Blend Layer Research Articles

Residual stress analysis on functionally graded 8% Y2O3-ZrO2 and NiCrAlY thermal barrier coatings

Thermal Barrier Coatings (TBCs) protect metallic components that operate in high temperature environments and enhance their service life. The conventional two-layered TBC system consists of a duplex ceramic top coat (TC) fabricated from 8 wt% yttria stabilized zirconia (8-YSZ) and an underlying bond coat (BC) comprised of intermetallic layers such as NiAl or MCrAlY (M = Co, Ni) etc. In the present study, functionally graded material (FGM) TBCs were fabricated by introducing a third blend layer of 8-YSZ and NiCrAlY, in between the BC and TC in order to enhance the thermal fatigue life of the TBC. The blend layer in FGM TBCs provides a smoother transition in thermal expansion properties between the metallic substrate and the top ceramic coat (8YSZ) which have widely different thermal expansion characteristics compared with each other. In service, thermal fatigue introduces severe tensile stresses between the coated layers and the substrates leading to ultimate detachment of the coatings from the substrates. In this work, residual stress analysis by Cos α method was carried out as a non-destructive assessment tool to foresee the likelihood of onset of failure in the TBCs, well before the damage was visible. The two-layered (conventional) and three-layered (FGM) TBCs were synthesized on Inconel 718 substrates by atmospheric plasma spray (APS) technique. The TBCs were subjected to thermal fatigue tests between 1200℃ (by using gas flame) and ambient temperature and evaluated for residual stress analysis at different stages of thermal fatigue testing. The goal was to assess if residual stress analysis could be used to determine if the TBC was about to fail well before the delamination occurred and the catastrophic failure could be avoided. The tests conducted and results obtained are presented.

Influence of Sidechain Elongation on Photovoltaic Response of Sidechain-Based Statistical Anthracene-Containing Copolymer

A new sidechain-based statistical anthracene-containing poly(arylene-ethynylene)-alt-poly(p-phenylene-vinylene) (P2) bearing 2-ethylhexyloxy and decyloxy side chains was synthesized to study the effect of elongating the sidechain length from octyloxy (as in P1) to decyloxy (as in P2) on the photovoltaic performance. The polymer was prepared using the Horner-Wadsworth-Emmons olefination reaction of two dialdehydes with two bisphosphonate esters. NMR and FTIR spectroscopy characterization were employed to prove the formation of the desired polymeric structure. The photophysical and electrochemical properties showed a broad spectral range of absorption in the visible region and reversible redox activity, respectively. Thermogravimetric analysis (TGA) indicated good thermal stability. Non-optimized bulk-heterojunction solar cells achieved power conversion efficiency (PCE) of 2.4 % for P2. The reduced performance of P2 compared to P1 based solar cells (PCE 3.8%) might originate from inferior nanomorphology of the active layer blend and/or the “dilution” of the photoactive conjugated backbone upon elongation of solubilising sidechains.

Structural Templating of an Organic Solar Cell Absorber by Ellagic Acid To Tune Its Aggregation, Molecular Orientation, and Optical Properties

Structural templating with homogeneous template layers is one of the strategies for controlling the orientation of small molecular absorbers in the photoactive layer of an organic solar cell to increase its power conversion efficiency. A main challenge thereby is the energetic alignment of the template molecules to the photoactive and charge-transporting materials. In the present study, the effects of a cluster-like template layer of ellagic acid (EA) on the morphology and optical properties of side-chain-substituted dicyanovinyl quaterthiophene (DCV4T-Et2) thin films are discussed. In the monolayer regime, J-aggregation of DCV4T-Et2 is confirmed. Insertion of the EA template layer leads to an improved aggregation behavior and formation of J-aggregates in DCV4T-Et2 films near the EA interface. The orientation of DCV4T-Et2 molecules in 30 nm thick films changes from “edge-on” to “face-on” due to a π–π interaction between the flat-lying EA molecules and the DCV4T-Et2 molecules. The face-on orientation by templating is preserved in blend layers with C60, and a considerable increase in the crystallinity of the DCV4T-Et2 phase in the blend is induced. Organic solar cells based on templated DCV4T-Et2:C60 active layers exhibit more than a 50% increase in the efficiency compared to nontemplated active layers. The short-circuit current density and the fill factor are significantly improved. Although the energetic alignment of EA is not ideal, no additional open-circuit voltage losses were observed with templating, due to the cluster-like morphology of the EA layer. Our results demonstrate a cluster-like templating approach with the novel template molecule EA to tailor the molecular orientation, crystallinity, and consequently optical properties of organic semiconducting molecules without significant energetic losses favorable for use in organic electronics.

Flexible Polymer-Organic Solar Cells Based on P3HT:PCBM Bulk Heterojunction Active Layer Constructed under Environmental Conditions.

In this study, some crucial parameters were determined of flexible polymer–organic solar cells prepared from an active layer blend of poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) mixed in 1:1 mass ratio and deposited from chlorobenzene solution by spin-coating on poly(ethylene terephthalate) (PET)/ITO substrates. Additionally, the positive effect of an electron transport layer (ETL) prepared from zinc oxide nanoparticles (ZnO np) on flexible photovoltaic elements’ performance and stability was investigated. Test devices with above normal architecture and silver back electrodes deposed by magnetron sputtering were constructed under environmental conditions. They were characterized by current-voltage (I–V) measurements, quantum efficiency, impedance spectroscopy, surface morphology, and time–degradation experiments. The control over morphology of active layer thin film was achieved by post-deposition thermal treatment at temperatures of 110–120 °C, which led to optimization of device morphology and electrical parameters. The impedance spectroscopy results of flexible photovoltaic elements were fitted using two R||CPE circuits in series. Polymer–organic solar cells prepared on plastic substrates showed comparable current–voltage characteristics and structural properties but need further device stability improvement according to traditionally constructed cells on glass substrates.

Bioactive Composite Nonwoven Surgical Dressing based on Cellulose Coated with Nanofiber Membrane using the layer-by-layer technique

Nonwoven fabric with cellulosic base has many Features ability to absorb biological fluids and can easily adapt for different types and locations of wounds, which made it common and unique in surgical dressing. The study aimed To design different samples made of one layer and two layers of nonwoven fabrics for the inner layer of deep endoscopic wound dressings to control the biological fluid leakage. 100% cotton, 100% viscose, and viscose/polyester (70:30) % were used as one layer samples, and every two different materials were used interchangeably to design the two-layer (layer-by-layer) samples. One-layer samples were dyed using green coffee extraction, while the two layers samples were enhanced by adding powdered green coffee between them, as an innovative use in the surgical dressing applications. Electrospinning technique was used to form a delicate membrane of Ciprofloxacin (CIP) antibiotic and Kylie Collagen to coat the single-layer samples without coffee dyeing to compare their performance with the dyed samples. Also, for comparing the results of the two layers samples that were enhanced with green coffee powder with and without the coating nanofibers membrane. Designed samples were evaluated by mechanical and physical properties for nonwoven fabrics, in addition, FTIR, SEM, absorbency and antimicrobial activity, and K/S especially for dyed samples, finally cytotoxicity for CIP, Kylie collagen, and green coffee. The results were pointed to that the dyed one-layer samples with green coffee extraction achieved a high-performance function for air permeability and antimicrobial activity. While the layer-by-layer samples that enhanced adding green coffee powder showed improvement for strength, absorbency properties, and antimicrobial activity, especially for the samples made of cotton/ viscose layers, and viscose/ viscose blended polyester layers, followed by the sample of cotton/ viscose blended polyester layers that were coated with 0.1wt% CIP antibiotic and Kylie Collagen membrane

Adjusting the Active Layer Morphology via an Amorphous Acceptor Solid Additive for Efficient and Stable Nonfullerene Organic Solar Cells

It is incredibly feasible and effective to adopt a solid additive strategy to optimize the active layer blend films morphology for nonfullerene organic solar cells (OSCs) to achieve high efficiency and stable performance. Herein, a novel amorphous small molecule SJ‐IC‐M with a comparatively high molecular weight is first designed and used as an efficient solid additive in the OSCs based on PM6:Y6 to enhance the power conversion efficiency (PCE) and long‐term stability of the device. After the addition of 0.5 wt% SJ‐IC‐M into the active layer blends, the PCE can be increased to 16.2% compared with that of the reference device without additive displaying an inferior PCE of 15.0%. Moreover, the device containing the SJ‐IC‐M additive delivers more excellent long‐term stability. The PCE can remain over 90% of its initial value when the unencapsulated device is preserved in a N2‐filled glovebox for a month. Systematic analysis reveals that the introduction of the relatively high molecular weight amorphous SJ‐IC‐M additive can optimize the crystallinity of Y6. As a result, an improved charge transport, stabilized blend morphology, and enhanced device performance are achieved. Moreover, the current research provides a new strategy which can replace the commonly used solvent additive to fabricate efficient and stable nonfullerene OSCs.

Enhancement Efficiency of Organic Photovoltaic Cells via Green Solvents and Nontoxic Halogen‐Free Additives

AbstractFor organic photovoltaic cells, the development of new green solvents and nontoxic and halogen‐free additives is an urgent issue. Here, a simple combination of o‐xylene (O‐XY) and ethyl 2‐hydroxybenzoate (EHB) is introduced in inverted devices based on poly[4,8‐bis(5‐(2‐ethylhexyl)‐thiophene‐2‐yl) benzo[1,2‐b;4,5‐b′] dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b] thiophene)‐2‐carboxylate‐2‐6‐diyl]:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PTB7‐Th:PC71BM) as blend layers, the device performance reaches optimal values (9.29%) when O‐XY and 3% EHB are introduced as additives, accompanied by the maximum fill factor (67.5%) and JSC (17.20 mA cm−2). From the results of characterization analysis, it is clear that EHB additive improves the crystallinity of the donor by regulating the kinetic process of active layer formation, selectively solubilizes the more aggregated fullerene acceptors, which allows PTB7‐Th to enter the conformational domain of PC71BM, and accelerates the molecular rearrangement. Besides, the EHB additive not only reduces the recombination, increases the carrier migration rate but also promotes the crystallinity of the donor, resulting in a tighter stacking. This work provides a green combination of solvents and additives that is important for the mass production of solar cells.

Coupling mechanism between photogenerated carriers and triboelectric charges and photoinduced reinforcement of a triboelectric nanogenerator

It has been reported that the output performance of a triboelectric nanogenerator (TENG) can be enhanced by applying light; however, the coupling mechanism between photogenerated carriers and triboelectric charges is still not well explained. Here, we propose a light-enhanced TENG based on a P3HT:PC61BM active blend layer, which processes dual functions of the photoelectric effect and the triboelectric effect. The open-circuit voltage, short circuit current, and amount of transferred charges for the TENG were enhanced by 63%, 76%, and 127%, respectively, after illumination under the white light condition. Moreover, we have investigated the interaction between the triboelectric charges and the photogenerated carriers to further explore the coupling mechanism between the triboelectric and photoelectric effects. Both Kelvin probe force microscopy and conductive atomic force microscopy demonstrate that the photogenerated carriers produced by the P3HT:PC61BM active blend layer can improve the surface triboelectric charge density. More interestingly, the transient absorption spectrum indicates that the electrostatic field induced by triboelectric charges contributes to the dissociation of excitons. In other words, there exists a beneficial promoting effect between the triboelectric charges and the photogenerated carriers during the operation of the light-enhanced TENG. This work provides an important guideline for the design and performance improvement of the hybrid TENG that captures both mechanical energy and light energy simultaneously.

Balanced Hole and Electron Transport in Ir(ppy)3:TCTA Blends

Balanced charge injection and transport in organic light-emitting diodes (OLEDs) is essential for highly efficient devices with small efficiency roll-off at high luminance. However, there are few reports on the measurement of charge mobility within the emissive blend layer of an OLED. In this paper, we show that photoexcitation in conjunction with Metal–Insulator–Semiconductor Charge Extraction with Linearly Increasing Voltage (photo-MIS-CELIV) can be used to determine the hole and electron mobilities of the emissive blend layer in a single device architecture. We demonstrate the technique by studying the commonly used emissive blend of fac-tris[2-phenylpyridinato-C2,N]iridium(III) [Ir(ppy)3] and tris(4-carbazoyl-9-ylphenyl)amine (TCTA), as well as neat TCTA and Ir(ppy)3 films. It was found that Ir(ppy)3 and its blend films with TCTA have measurable electron mobilities and critically they are of similar magnitude as their hole mobilities, irrespective of the Ir(ppy)3 doping ratio. Such balanced charge mobility suggests that the transport of both holes and electrons occurs mostly on the Ir(ppy)3 guest molecules in the blend. Additionally, we demonstrate that photo-MIS-CELIV can be used to measure the quantum efficiency of exciton dissociation in organic semiconductor thin films.

Analysis and optimization for vibration of laminated rectangular plates with blended layers

An accurate and straightforward analytical method is proposed for the free vibration of a laminated composite rectangular plate with blended layers. The plate with blended layers is defined here as a laminated plate where some of the outer layers are composed of multiple subareas with different orientation angles of straight fibers. A finite element code is developed as well to verify accuracy of the proposed method. In numerical comparison, the natural frequencies calculated by the present method agree well with those from the FEM code for rectangular plates with two, three, four and five subareas. Subsequently, the use of this analytical method is tested in vibration optimization, i.e. design for maximization of fundamental frequencies. This frequency optimization is formulated by changing the fiber orientation angles in multiple subareas simultaneously, and is carried out by using permutation in simple cases and by Genetic Algorithm (GA) for a larger number of frequency calculations. It is observed that introduction of blended layers is very effective approach to design the dynamic characteristics of laminated composite plates.

Diffusion in Organic Film Stacks Containing Solution-Processed Phosphorescent Poly(dendrimer) Dopants.

Efficient organic light-emitting diodes (OLEDs) consist of an emissive layer comprising a blend of a light-emitting and host material in contact with one or more charge transporting layers. The distribution of the active material in the guest-host emissive layer blend and the changes that may occur upon thermal annealing are two important factors in determining the stability and efficiency of OLEDs. We have combined neutron reflectometry and photoluminescence measurements to investigate the structures of films comprising an emissive layer containing a phosphorescent poly(dendrimer) material blended with 4,4'-N,N'-di(carbazolyl)biphenyl. This combination has been shown to give rise to highly efficient OLEDs. Here, we show that the emissive poly(dendrimer) material was not uniformly distributed in the host, but formed a concentration gradient within the emissive layer. Upon heating, the adjacent electron transport layer was found to intermix with the emissive layer, accompanied by changes in the material distribution in the emissive layer. The intermixing of the materials led to a decrease in the photoluminescence from the poly(dendrimer) within the film. The decrease in the photoluminescence was ascribed to an increase in interchromophore interactions that could arise from a conformational change of the poly(dendrimer) or phase separation leading to aggregation. The results indicate that, while uniform mixing of the guest and host is not essential for efficiency, the thermal stabilities of both host and charge transport materials are important for device durability.

Ternary Blend Organic Solar Cells Incorporating Ductile Conjugated Polymers with Conjugation Break Spacers

A broad family of ductile semirandom donor–acceptor (D–A) copolymers with 8-carbon alkyl conjugation break spacer (CBS) units were incorporated into ternary blend organic solar cells in order to determine their impact on the electrical metrics of solar cell performance. The goal of this study was to elucidate potential co-optimization strategies for photovoltaic and mechanical properties in organic solar cells. The ternary blended active layers were based on two polymer donors and the acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM). In all cases, the majority polymer donor component was the previously reported fully conjugated semirandom polymer P3HTT-ehDPP-10%, comprised of 80% 3-hexylthiophene, 10% diketopyrrolopyrrole (DPP) with 2-ethylhexyl (eh) side chains, and 10% thiophene. As the second donor, three different classes of CBS polymers were used, where the spacer length was kept constant at 8 methylene units. The mechanical properties of these polymers are quite notable with moduli as low as 8.54 MPa and fracture strains as high as 432%. However, it was found that as ductility increased, hole mobility decreased. In this study, we observed that the hole mobilities of the ternary active layers generally increased upon increasing the content of the CBS polymer up to 15% of the overall donor fraction. The higher carrier mobilities likely contribute to the higher JSC observed in many of the ternary devices. The as-cast ternary solar cells made in ambient environment without any pre/post treatment gave strong performance up to 25% of CBS polymer loading. This work demonstrates that introducing highly stretchable CBS polymers with poor charge mobility does not adversely affect solar cell performance, offering insights into the development of ternary strategies for flexible/stretchable organic solar cells.

Surface Pressure-Induced Interdiffused Structure Evidenced by Neutron Reflectometry in Cellulose Acetate/Polybutadiene Langmuir Films.

Binary blends of water-insoluble polymers are a versatile strategy to obtain nanostructured films at the air-water interface. However, there are few reported structural studies of such systems in the literature. Depending on the compatibility of the polymers and the role of the air-water interface, one can expect various morphologies. In that context, we probed Langmuir monolayers of cellulose acetate (CA), of deuterated and postoxidized polybutadiene (PBd) and three mixtures of CA/PBd at various concentrations by coupling surface pressure-area isotherms, Brewster angle microscopy (BAM), and neutron reflectometry at the air-water interface to determine their thermodynamic and structural properties. The homogeneity of the films in the vertical direction, averaged laterally over the spatial coherence length of the neutron beam (∼5 μm), was assessed by neutron reflectometry measurements using D2O/H2O subphases contrast-matched to the mixed films. At 5 mN/m, the whole mixed films can be described by a single slightly hydrated thin layer. However, at 15 mN/m, the fit of the reflectivity curves requires a two-layer model consisting of a CA/PBd blend layer in contact with the water, interdiffused with a PBd layer at the interface with air. At intermediate surface pressure (10 mN/m), the determined structure was between those obtained at 5 and 15 mN/m depending on film composition. This PBd enrichment at the air-film interface at high surface pressure, which leads to the PBd depletion in the blend monolayer at the water surface, is attributed to the hydrophobic character of this polymer compared with the predominantly hydrophilic CA.

High‐Efficiency Digital Inkjet‐Printed Non‐Fullerene Polymer Blends Using Non‐Halogenated Solvents

Inkjet printing (IJP) of polymer solar cells is ideal for small‐area off‐grid electronics with low power consumption. However, IJP is quite a complex technique compared with techniques such as spin coating or doctor blading. The IJP of polymer blends is reported based on ITIC derivatives as non‐fullerene acceptors (NFAs) using non‐halogenated solvents. The results show that fluorination of NFA is essential to form highly stable inks in o‐xylene, because ITIC has significantly insufficient solubility compared with ITIC‐4F. The importance of tetralin as a multifunctional co‐solvent for printing highly efficient PM6:ITIC‐4F blends is demonstrated, as even at very low concentrations, tetralin not only improves ink jettability and open nozzle time, but also improves drying behavior of the blend layer, resulting in blends with homogeneous micro‐ and nanoscale morphology. The resulting solar cells using inkjet‐printed polymer blends show a maximum efficiency of 10.1%. Moreover, IJP produces significant changes in the nanoscale and microscale morphology. In particular, the formation of a thin PM6 capping layer on the blend surface along with improved phase separation and crystallinity in both the donor and acceptor greatly reduces the recombination of charge carriers in thick blends, making inkjet‐printed photoactive films very promising for industrial applications.

Significantly Boosting Efficiency of Polymer Solar Cells by Employing a Nontoxic Halogen-Free Additive.

Traditional additives like 1,8-diiodooctane and 1-chloronaphthalene were successfully utilized morphology optimization of various polymer solar cells (PSCs) in an active layer, but their toxicity brought by halogen atoms limits their corresponding large-scale manufacturing. Herein, a new nontoxic halogen-free additive named benzyl benzoate (BB) was introduced into the classic PSCs (PTB7-Th:PC71BM), and an optimal power conversion efficiency (PCE) of 9.43% was realized, while there was a poor PCE for additive free devices (4.83%). It was shown that BB additives could inhibit PC71BM's overaggregation, which increased the interface contact area and formed a better penetration path of an active layer. In addition, BB additives could not only boost the distribution of a PTB7-Th donor at the surface, beneficial to suppressing exciton recombination in inverted devices but also boost the crystallinity of a blend layer, which is conducive to exciton dissociation and charge transport. Our work effectively improved a device performance by using a halogen-free additive, which can be referential for industrialization.

High-Performance Organic Photovoltaics Incorporating an Active Layer with a Few Nanometer-Thick Third-Component Layer on a Binary Blend Layer.

In this paper, a universal approach toward constructing a new bilayer device architecture, a few-nanometer-thick third-component layer on a bulk-heterojunction (BHJ) binary blend layer, has been demonstrated in two different state-of-the-art organic photovoltaic (OPV) systems. Through a careful selection of a third component, the power conversion efficiency (PCE) of the device based on PM6/Y6/layered PTQ10 layered third-component structure was 16.8%, being higher than those of corresponding devices incorporating the PM6/Y6/PTQ10 BHJ ternary blend (16.1%) and the PM6/Y6 BHJ binary blend (15.5%). Also, the device featuring PM7/Y1-4F/layered PTQ10 layered third-component structure gave a PCE of 15.2%, which is higher than the PCEs of the devices incorporating the PM7/Y1-4F/PTQ10 BHJ ternary blend and the PM7/Y1-4F BHJ binary blend (14.2 and 14.0%, respectively). These enhancements in PCE based on layered third-component structure can be attributed to improvements in the charge separation and charge collection abilities. This simple concept of the layered third-component structure appears to have great promise for achieving high-performance OPVs.

The Effect of Shallow Trap Density on the Electrical Characteristics of an Organic Nonvolatile Memory Device Based on Eight-Hydroxyquinoline

An organic nonvolatile memory is proposed based on the synergistic effect of the (three-aminopropyl) triethoxysilane (APTES) self-assembled monolayer (SAM) and the polystyrene (PS):eight-hydroxyquinoline (8-HQ) blend layer, where 8-HQ is used to provide the trapping sites for the nonvolatile memory, and PS is used to form the matrix for 8-HQ in order to improve the memory property. In addition, the introduced APTES SAM aims to further increase the memory window. Two kinds of PS:8-HQ blend films are adopted, with lower 8-HQ concentration of 50 mg/mL and high spin-coating speed of 5000 rpm to form smooth thin film, while with high 8-HQ concentration of 100 mg/mL and low spin-coating speed of 1000 rpm to form rough thick film. The roughness and the surface modification property of the PS:8-HQ blend film greatly affect the morphology of the active layer, and thus the shallow trap density is also influenced, which further affects the electrical characteristics and memory properties of the nonvolatile memory device. The better characteristics of the memory device with thin 8-HQ layer indicate the potential applications in many domains.

Cyclometalated Ir(III) complexes as potential electron acceptors for organic solar cells.

Cyclometalated iridium(iii) complexes have been investigated as promising electron donor (D) materials in organic solar cells (OSCs) due to their unique octahedral configuration for optimized morphology and their significantly long lifetimes potentially for enhanced exciton dissociation. However, the application as electron acceptor (A) materials has never been reported. In order to fill this blank, herein, two cyclometalated heteroleptic Ir complexes, TRIr and 2TRIr, based on electron donating-accepting type organic ligands with different π-conjugation lengths are reported as electron acceptor materials in comparison with their corresponding main organic ligands. The two Ir complexes exhibit suitable HOMO/LUMO energy levels of -5.55/-3.47 eV and -5.44/-3.48 eV, which are ∼0.1 eV higher in the HOMO and ∼0.15 eV deeper in the LUMO than the TR and 2TR ligands, respectively. 2TRIr with extended ligand π-conjugation displays a poor triplet feature, while TRIr demonstrates obvious metal-to-ligand charge transfer (MLCT) transition absorption, with a triplet component photoluminescence (PL) lifetime of 85 ns in neat films. When blended with PBDB-T in bulk heterojunction (BHJ) OSCs, the power conversion efficiencies (PCEs) are 2-3 times higher than their relevant ligands, with values of 1.20% and 1.62% for TRIr and 2TRIr, and 0.58% and 0.47% for the TR and 2TR ligand-based devices, respectively. TRIr and 2TRIr based active layer blends exhibit poorer hole and electron mobilities, whereas compared with their relatively linear planar ligands, both of the two octahedral Ir complexes exhibit an optimized surface morphology for less bimolecular recombination and more efficient exciton dissociation, thus contributing to improved photovoltaic performance.

Fascial Plane Blocks: More Questions Than Answers?

Fascial Plane Blocks: More Questions Than Answers?

Influence of the PVOH molar mass on the morphology and functional properties of EVOH/PVOH films prepared by melt blending

AbstractThe influences of the molar mass (low, medium, and high) and content of poly(vinyl alcohol) (PVOH) dispersed by melt‐blending in an ethylene vinyl alcohol (EVOH) copolymer on the morphology, microstructure, thermal, mechanical, and oxygen barrier properties were investigated. Multilayer films with external low‐density polyethylene layers and inner EVOH/PVOH blend layer and respective monolayer films were elaborated and characterized. EVOH/PVOH blends exhibited a good compatibility because of the initial presence of PVOH segments in EVOH. The detailed quantitative analysis of the morphology performed for all blends showed that the finest dispersion was obtained with the PVOH with the lowest molar mass. The properties of the films as a function of the PVOH content and its molar mass were determined herein. Significant improvement of barrier properties was obtained at moderated water activities (up to aw = 0.6) by using the PVOH with the lowest molar mass. Compared to the neat EVOH material, the oxygen permeability coefficients decreased by a factor 2 by adding 15 vol% PVOH while the thermal and mechanical properties remained similar.