Blend Films Research Articles

Laser deposited ultra-thin silver nanoparticles on CMC-PVA blend film as sheet for wound dressings

In this study, silver nanoparticles (AgNPs) were synthesized using pulsed laser deposition and deposited on a sheet film composed of Carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and AgNPs. These polymeric-based nano-composites were investigated for their potential application in wound healing. The structural properties of the composites were examined using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). Morphological features were observed through field emission scanning electron microscopy (FESEM), and roughness characteristics were studied using FESEM micrographs. The CMC-PVA-AgNPs scaffolds with deposition times of 10 and 12.5 min showed minimal deviations in surface structure compared to the composites with longer deposition times, where scattered AgNPs and aggregates were observed. Furthermore, the roughness parameter (Ra) values indicated the potential of silver NPs in creating trapping sites and crystal defects, as evidenced by an increase in Ra from 18.96 nm in the pure CMC-PVA blend to 34.17 nm at a deposition time of 20 min. The optical properties of the composites were investigated by determining the band-gap of direct and indirect transition modes, which exhibited a decreasing trend. The presence of silver NPs was confirmed by the plasmon absorption band observed around 400 nm. The intensity of the plasmon peaks increased with longer laser deposition times, indicating an increase in the silver content over time. Finally, the antibacterial activity of the prepared scaffolds against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Micrococcusluteus was evaluated, and the results strongly support the potential of the prepared material for biological applications. In conclusion, the synthesized CMC-PVA-AgNPs nano-composites deposited using pulsed laser deposition technique exhibited promising properties for wound healing applications. The comprehensive characterization of the composites, including their structural, morphological, optical, and antibacterial properties, provides valuable insights for further research and development in the field of biomaterials.

Epitaxial Growth of Surface Perforations on Parallel Cylinders in Terraced Films of Block Copolymer/Homopolymer Blends.

Due to incommensurability between initial thickness and interdomain distance, thermal annealing inevitably produces relief surface terraces (islands and holes) of various morphologies in thin films of block copolymers. We have demonstrated three kinds of surface terraces in blend films: polygrain terraces with diffuse edges, polygrain terraces with step edges, and pseudo-monograin terraces with island coarsening. The three morphologies were obtained by three different thermal histories, respectively. The thermal histories were imposed on blend films, which were prepared by mixing a homopolystyrene (hPS, 6.1 kg/mol) with a weakly segregated, symmetry polystyrene-block poly(methyl methacrylate) (PS-b-PMMA, 42 kg/mol) followed by spin coating. At a given weight-fraction ratio of PS-b-PMMA/hPS = 75/25, the interior of the blend films forms parallel cylinders. Nevertheless, the surface of the blend films is always dominated by a skin layer of perforations, which epitaxially grow on top of parallel cylinders. By oxygen plasma etching at various time intervals to probe interior nanodomains, the epitaxial relationship between surface perforations and parallel cylinders has been identified by a scanning electron microscope.

Polymerizing M-Series Acceptors for Efficient Polymer Solar Cells: Effect of the Molecular Shape.

Currently, high-performance polymerized small-molecule acceptors (PSMAs) based on ADA-type SMAs are still rare and greatly demanded for polymer solar cells (PSCs). Herein, two novel regioregular PSMAs (PW-Se and PS-Se) are designed and synthesized by using centrosymmetric (linear-shaped) and axisymmetric (banana-shaped) ADA-type SMAs as the main building blocks, respectively. It is demonstrated that photovoltaic performance of the PSMAs can be significantly improved by optimizing the configuration of ADA-type SMAs. Compared to the axisymmetric SMA-based polymer (PS-Se), PW-Se using a centrosymmetric SMA as the main building block exhibits better backbone coplanarity thereby resulting in bathochromically shifted absorption with a higher absorption coefficient, tighter interchain π-π stacking, and more favorable blend film morphology. As a result, enhanced and more-balanced charge transport, better exciton dissociation, and reduced charge recombination are achieved for PW-Se-based devices with PM6 as polymer donor. Benefiting from these positive factors, the optimal PM6:PW-Se-based device exhibits a higher power conversion efficiency (PCE) of 15.65% compared to the PM6:PS-Se-based device (8.90%). Furthermore, incorporation of PW-Se as a third component in the binary active layer of PM6:M36 yields ternary devices with an outstanding PCE of 18.0%, which is the highest value for PSCs based on ADA-type SMAs, to the best of the knowledge.

High-performance intrinsically stretchable organic solar cells based on flexible spacer incorporated dimerized small-molecule acceptors

High power conversion efficiency (PCE), long-term stability, and mechanical robustness are important requirements for the practical applications of organic solar cells (OSCs). Herein, we develop a series of flexible spacer (FS)-incorporated dimerized small-molecule acceptors (DSMAs; DYBT-C0, DYBT-C4, and DYBT-C8) and demonstrate high-performance OSCs with a high PCE of 18.6%, excellent mechanical robustness (crack-onset strain (COS) = 32%) and photostability (t80% lifetime = 1735 h under 1-sun illumination). The incorporation of aliphatic FS units with optimal length effectively reduces the backbone rigidity of the DSMAs and increases the fraction of intermixed domains in the blend films, while maintaining excellent electron transport properties. The DYBT-C4-based OSCs demonstrate higher PCE (18.6%) and stretchability (COS = 32%) compared to the OSCs based on the monomer acceptor (MYT; PCE = 15.9% and COS = 10%) and DSMA without FS units (DYBT-C0; PCE =17.2% and COS = 17%). In addition, due to the reduced diffusion coefficient and higher glass transition temperature of DYBT-C4, the DYBT-C4-based OSCs exhibit photostability significantly higher than that of the OSCs fabricated using MYT (t80% lifetime= 36 h). Consequently, DYBT-C4-based intrinsically stretchable (IS)-OSCs exhibit high device stretchability (strain at PCE80% = 36%) and PCE of 14.3%, demonstrating potential for wearable applications.

Synergetic optimizing quinoxaline and selenophene substitution in non-fullerene acceptors for efficient organic solar cells

Selenophene-fused non-fullerene acceptors (Se-NFAs) usually exhibited improved short circuit current density (JSC) in organic solar cells, while acceptors bearing quinoxaline (Qx) unit as the central core could achieve enhanced open circuit voltage (VOC). Herein, we incorporated the advantages of the above two strategies and synthesized four nonfullerene acceptors (Qx-Se-NFAs), including Qx-Se-F, Qx-Se-Cl, p-2FQx-Se-F, and p-2FQx-Se-Cl. Compared with CH1007 (the symmetrical selenium analog of Y6), the four acceptors-based devices showed evidently improved VOC and fill factor (FF) with well-maintained JSC, achieving excellent power conversion efficiency (PCE). Qx-Se-NFAs-based devices with the fluorinated terminal group exhibit evidently advantages on VOC and FF compared with the chlorinated terminal group due to the up-shifted LUMO energy level and optimized blend film. In addition, the acceptors with fluorination on the central core could further endow device with improved carrier properties and film morphology. Consequently, the device based on Qx-Se-F exhibited the highest VOC of 0.867 V among the reported PM6:Se-NFA systems. The p-2FQx-Se-F-based device yielded a champion PCE of 18.67% by using 2PACz as the hole transport layer, which is the highest PCE in the reported Se-NFAs among the single-junction binary OSCs. This work demonstrated a promising strategy that could better trade-off JSC, FF, and VOC in Se-NFAs.

Molecular Design of Fully Nonfused Acceptors for Efficient Organic Photovoltaic Cells.

The nonfused thiophene-benzene-thiophene (TBT) unit offers advantages in obtaining low-cost organic photovoltaic (OPV) materials due to its simple structure. However, OPV cells, including TBT-based acceptors, exhibit significantly lower energy conversion efficiencies. Here, we introduce a novel approach involving the design and synthesis of three TBT-based acceptors by substituting different position-branched side chains on the TBT unit. In comparison to TBT-10 and TBT-11, TBT-13, which exclusively incorporates α-position branched side chains with a large steric hindrance, demonstrates a more planar and stable conformation. When blended with the donor PBQx-TF, TBT-13-based blend film achieves favorable π-π stacking and aggregation characteristics, resulting in excellent charge transfer performance in the corresponding device. Due to the simultaneous enhancements in short-circuit current density and fill factor, the TBT-13-based OPV cell obtains an outstanding efficiency of 16.1%, marking the highest value for the cells based on fully nonfused acceptors. Our work provides a practical molecular design strategy for high-performance and low-cost OPV materials.

Effects of different biopolymers and additives on mechanical and barrier properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) blend films

Bio-based materials could offer solutions to the problems of petroleum-derived material usage and waste management. By taking into consideration this fact, the aim of this study was to create alternative product recipes for flexible packaging with the use of biodegradable polymers in line with sustainable packaging targets. In this study, the exit point was to prepare polybutylene adipate terephthalate (PBAT) and polyhydroxyalkanoate (PHA)-based bioblends with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by solution casting method in order to create biocomposite combination for flexible packaging with improved properties. Hydroxypropyl methylcellulose (HPMC) additive was used to enhance barrier properties. Thermal, mechanical, optical properties, oxygen permeability, water vapor transmission rate, and morphological features of the resultant biocomposites were characterized. First of all, it was seen that the elongation at break and tensile strength properties of single biopolymers can be combined in binary structures. Then, by establishing triple blend structures, biocomposite films with improved properties were obtained. In addition, the effects of alternative polybutylene succinate (PBS) and polylactic acid (PLA) biopolymers to PBAT biopolymer in triple bioblends were examined. As a result of the studies it was found that the PHBV/PBAT/PHA structure could be developed with functional additives in order to reach the best flexible packaging formula. It was found that the oxygene transmission rate (OTR) value was improved compared to PE with PHA, PHBV and HPMC additives, decreased to 29 cc/m2.day with PBS and 14 cc/m2.day with PLA added to the structure.

Spectroscopic investigation demonstrating the enhancement of the linear/nonlinear optical properties of PVA: BSA blend films

The aim of this study was to prepare novel blend films of poly(vinyl alcohol):bovine serum albumin at different concentrations (96:4, 92:8, 88:12, and 94:16 wt/w%) for use in optoelectronic applications. Linear optical parameters were determined from transmittance and reflectance spectra using spectroscopic data in the range 400–2500 nm. Absorption coefficient analysis gives the type of bandgap transition. The calculated values of absorption edge and optical bandgap energy were increased when the BSA content increased to 8 wt% and then decreased when BSA increased to 16 wt%. The values of Urbach energy and bandgap energy have opposite behavior to each other. Absorption and refraction indices and related parameters were calculated. The data showed significant variations that lead to improved optical parameters and confirm that photon-electron interactions in the films change. The Wemple-DiDomenico model was used to evaluate the dispersion energies and related parameters. The dispersion energy values increase from 3.412 to 12.206 eV, while the oscillator energy values decrease from 6.104 to 4.696 eV and then increase to 6.677 eV with increasing BSA content to 16 wt%. The Eo/(Eg)d ratio is found in the range 1.82–2.82 which may coincide with the prediction of a single oscillator model. Other important dielectric-optical parameters were discussed. Some nonlinear optical properties were also evaluated. Increasing the amount of BSA increased the nonlinear parameters which is beneficial for enhancing local polarization of the blend. All studied parameters are discussed and linked together. The results obtained from this study suggest that these prepared blends can be used in numerous optical applications.

Reconstructing the 3D Coordinates of Guest:Host OLED Blends with Single Atom Resolution.

The performance of electronic and semiconductor devices is critically dependent on the distribution of guest molecules or atoms in a host matrix. One prominent example is that of organic light-emitting diode (OLED) displays containing phosphorescent emitters, now ubiquitous in handheld devices and high-end televisions. In such OLEDs the phosphorescent guest [normally an iridium(III)-based complex] is typically blended into a host matrix, and charge injection and transport, exciton formation and decay, and hence overall device performance are governed by the distribution of the emissive guest in the host. Here high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) is used with depth sectioning to reconstruct the 3D distribution of emissive iridium(III) complexes, fac-tris(2-phenylpyridine)iridium(III) [Ir(ppy)3], blended into the amorphous host material, tris(4-carbazoyl-9-ylphenyl)amine (TCTA), by resolving the position of each single iridium(III) ion. It is found that most Ir(ppy)3 complexes are clustered with at least one other, even at low concentrations, and that for films of 20wt.% Ir(ppy)3 essentially all the complexes are interconnected. The results validate the morphology of blend films created using molecular dynamics simulations which mimic the evaporation film-forming process and are also consistent with the experimentally measured charge transport and photophysical properties.

High energy storage performance in poly(vinylidene fluoride)-based all-organic composites via optimizing the structure of semiconductive filler

The great demand for miniaturization and lightweight energy equipment stimulates the fast development of polymer-based dielectrics with low density and easy processability. Unfortunately, the low energy density puts barriers to the development of polymer dielectrics in the new energy industry. In this work, poly(vinylidene fluoride) (PVDF)-based blending films are prepared and the energy storage properties are explored by regulating the content and structure of semiconductive polymer fillers. The experiment results show that when poly{2-((3,6,7,10,11-pentakis(hexyloxy)triphenylene-2-yl)oxy)ethyl methacrylate} (P6) filler is added, 0.25 wt%-P6/PVDF film attains the maximal discharge energy density (Ud) of 19.1 J cm−3 at 624 MV m−1. Compared with poly{2-((3,6,7,10,11-pentabutoxytriphenylen-2-yl)oxy)ethyl methacrylate} (P4) filler, the P6 filler possesses better compatibility with PVDF and creates deeper traps to suppress the carrier migration and achieve the higher breakdown strength. This research offers useful references for the design of polymer-based composites with excellent energy density through blending triphenylene semiconductive fillers.

Design and Synthesis of Dibenzothiadiazolopyrrolothiophene (DBTPT)‐Based Acceptors for Efficient Organic Photovoltaic Cells

AbstractThe central core in non‐fullerene acceptors (NFAs) plays a crucial role in determining the efficiency of organic photovoltaic (OPV) cells. To further advance the development of OPV cells, it is crucial to synthesize novel central cores for constructing high‐performance NFAs. Here, dibenzothiadiazolopyrrolothiophene (DBTPT) is introduced, a ladder‐type [1,2,5]thiadiazolo[3,4‐e]indole‐fused pentacyclic thiophene unit, into photovoltaic materials. By employing the DBTPT unit as the rigid molecular backbone and modifying the side chain of the thiophene π‐bridge, two new acceptor‐π‐acceptor’‐donor‐acceptor’‐π‐acceptor (A‐π‐A'DA’‐π‐A)‐type acceptors (T6 and T9) are synthesized. The effects of lateral alkyl and alkoxy side chains on the optoelectronic properties, charge transport, and molecular packing order are systematically investigated. When blended with polymer donor Poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b']dithiophene))‐alt‐(5,5‐(1',3'‐di‐2‐thienyl‐5'7'‐bis(2‐ethylhexyl)benzo[1',2'‐c:4',5'‐c']dithiophene‐4,8‐dione))] (PBDB‐T), the blend film based on T9 with alkoxy side chains shows favorable molecular stacking and phase separation, resulting in excellent charge transfer performance. Benefiting low energetic disorder, PBDB‐T:T9‐based cell achieves an efficiency of 12.6% with a markedly low energy loss of 0.568 eV. The preliminary results demonstrate that the DBTPT unit has great potential for the construction of novel NFAs for high‐performance OPV cells.

Influence of γ irradiation on the optical and colour characteristics of the polyvinyl alcohol/polyvinyl pyrrolidone blend film

With the aid of a solution casting technique, we created a blended film made of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP). Gamma doses (5-40 kGy) were applied to samples of the synthetic PVA/PVP film. UV spectroscopy and the CIE colour alterations procedure were used to investigate the impact of the γ dose on the optical features of the synthesized film. The direct optical bandgap (Eg), affected by cross-linking, destroyed the crystalline structure and formed the amorphous regions, dropped from 2.53 to -2.08 eV with the increase in γ dose to 40 kGy. Thus, the PVA/PVP film's compact structure increases. The films displayed a transition which was directly allowed as the ϵ'' vs. hν plots revealed Eg approximately equal to the values derived from Tauc's equation. The colour variances, between the unaltered and irradiated films, were also identified. Significant colour differences could be seen in the pure PVA/PVP film.

Comparative Study on Structural, Dielectric Behavior and AC Conductivity of PPY-PVA Incorporated with TiO2 Fine and Nano Particles

Abstract An in-situ oxidative chemical polymerization technique to prepare thin films of PPY, PVA, and PPY-PVA blend doped with variable concentrations of TiO2 fine- and nano-particles was further investigated by X-ray diffractometer (XRD) and impedance spectrometer to study structural, dielectric, and AC conducting behavior. XRD spectra established that sharp and high intense peaks of PPY-PVA- fine TiO2 films indicated more crystallinity, which might be due to higher compactness and modification in interplanar spacing. Dielectric plots revealed that PPY-PVA-nano TiO2 films exhibited higher dielectric constants and lower dielectric loss compared to films of PPY-PVA- fine TiO2 in shorter frequency region, suggesting that these films are more suitable for charge storage devices. Conductivity plots revealed that AC conductivity of pure PPY was low (4.8 x10-3 S/cm at 313 0K) and was increased to 5.3 x10-3 S/cm by addition of PVA. AC conductivities of PPY-PVA-nano TiO2 thin films are relatively higher (7.43x10-3 S/cm to 1.14x10-2 S/cm) than PPY-PVA-fine TiO2 films (6.35x10-3 to 9.78x10-3 S/cm) with increasing frequency and temperature, which could be due to large surface area to volume ratio of nano-size dopant. This suggests that PPY-PVA-nano TiO2 thin films may be used for sensing various gasses.

Tuning low frequency dielectric properties of flexible ternary polymer blend film reinforced with bio- ionic liquid for the application in green electronics

Biofriendly conducting polymeric blends and composites exhibiting high dielectric constant and dielectric loss are promising for applications as sensors, actuators, microwave absorbing materials, fuel cells and biomedical applications. A great deal of work is reported on using fillers such as conductive nanomaterials, bio ceramics, carbon nanotubes, graphene etc in blends of Polyvinylchloride, Polyvinylpyrrolidone, Polymethylmethacrylate, Polyvinyl alcohol with conducting polymer Polypyrrole, Polyaniline for enhancing their conductivities, tailoring dielectric and electrical, thermal and surface properties of such polymeric materials. However, appropriate dispersion of such fillers in polymeric matrices remains technically challenging. In this regard, bio-ionic liquids have emerged as a novel class of materials and their combination with specific polymer blends opens the possibility to develop smart novel materials with different morphologies. Present work aims to explore the low frequency dielectric properties exhibited by free standing, flexible, biofriendly/biodegradable ternary polymer blend film of Polyvinylchloride-Polyvinylpyrrolidone-Polypyrrole reinforced with choline acetate. The detailed analysis of low frequency dielectric properties authenticates that addition of choline acetate result in modifying the dielectric properties of ternary polymer blend film.. The harmlessness of these films was confirmed from disk diffusion test indicating their benign nature towards (Escherichia coli) (CFT073) and (Bacillus subtilis). Therefore, the developed films can potentially be used for various scale multifunctional dielectric and electrical applications working in close contact with living matter, green electronics and various health monitoring systems.

Dynamic Thermosetting Resins with Synergistic Enhanced Strength and Toughness through Combination with Rigid and Soft Microdomains.

Preparation of materials that possess highly strong and tough properties simultaneously is a great challenge. Thermosetting resins as a type of widely used polymeric materials without synergistic strength and toughness limit their applications in some special fields. In this report, an effective strategy to prepare thermosetting resins with synergistic strength and toughness, is presented. In this method, the soft and rigid microspheres with dynamic hemiaminal bonds are fabricated first, followed by hot-pressing to crosslink at the interfaces. Specifically, the rigid or soft microspheres are prepared via precipitation polymerization. After hot-pressing, the resulting rigid-soft blending materials exhibit superior strength and toughness, simultaneously. As compared with the precursor rigid or soft materials, the toughness of the rigid-soft blending films (RSBFs) is improved to 240% and 2100%, respectively, while the strength is comparable to the rigid precursor. As compared with the traditional crushing, blending, and hot-pressing of rigid or soft materials to get the nonuniform materials, the strength and toughness of the RSBFs are improved to 168% and 255%, respectively. This approach holds significant promise for the fabrication of polymer thermosets with a unique combination of strength and toughness.

Physicochemical, thermal, and mechanical properties of hemicellulose/carboxymethyl cellulose blend films: the influence of blending composition

Physicochemical, thermal, and mechanical properties of hemicellulose/carboxymethyl cellulose blend films: the influence of blending composition

Characterization of hemicellulose‐carboxymethyl cellulose blend films: Enhancement of the physicochemical, thermal, and mechanical properties

AbstractThis study investigates the influence of hemicellulose (Hc) on the chemical composition, thermal stability, mechanical properties, and morphology of carboxymethyl cellulose (CMC). Hc was isolated from oil palm trunk and then added into CMC at 10–30 wt% to prepare Hc‐CMC films via solution casting method. The addition of Hc resulted in reduced visual transparency, rendering the blend films opaque. Fourier transform infrared spectroscopy verified the chemical interaction between Hc and CMC by revealing persistent and robust hydrogen bonding at specific spectral peaks (3483–3045 cm−1). The interaction between Hc and CMC was further indicated by the rougher interfacial structure as revealed in scanning electron microscopy (SEM). Thermal analysis via differential scanning calorimetry and thermogravimetry analysis indicated a decrement in thermal stability as Hc loadings increased in the CMC films. The highest tensile properties were observed in Hc‐CMC blend films at a 20 wt% Hc loading, showcasing notable enhancement about 23%. The 20 wt% Hc‐CMC blend films appeared as more suitable blending composition which having an enhanced physicochemical, thermal, and mechanical properties. This finding underscores its potential applicability in diverse industrial sectors, particularly in packaging applications.

Ligand-Directed Self-Assembly of Organic-Semiconductor/Quantum-Dot Blend Films Enables Efficient Triplet Exciton-Photon Conversion.

Blends comprising organic semiconductors and inorganic quantum dots (QDs) are relevant for many optoelectronic applications and devices. However, the individual components in organic-QD blends have a strong tendency to aggregate and phase-separate during film processing, compromising both their structural and electronic properties. Here, we demonstrate a QD surface engineering approach using electronically active, highly soluble semiconductor ligands that are matched to the organic semiconductor host material to achieve well-dispersed inorganic-organic blend films, as characterized by X-ray and neutron scattering, and electron microscopies. This approach preserves the electronic properties of the organic and QD phases and also creates an optimized interface between them. We exemplify this in two emerging applications, singlet-fission-based photon multiplication (SF-PM) and triplet-triplet annihilation-based photon upconversion (TTA-UC). Steady-state and time-resolved optical spectroscopy shows that triplet excitons can be transferred with near unity efficiently across the organic-inorganic interface, while the organic films maintain efficient SF (190% yield) in the organic phase. By changing the relative energy between organic and inorganic components, yellow upconverted emission is observed upon 790 nm NIR excitation. Overall, we provide a highly versatile approach to overcome longstanding challenges in the blending of organic semiconductors with QDs that have relevance for many optical and optoelectronic applications.

A tear-free and edible dehydrated vegetables packaging film with enhanced mechanical and barrier properties from soluble soybean polysaccharide blending carboxylated nanocellulose

The aim of the study was to develop soybean polysaccharide (SSPS) -carboxylated nanocellulose (CNC) blending films with enhanced mechanical and barrier properties to be used as a tear-free and edible packaging materials. The films were formed by casting method, with CNC as the strengthening unit and glycerol as the plasticizer. The effect of CNC on structural and physical performances of the SSPS-CNC films were studied. SEM indicated that the film will stratify with excess CNC (10 %), but the film remains intact and compact. Incorporation of CNC into SSPS films did not change peak position in the XRD pattern significantly. Hydrogen bonds among SSPS, glycerol and CNC were indicated by the FTIR spectra. The compounding of CNC greatly lessened the light transmittance and hydrophilicity (CA increased from 55.42° to 70.67°), but perfected the barrier (WVP decreased from 3.595 × 10−10 to 2.593 × 10−10 g m−1 s−1 Pa−1) and mechanical properties (TS improved from 0.806 to 1.317 MPa). The results of packaging dehydrated vegetable indicated that the SSPS-8CNC film can effectively inhibit the packaged cabbage absorption water vapor. As a consequence, SSPS film perfected by CNC is hopeful to pack dehydrated vegetables in instant foods.

Selenium substitution for dielectric constant improvement and hole-transfer acceleration in non-fullerene organic solar cells

Dielectric constant of non-fullerene acceptors plays a critical role in organic solar cells in terms of exciton dissociation and charge recombination. Current acceptors feature a dielectric constant of 3-4, correlating to relatively high recombination loss. We demonstrate that selenium substitution on acceptor central core can effectively modify molecule dielectric constant. The corresponding blend film presents faster hole-transfer of ~5 ps compared to the sulfur-based derivative (~10 ps). However, the blends with Se-acceptor also show faster charge recombination after 100 ps upon optical pumping, which is explained by the relatively disordered stacking of the Se-acceptor. Encouragingly, dispersing the Se-acceptor in an optimized organic solar cell system can interrupt the disordered aggregation while still retain high dielectric constant. With the improved dielectric constant and optimized fibril morphology, the ternary device exhibits an obvious reduction of non-radiative recombination to 0.221 eV and high efficiency of 19.0%. This work unveils heteroatom-substitution induced dielectric constant improvement, and the associated exciton dynamics and morphology manipulation, which finally contributes to better material/device design and improved device performance.