halide perovskites (CsPbX3 (X = Cl, Br, I)) have received widespread attention due to excellent optoelectronic properties, their low carrier mobility and poor stability have limited their application in photodetection. In this study, to alleviate these problems, CsPbBr3@Polyaniline composite is fabricated by passivating CsPbBr3 quantum dots (QDs) into a CSA-doped polyaniline conducting polymer. Notably, polyaniline is employed as a protective layer to block the structure damage of CsPbBr3 QDs against water, light and heat. The contact between polyaniline and CsPbBr3 QDs forms a type II heterojunction for charge transfer, which greatly reduces the recombination rate of charge carriers compared to pristine CsPbBr3 QDs. Benefiting from the high stability and enhanced charge mobility, CsPbBr3@Polyaniline-based photodetector achieves improved photocurrent signal and optical response time. The results demonstrate that the surface passivation could resolve the crucial stability problem and simultaneously facilitate the superior performance of perovskite optoelectronic devices.

Multishell Silver Indium Selenide-Based Quantum Dots and Their Poly(methyl methacrylate) Composites for Application in Red-Light-Emitting Diodes.

In this work, the production of novel multishell silver indium selenide quantum dots (QDs) shelled with zinc selenide and zinc sulfide through a multistep synthesis precisely designed to develop high-quality red-emitting QDs is explored. The formation of the multishell nanoheterostructure significantly improves the photoluminescence quantum yield of the nanocrystals from 3% observed for the silver indium selenide core to 27 and 46% after the deposition of the zinc selenide and zinc sulfide layers, respectively. Moreover, the incorporation of the multishelled QDs in a poly(methyl methacrylate) (PMMA) matrix via in situ radical polymerization is investigated, and the role of thiol ligand passivation is proven to be fundamental for the stabilization of the QDs during the polymerization step, preventing their decomposition and the relative luminescence quenching. In particular, the role of interface chemistry is investigated by considering both surface passivation by inorganic zinc chalcogenide layers, which allows us to improve the optical properties, and organic thiol ligand passivation, which is fundamental to ensuring the chemical stability of the nanocrystals during in situ radical polymerization. In this way, it is possible to produce silver-indium selenide QD-PMMA composites that exhibit bright red luminescence and high transparency, making them promising for potential applications in photonics. Finally, it is demonstrated that the new silver indium selenide QD-PMMA composites can serve as an efficient color conversion layer for the production of red light-emitting diodes.

Molecular cation and low-dimensional perovskite surface passivation in perovskite solar cells

Molecular cation and low-dimensional perovskite surface passivation in perovskite solar cells