Tri Layer Research Articles

ZnO-based inverted organic solar cells: a comparative analysis of simulation and experimental devices

ZnO-based Inverted Organic Solar Cells (OSCs) were simulated using the Solar Cell Capacitance Simulator (SCAPS-1D) software. Two different device architectures were employed: single-layer (SL) and trilayer (TL) configurations. In the SL-OSCs, the structure consisted of a P3HT/PCBM blend between ZnO and molybdenum oxide (MoO3) layers. The P3HT/PCBM blend layers were combined with thin layers from donor (P3HT) and acceptor (PCBM) materials for the TL-OSCs. Electrospray deposition (ESD) was utilized to fabricate the OSCs for comparison. The analysis of the results showed that the TL-OSCs exhibited improved device performance and operational stability compared to the SL devices. Simulated efficiencies were 2.85% for TL and 2.25% for SL, whereas experimental OSCs yielded 1.47% (TL) and 0.84% (SL) efficiencies. This increasing trend in TL-OSCs’ performance aligns with existing literature. Furthermore, the TL OSC structures demonstrated good stability at optimum annealing temperatures up to 130 °C. Additionally, the ZnO-based TL devices displayed enhanced ambient stability under continuous 8h illumination compared to SL-OSCs. This improvement can be attributed to the interfacial layer, which aids in separating charge carriers and reducing recombination rates, consequently enhancing overall device efficiency. The stacked layers in TL OSCs may also function as a barrier, inhibiting diffusion and protecting against moisture and oxygen exposure, thereby contributing to improved device stability.

Interplay between magnetic order and electronic band structure in ultrathin GdGe2 metalloxene films.

Dimensionality can strongly influence the magnetic structure of solid systems. Here, we predict theoretically and confirm experimentally that the antiferromagnetic (AFM) ground state of bulk gadolinium germanide metalloxene, which has a quasi-layered defective GdGe2 structure, is preserved in the ultrathin film limit. Ab initio calculations demonstrate that ultrathin GdGe2 films present in-plane intra-layer ferromagnetic coupling and AFM inter-layer coupling in the ground state. Angle-resolved photoemission spectroscopy finds the AFM-induced band splitting expected for the 2 and 3 GdGe2 trilayer (TL) films, which disappear above the Néel temperature. The comparative analysis of isostructural ultrathin DyGe2 and GdSi2 films confirms the magnetic origin of the observed band splitting. These findings are in contrast with the recent report of ferromagnetism in ultrathin metalloxene films, which we ascribe to the presence of uncompensated magnetic moments.

Band-gap engineering and optoelectronic properties of 2D WSi2N4 nanosheets: A first principle calculations

The successful growth of centimeter-scale monolayer films of MoSi 2 N 4 and WSi 2 N 4 has attracted great interest (Science 369, 670, 2020). Here, we systematically investigate the effects of biaxial and uniaxial strain on the electronic structures of WSi 2 N 4 nanosheets with different layers of monolayer(ML), bilayer(BL) and trilayer(TL), respectively, by using first-principles calculations. In addition, combined with the non-equilibrium Green’s function methods, the photoelectronic response of WSi 2 N 4 ML is also explored. The results indicate that: 1) The biaxial and uniaxial strain can flexibly increase or decrease the band gap of WSi 2 N 4 nanosheets. Particularly, tensile strain realizes the transition of WSi 2 N 4 nanosheets from semiconductor to metal. 2) The tensile strain effectively improves the optical properties of WSi 2 N 4 nanosheets in the visible light region, and the red/blue shift of the absorption peaks is observed in the optical spectrum by tensile/compressive strain. 3) The pin-junction photodiode of WSi 2 N 4 ML generates sizable photocurrents under illumination, showing a strong photoelectronic response to purple light. Furthermore, the biaxial tensile strain significantly enhances the photoelectric performance of the WSi 2 N 4 photodiode and effectively modulates its detection range in the visible region. Hence, our findings suggest that WSi 2 N 4 nanosheets are a promising multifunctional material for nanoelectronic and optoelectronic applications. • Electronic structure and optoelectronic properties studies of the 2D WSi 2 N 4 nanosheets. • Strain engineering can effectively modulate the band gap and optical properties of WSi 2 N 4 nanosheets. • The pristine WSi 2 N 4 monolayer is predicted to be a good photoelectric sensor, showing a strong photoelectronic response to purple light. • The tensile strain significantly enhance the photoelectric performance of the WSi 2 N 4 photodiode and effectively modulates its detection range in the visible region.

Masking Ability of Monolithic and Layered Zirconia Crowns on Discolored Substrates.

There is scarce information on the colorimetric behavior of monolithic and layered zirconia crowns in combination with various abutment colors. This study evaluated the masking ability on discolored substrates of monolithic and layered zirconia crowns. Anterior crowns were fabricated using 3Y-TZP zirconia and layering ceramic and divided into three groups: monolithic (ML), bi-layer (BL), and tri-layer (TL). The crowns were placed over eleven substrates (ND1-ND9, zirconia, metal), and CIE L*, a*, b*, C*, and h° color coordinates were measured in the cervical, middle, and incisal areas with a spectrophotometer. Masking ability was calculated using the color difference formula, and values were interpreted according to the perceptibility and acceptability thresholds. Data were analyzed statistically (α = 0.001). The L* coordinate was not significantly different between BL and TL crowns, regardless of the measurement area or substrate (p ≥ 0.001). In the middle area, the L* coordinate of the ML group was statistically different from the BL and TL groups only for zirconia and metal substrates, while in the incisal area, only for ND7 and metal substrates. The a* coordinate was significantly different between the ML and layered crowns for all measurement areas and substrates (except zirconia). The b* and C* coordinates differed significantly between the groups only in the cervical area (p < 0.001). The ML crown had better masking ability than the BL and TL crowns. However, the color differences for ML crowns were below the acceptability threshold for ND2, ND3, and ND7 substrates in the cervical and middle areas and below perceptibility threshold only for the incisal area. The lowest masking ability of the crowns was found for ND9 and metal substrates in all measurement areas.

Soft X-Ray Spectroscopy of Low-Valence Nickelates

Low-valence nickelates—including infinite-layer (IL) and trilayer (TL) compounds—are longstanding candidates for mimicking the high-temperature superconductivity of cuprates. A recent breakthrough in the field came with the discovery of superconductivity in hole-doped IL nickelates. Yet, the degree of similarity between low-valence nickelates and cuprates is the subject of a profound debate for which soft x-ray spectroscopy experiments at the Ni L- and O K-edge provided critical input. In this review, we will discuss the essential elements of the electronic structure of low-valance nickelates revealed by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). Furthermore, we will review magnetic excitations observed in the RIXS spectra of IL and TL nickelates, which exhibit characteristics that are partly reminiscent of those of cuprates.

Facile deposition of environmentally benign organic-inorganic flame retardant coatings to protect flammable foam

The combination of clay and intumescent, also termed hybrid organic−inorganic coating is an attractive strategy to improve the flame retardancy of polyurethane foam (PUF). However, the fabrication of such flame retardants remains challenging as it requires the deposition of many layers to achieve the desired level of the intumescing effect. Herein, we describe a facile route to fabricate a hybrid clay−intumescent coating comprising a OnePot−deposited chitosan (CH)−phytic acid (PA) polyelectrolyte complex (PEC) intumescent stacked on top of a layer-by−layer self−assembled clay trilayer (TL) of poly−d −lysine, CH, and alginate-stabilized montmorillonite. Combustibility tests using cone calorimetry revealed that a PUF coating of CH−PA PEC intumescent on a 5 TL clay nanobrick wall (CH−PA@5 TL@PUF) can reduce the peak heat release rate (a critical flammability metric), peak rate of smoke release, and peak CO2 production rate of neat PUF by 73%, 33%, and 65%, respectively. Additionally, this hybrid coating imparted UL−94 horizontal burning rating by avoiding melt dripping and flashover, while the neat foam was completely consumed during the UL−94 flammabilty test. The proposed method is adaptable for the facile construction of other multifunctional surfaces in various application fields.

Strong bulk photovoltaic effect and second-harmonic generation in two-dimensional selenium and tellurium

Few-layer selenium and tellurium films have been recently prepared, and they provide a new platform to explore novel properties of two-dimensional (2D) elemental materials. In this work, we have performed a systematic first-principles study on the electronic, linear, and nonlinear optical (NLO) properties of atomically thin selenium and tellurium films within the density-functional theory with the generalized gradient approximation plus scissors correction using the band gaps from the relativistic hybrid Heyd-Scuseria-Ernzerhof functional calculations. Interestingly, we find that few-layer Se and Te possess large second-harmonic generation (SHG), linear electro-optic effect, and bulk photovoltaic effect. In particular, trilayer (TL) Te possesses large SHG coefficient, being more than 65 times larger than that of GaN, a widely used NLO material. Bilayer (BL) Te has huge static SHG coefficient, being more than 100 times larger than that of GaN. Furthermore, monolayer (ML) Se possesses large SHG coefficient. Moreover, we predict that TL Te exhibits strong bulk photovoltaic effect (BPVE), being greater than that of GeS, a polar system with the largest BPVE found so far. Although the shift current conductivities of bulk and 2D Se are comparable, the shift current conductivities of TL Te are five times larger than those of bulk Te. Finally, an analysis of the calculated electronic band structures indicates that the strong NLO responses of 2D Se and Te materials are primarily derived from their low-dimensional structures with high anisotropy, directional covalent bonding, lone-pair electrons, and relatively small band gaps. These findings provide a practical strategy to search for excellent NLO and BPVE materials.

Large magneto-optical effects and magnetic anisotropy energy in two-dimensional Cr2Ge2Te6

By performing systematic $ab$ $initio$ density functional calculations, here we study two relativity-induced properties of atomically thin ferromagnetic (FM) Cr$_2$Ge$_2$Te$_6$ films [monolayer (ML), bilayer (BL) and trilayer (TL) as well as bulk], namely, magnetic anisotropy energy (MAE) and magneto-optical (MO) effects. Competing contributions of both magneto-crystalline anisotropy energy (C-MAE) and magnetic dipolar anisotropy energy (D-MAE) to the MAE, are computed. Calculated MAEs of these materials are large, being in the order of $\sim$0.1 meV/Cr. Interestingly, we find that the out-of-plane magnetic anisotropy is preferred in all the systems except the ML where an in-plane magnetization is favored because here the D-MAE is larger than the C-MAE. Crucially, this explains why long-range FM order was observed in all the few-layer Cr$_2$Ge$_2$Te$_6$ except the ML because the out-of-plane magnetic anisotropy would open a spin-wave gap and thus suppress magnetic fluctuations so that long-range FM order could be stabilized at finite temperature. In the visible frequency range, large Kerr rotations up to $\sim$1.0 deg in these materials are predicted and they are comparable to that observed in famous MO materials such as PtMnSb and Y$_3$Fe$_5$O$_{12}$. Moreover, they are $\sim$100 times larger than that of 3$d$ transition metal MLs deposited on Au surfaces. Faraday rotation angles in these 2D materials are also large, being up to $\sim$120 deg/$\mu$m, and are thus comparable to the best-known MO semiconductor Bi$_3$Fe$_5$O$_{12}$. These findings thus suggest that with large MAE and MO effects, atomically thin Cr$_2$Ge$_2$Te$_6$ films would have potential applications in novel magnetic, MO and spintronic nanodevices.

Formation of Trilayer Ices in Graphene Nanocapillaries under High Lateral Pressure

Using molecular dynamics simulation, we investigate the phase behavior of water confined in graphene nanocapillaries at room temperature (300 K). Here, the lateral pressure Pzz is used as the primary controlling variable, and its effect on the behavior of trilayer water is systematically studied. Three (meta)stable trilayer (TL) crystalline/amorphous ice phases, namely, TL-ABAI, TL-ABA, and TL-AAAI, are observed in our simulations with the lateral pressure in the range of 1.0 GPa ≤ Pzz ≤ 6.0 GPa. TL-ABAI exhibits a square lattice in every layer, and the three layers exhibit the ABA stacking pattern; i.e., the oxygen atoms in the two outer layers are in registry. This new trilayer ice structure can also be viewed as a bilayer clathrate hydrate with water molecules in the middle layer serving as the guest molecules. With increasing lateral pressure, typically, the solid-to-liquid-to-solid phase transition occurs, during which the structural transformation from triangular to square-like in the ice layer is accompanied by a sudden jump in P⊥ (normal pressure) and in potential energy (per molecule). The oxygen density profiles of the three trilayer structures show a common feature; that is, the peak of the middle layer is markedly lower than that of the two outer layers. The computed diffusivity suggests that water in the middle layer exhibits behavior different from that in the two outer layers in contact with the graphene. For TL-AAAI, the diffusion of water molecules in the layer next to the graphene is faster than that in the middle layer.

Theoretical study of thermoelectric properties of few-layer MoS2 and WSe2

Molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) are prototypical layered two-dimensional transition metal dichalcogenide materials, with each layer consisting of three atomic planes. We refer to each layer as a trilayer (TL). We study the thermoelectric properties of 1-4TL MoS2 and WSe2 using a ballistic transport approach based on the electronic band structures and phonon dispersions obtained from first-principles calculations. Our results show that the thickness dependence of the thermoelectric properties is different under n-type and p-type doping conditions. Defining ZT1st peak as the first peak in the thermoelectric figure of merit ZT as doping levels increase from zero at 300 K, we found that ZT1st peak decreases as the number of layers increases for MoS2, with the exception of 2TL in n-type doping, which has a slightly higher value than 1TL. However, for WSe2, 2TL has the largest ZT1st peak in both n-type and p-type doping, with a ZT1st peak value larger than 1 for n-type WSe2. At high temperatures (T > 300 K), ZT1st peak dramatically increases when the temperature increases, especially for n-type doping. The ZT1st peak of n-type 1TL-MoS2 and 2TL-WSe2 can reach 1.6 and 2.1, respectively.

Multi-walled carbon nanotube layer-by-layer coatings with a trilayer structure to reduce foam flammability

In order to improve the stability and growth speed of coating, a trilayer (TL) methodology was adapted and resulting film shows high thickness compared to the dimensions of the carbon nanotube. First, the multi-walled carbon nanotubes were functionalized via simple direct amination to be stabilized in the water with positive surface charge. Amine functionalized carbon nanotubes were deposited on polyurethane foam using layer-by-layer assembly with a TL approach. Additional polyethyleneimine layer promote the interaction between carbon nanotube and polymer layers resulting in uniform, durable and thick coating. The 440±47nm thick 4 TL coatings of polyacrylic acid, polyethyleneimine functionalized multi-walled carbon nanotubes, and polyethyleneimine completely covers the entire internal and external surfaces of the foam. Microscopic images confirm strong polymer/nanotube interaction due to additional polyethyleneimine layer and well dispersed carbon nanotube network on the polyurethane foam surface. The carbon nanotube network created by the layer-by-layer process significantly reduces the flammability of foam (e.g., 35±3%) reduction in peak heat release rate and prevents pool fire by creating protective layer.

Phosphorous-filled nanobrick wall multilayer thin film eliminates polyurethane melt dripping and reduces heat release associated with fire

Abstract Unique trilayer (TL) thin films of sodium montmorillonite (MMT), poly(allylamine hydrochloride) (PAH) and poly(sodium phosphate) (PSP) are prepared via layer-by-layer (LbL) assembly. This three-component nanocoating completely shuts down melt dripping and reduces heat release of open-celled flexible polyurethane (PU) foam when exposed to direct flame due to a synergistic interaction between PSP and the thermally shielding clay platelets in the condensed phase. Post burn scanning electron microscopy reveals the nanocoating's swollen morphology is able to maintain foam shape, cellular structure, and porosity. Cone calorimetry reveals that 4 TL coated foams (

Controlling polyurethane foam flammability and mechanical behaviour by tailoring the composition of clay-based multilayer nanocoatings

This study is a thorough evaluation of clay-based Layer-by-Layer (LbL) coatings intended to reduce the flammability of polymeric materials. Through a systematic variation of a baseline coating recipe, an ideal combination of the coating attributes that provides a rapidly developing coating with an optimum balance of flammability, mechanical, and physical attributes on a complex 3D porous substrate, polyurethane foam (PUF) was identified. Using a unique trilayer (TL) assembly approach, the coating growth was significantly accelerated by the polymer (poly(acrylic acid) (PAA)/branched polyethylenimine (BPEI)) concentration in the formulation. However, to significantly reduce flammability without compromising other performance attributes, the concentration of the nanoparticle fire retardant (nanoFR, clay) suspension was critical. This study has resulted in the most significant reduction in PUF flammability using LbL technology without compromising any of the mechanical or physical attributes of the PUF. More specifically, a reduction in the peak heat release rate (pHRR) and average heat release rate (aHRR) of 33% and 78%, respectively, has been achieved. This reduction in flammability is at least two times more effective than commercial fire retardants and other LbL FR coatings for PUF. The insights gained through this research are expected to accelerate the development of other LbL coatings regardless of the intended application.