Conductivity Of Films Research Articles

Enhancement of electrical and photo-electrical properties of P3HT:CrCl2 thin films for photo sensing applications

Abstract In this work, doped and undoped P3HT thin films are prepared and deposited onto ITO interdigitated electrodes. To improve the optical and the electrical properties of the pure P3HT thin film, chromium(II) chloride was used as dopant material with three different weight percentage, 2.5%, 5%, 10%. Room-temperature current-voltage (I-V) characteristics of the samples were measured, showing an increase in the electrical current with increasing the dopant concentration. Under dark condition, the conductivity and resistivity of the pure P3HT thin films were enhanced by a factor of 5x as a result of doping the P3HT by 10 wt.% of CrCl2. Under light intensity (50 mW/cm2) and at 10 V bias, the conductivity and resistivity obtained from P3HT:CrCl2 (10 wt.%) thin films are 4.75x10-4 S/cm and ~2 kΩ, respectively. These results exhibit an enhancement by a factor of ~12x compared to those obtained from pure P3HT thin film. The current of the photo-sensors based on doped/undoped P3HT thin films are measured as a function of time under light intensity ranging from 0 to 50 mW/cm2 at 1 V bias, exhibiting high photo-response and good reproducibility. Three different wavelengths, white, green, and red were used as light sources to expose the photo-sensors. Under white light, photo-sensor based on P3HT:CrCl2(10 wt.%) exhibit the highest values of the photo-responsivity and quantum efficiency, ~23.3 mA/W and 5.8%, respectively, showing an enhancement by a factor of ~ 11.5x compared to those obtained from the photo-sensor based on pure P3HT.

Enhanced current-carrying capability in YBCO coated conductor bilayers for high-field applications

We have investigated the impact of bilayer structures on the critical current density, J c, of YBa2Cu3O6+x (YBCO) coated conductor films, i.e. films grown on buffered metal substrates, under varying temperature and magnetic field conditions. The bilayers consisted of a YBCO layer free of artificial pinning centers and 8 wt% BaZrO3-added (BZO) layer on top, where the thickness percentage of the layers was varied from 0 to 100 %. The results reveal that the bilayer configuration enhances J c at temperatures below 60 K, with a significant improvement in high magnetic fields (5–8 T) and temperatures ≤20 K. The optimal BZO-added layer thickness was found to be approximately 70 %, reaching 80 % at 8 T. Structural examinations indicate improved growth of YBCO and BZO nanorods in the bilayer structure with BZO-added layer thickness ≤80 %. Theoretical model of the bilayer structure considering the layers as two parallel superconductors with different properties was developed. It was found that the model adequately explains all the experimentally observed tendencies, and thus the observed maximum in J c is due to better growth of the BZO-added layer. The study provides valuable insights for designing optimal bilayer structures for diverse applications operating in different temperature and magnetic field regimes.

Laser-assembled conductive 3D nanozyme film-based nitrocellulose sensor for real-time detection of H2O2 released from cancer cells

In this work, a nanostructured conductive film possessing nanozyme features was straightforwardly produced via laser-assembling and integrated into complete nitrocellulose sensors; the cellulosic substrate allows to host live cells, while the nanostructured film nanozyme activity ensures the enzyme-free real-time detection of hydrogen peroxide (H2O2) released by the sames. In detail, a highly exfoliated reduced graphene oxide 3D film decorated with naked platinum nanocubes was produced using a CO2-laser plotter via the simultaneous reduction and patterning of graphene oxide and platinum cations; the nanostructured film was integrated into a nitrocellulose substrate and the complete sensor was manufactured using an affordable semi-automatic printing approach. The linear range for the direct H2O2 determination was 0.5–80 μM (R2 = 0.9943), with a limit of detection of 0.2 μM. Live cell measurements were achieved by placing the sensor in the culture medium, ensuring their adhesion on the sensors' surface; two cell lines were used as non-tumorigenic (Vero cells) and tumorigenic (SKBR3 cells) models, respectively. Real-time detection of H2O2 released by cells upon stimulation with phorbol ester was carried out; the nitrocellulose sensor returned on-site and real-time quantitative information on the H2O2 released proving useful sensitivity and selectivity, allowing to distinguish tumorigenic cells. The proposed strategy allows low-cost in-series semi-automatic production of paper-based point-of-care devices using simple benchtop instrumentation, paving the way for the easy and affordable monitoring of the cytopathology state of cancer cells.

A new strategy for fabricating low haze p-type CuI film

As an intrinsic p-type transparent conductor with a wide band gap of 3.1 eV, γ-CuI full of potential has gradually attracted the attention of researchers. However, γ-CuI films deposited by various techniques generally exhibit high haze with a frosted glass-like appearance, which significantly affects the device performance. Herein, a new strategy is proposed in which true p-type CuI thin films with low haze have been successfully synthesised at room temperature. The specular transmittance of the CuI film over 85% in the visible region (400–800 nm) can be achieved. The haze of the as-prepared γ-CuI films can be as low as 0.7%. Meanwhile, the as-prepared CuI film has an FOM as high as 230 MΩ−1. This ideal stable p-type optoelectronic performance was significant among various typical p-type transparent conductive films.

Ag-thiolate interactions to enable an ultrasensitive and stretchable MXene strain sensor with high temporospatial resolution.

High-sensitivity strain sensing elements with a wide strain range, fast response, high stability, and small sensing areas are desirable for constructing strain sensor arrays with high temporospatial resolution. However, current strain sensors rely on crack-based conductive materials having an inherent tradeoff between their sensing area and performance. Here, we present a molecular-level crack modulation strategy in which we use layer-by-layer assembly to introduce strong, dynamic, and reversible coordination bonds in an MXene and silver nanowire-matrixed conductive film. We use this approach to fabricate a crack-based stretchable strain sensor with a very small sensing area (0.25 mm2). It also exhibits an ultrawide working strain range (0.001-37%), high sensitivity (gauge factor ~500 at 0.001% and >150,000 at 35%), fast response time, low hysteresis, and excellent long-term stability. Based on this high-performance sensing element and facile assembly process, a stretchable strain sensor array with a device density of 100 sensors per cm2 is realized. We demonstrate the practical use of the high-density strain sensor array as a multichannel pulse sensing system for monitoring pulses in terms of their spatiotemporal resolution.

Carbon nanotube-grid infrared transparent electrodes for flexible electrochromic devices with visible to mid-infrared dual-band modulation

Flexible mid-infrared electrochromic devices (MIR-ECDs) have attracted wide attention due to the growing demands for thermal camouflage and body comfort. However, the normal conductive films (e.g., indium tin oxide/polyethylene terephthalate (ITO/PET) films) are unsuitable for MIR-ECDs due to low infrared transmittance. Herein, the infrared transparent carbon nanotube (CNT) grid films were prepared by designing the grid structure. The infrared transmittance of CNT grid film could reach 72 %; meanwhile, the visible transmittance could reach 75 %. The CNTs exhibited infrared modulation under different voltages due to the doping/de-doping of ions in electrolytes into the CNT network. The flexible electrochromic devices with visible to mid-infrared dual-band modulation were prepared by using CNT grid film as the electrode and poly (3,4 ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) as the electrochromic layer, which could realize the infrared synergistic modulation of PEDOT:PSS and CNT grid in the mid-infrared range and reversible color changes between light blue and dark blue in the visible range, showing promising applications in adaptive camouflage and thermal management.

Preparation of CNT/CNF/PDMS/TPU Nanofiber-Based Conductive Films Based on Centrifugal Spinning Method for Strain Sensors.

Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors.

Highly Thermally Conductive Super-Aligned Boron Nitride Nanotube Films for Flexible Electronics Thermal Management.

Flexible electronics toward high integration, miniaturization, and multifunctionality, leading to a dramatic increase in power density. However, the low thermal conductivity of flexible substrates impedes efficient heat dissipation and device performance improvement. In this work, we propose a template-assisted chemical conversion strategy for obtaining boron nitride nanotube (BNNT) films with high thermal conductivity and great flexibility. Aligned carbon nanotube (CNT) films have been adopted as templates; a low-temperature chemical conversion followed by a high-temperature annealing has been carried out to produce a highly ordered BNNT film. Benefiting from the high orientation order, the BNNT film exhibits an exceptional thermal conductivity of 45.5 W m-1 K-1 and presents excellent heat dissipation capability, much superior to the commonly used polyimide film. Furthermore, the BNNT film demonstrated excellent flexibility and high insulation resistance. The test of integration with film resistors demonstrated its potential as a thermally conductive substrate for electronics cooling. This work provides a solution for the effective thermal management of flexible electronics.

Flexible conductive polymer composite film with sandwich-like structure for ultra-efficient and high-stability electromagnetic interference shielding

Flexible electromagnetic interference (EMI) shielding films with the merits of light-weight, flexibility, and high EMI shielding performance are the essential materials for the consumer electronics and communication products. Herein, we construct a hybrid conductive network based on the electrospinning thermoplastic polyurethane (TPU) film loaded with different dimensional conductive fillers, including 0D FeCl3, 1D carbon nanotube (CNT) and 2D graphene nanosheet (GN), which fabricate a flexible, light-weight, and ultra-efficient EMI shielding composite film. In specific, the electrospinning porous TPU film is firstly anchored by CNTs assisted by ultrasound to generate the porous TPU/CNT film. Thereafter, the as-prepared porous TPU/CNT film is filtered by GN/CNT/FeCl3 solution to generate a double-layer GN/CNT/FeCl3@TPU/CNT film. Finally, another porous TPU/CNT film is sealed onto the GN/CNT/FeCl3@TPU/CNT film by hot-pressing, which fabricates a sandwiched TPU/CNT@GN/CNT/FeCl3@TPU/CNT composite film. It is interesting to note that the composite film possesses the ultrahigh EMI shielding value (56.0 dB at 10.0 GHz) in the X-band (8.2-12.4 GHz) with high flexibility, excellent mechanical properties, long-term durability (acid-base environment resistance and stability after 1000 bends), as well as high thermal conductivity (6.53 W/(m K)). This work proposes a simple but efficiency strategy to design the flexible EMI shielding film with ultra-high performance and outstanding durability.

Bidirectional large strain monitoring using a novel graphene film-based patch antenna sensor

This study proposes a rectangular microstrip patch antenna sensor based on a high-conductivity graphene film for bidirectional strain detection in structural health monitoring (SHM). By using a highly conductive graphene film instead of traditional metal foil to produce a patch antenna, the antenna possesses a higher flexibility and a larger sensing range. The mechanical, electromagnetic, and radiative properties were investigated. The strain sensing principle based on the resonant frequency offset of the graphene film antenna was proposed. The relationships between the resonant frequency shift and structural strain were quantitatively explored through theoretical deductions, finite element simulations, and experiments. According to the experimental results, the shift in the resonant frequency was linearly related to the lateral and longitudinal strains. The sensitivity coefficients for the lateral and longitudinal strains were 2.2037 kHz/μϵ and 3.6198 kHz/μϵ, respectively. The thermal strain can be distinguished based on the linear resonant frequency-temperature relationship. The results demonstrated the advantages and prospects of the proposed novel patch antenna for SHM.

Investigation of structural, morphological and optoelectronic properties of (Ni, Co)-doped and (Ni/Co) co-doped SnO2 (110) sprayed thin films

The manuscript details the application of spray pyrolysis for the deposition of an economically viable transparent conductive oxide film comprised of (Ni/Co) co-doped SnO2 on a glass substrate. The primary objective of this research was to systematically examine the impact of Ni/Co co-doping on diverse properties of the SnO2 thin film. These properties encompassed the film's structural composition, surface morphology, optical response, and electrical behaviors. A comparison was made with pure SnO2 film, as well as SnO2 films doped with 3 %Ni and 1 %Co. The results indicate that all the samples exhibited a tetragonal structureThe introduction of Co and Ni atoms had no impact on the favored alignment of the (110) plane or the crystal structure of the SnO2 film. The crystallite size of the pure SnO2 film, as well as the (Co, Ni)-doped and (Ni/Co) co-doped SnO2 films, varied within the range of 11 to 20 nm. Scanning electron microscopy (SEM) images were employed to assess how doping and co-doping influenced the surface characteristics of the films. The presence of pores and/or roughness on the surface resulted in a hydrophilic character and a decrease in the contact angle for the doped films (Ni, Co). However, the co-doped film exhibited a hydrophobic characteristic due to the surface enhancement provided by SnO2:3 %Ni:1 %Co. The research also focused on the optical characteristics of the films, showing a positive impact with the proper incorporation of Ni and Co atoms into the SnO2 lattice. It was notably observed that the addition of Ni and Co atoms improves the optical properties of the undoped transparent SnO2 film in the visible spectrum, with a high transmittance of 87 % achieved for the Ni-doped film. Furthermore, the hydrophobic nature achieved by adding a concentration of 3 %Ni to the SnO2:1 %Co film enhances its optical transmission in the range of 300 nm to 750 nm. The SnO2 film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 2.22 × 10−2 Ω.cm for the film (3 %Ni/1 %Co)-SnO2. Drawing from these insightful results, the study proposes the potential utilization of (Ni/Co) co-doped SnO2 films as transparent electrodes in optoelectronic applications, especially in the manufacturing of thin film solar cells.

Enhanced microwave and far IR absorption of nanometer thin conductive films in the case of total internal reflection

Enhanced microwave and far IR absorption of nanometer thin conductive films in the case of total internal reflection

The Janus Structure of Graphene Oxide and Its Large-Size Conductive Film Strip Pattern.

In this paper, the oxidation-exfoliation process of graphite is studied experimentally by the mixed-solvent method, the oxidation-exfoliation process of graphite is simulated theoretically, and it is found that Graphene Oxide (GO) is a Janus structure with inconsistent oxidation on both surfaces; hydrophilic on one side and hydrophobic on the other side. This layer structure and layer spacing are due to the inconsistent oxidation on both sides which changes with the polarity of different solvent mixtures. We used a two-phase system of benzyl alcohol and water, as well as controlling the polarity of the surface of the substrate, to achieve (using a mixed solution of GO which has a selectivity more inclined to the oil phase when the aqueous phase is present) the preparation of reduced graphene oxide patterns. We also used a complex solution of hydrogen iodide and a sodium-iodide complex solution for secondary reduction to enhance its conductivity to 8653 S/m.

Anomalous size effects of ultra-small graphene sheets on the thermal properties of macroscopic films

Graphene films assembled from graphene nanosheets have achieved a wide range of applications in thermal management due to their ultra-high thermal conductivity. Although it is well established in the micron range that increasing the lateral size of graphene sheets enhances the thermal conductivity of graphene films. However, the preparation of large-size graphene sheets and their assembly into ordered film structures remain challenging, which impedes the development of high-performance thermally conductive graphene films. Herein, by unifying the properties of graphene sheets and preparation processes, we correlate the thermal conductivity of graphene films and the lateral size of starting sheets ranging from 0.32 to 20.32 μm and probe the underlying mechanism from the perspectives of macroscopic and microscopic structural defects. Surprisingly, decreasing lateral size to 0.32 μm achieved as high in-plane thermal conductivity (K//, 1550.06 ± 12.99 W/mK) and significantly higher through-plane thermal conductivity (K⊥, 8.11 ± 0.08 W/mK) of graphene films as the case of 20.32 μm. Besides, the commonly overlooked size effect of K⊥ shows an unexpected negative correlation, and the size effect of K// is also not monotonically increasing. These phenomena are correlated with micro-structure defects and lattice defects. Mechanism analysis reveals that thermally induced gas generation and the complex gas-sheet interactions during micro-structure evolution play a critical role in the size effect and may explain the unexpected negative size effect in the sub-micro range. These findings in size effects provide theoretical guidance for the selection of raw materials in fabricating highly thermally conductive graphene films.

Enhancing Thermal Conductivity of Graphene Films via Secondary Graphitization under a Direct Current Arc

Enhancing Thermal Conductivity of Graphene Films via Secondary Graphitization under a Direct Current Arc

Ion-Exchange Polymer Network Enhanced Interfacial Compatibility for Stable and Efficient Inverted Perovskite Solar Cells.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a low-cost and water-processable hole transport material has been widely used in various optoelectronic devices. Although the incorporation of anionic polyelectrolyte PSS in PEDOT contributes to superior water solubility, the trade-off between efficiency and stability remains a challenging issue, limiting its reliable application in perovskite solar cells (PSCs). Herein, we proposed an ion-exchange (IE) strategy to effectively control the doping degree, interfacial charge dynamics, and reliability of PEDOT:PSS in PSCs. This IE approach based on hard cation-soft anion rules enabled effective anion exchange between PEDOT:PSS and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), which favored enhancing the film conductivity, regulating the perovskite crystallization, and reducing the carrier losses at the interfaces. Consequently, a notable increase of the open-circuit voltage from 0.88 to 1.02 V was realized, resulting in a champion efficiency of 18.7% compared to the control (15.4%) in inverted PSCs. More encouragingly, this IE strategy significantly promoted the thermal and environmental stability of unsealed devices by maintaining over 80% of initial efficiencies after 2000 h. This work provides an effective way to regulate the doping state of the PEDOT-based hole transport material and guides the development of robust polymeric conducting materials for efficient perovskite photovoltaics.

Preparation and Properties of Polyaniline/Hydroxypropyl Methylcellulose Composite Conductive Thin Films.

In this work, a chemical grafting polymerization method was employed to synthesize EHPMC-g-PANI self-supporting films. Polyaniline (PANI) was grafted onto hydroxypropyl methylcellulose (HPMC) modified with epichlorohydrin (EPHMC) to obtain an EHPMC-g-PANI aqueous dispersion, which was subsequently dried to form the self-supporting films. The introduction of HPMC, with its excellent film-forming ability and mechanical strength, successfully addressed the poor film-forming ability and mechanical properties intrinsic to PANI. Compared to in situ polymerized HPMC/PANI, the EHPMC-g-PANI exhibited significantly improved storage stability. Moreover, the fabricated EHPMC-g-PANI films displayed a more uniform and smoother morphology. The conductivity of all the films ranged from 10-2 to 10-1 S/cm, and their tensile strength reached up to 36.1 MPa. These results demonstrate that the prepared EHPMC-g-PANI holds promising potential for applications in various fields, including conductive paper, sensors, and conductive inks.

Effects of substrate bias voltage on conductivity and internal stress of TiN films

In order to make the service life of microelectronic devices longer, titanium nitride electrode films need to meet the requirements of high electrical conductivity and low internal stress. In this paper, the effect of substrate bias voltage on the properties of titanium nitride films prepared by direct current (DC) reactive magnetron sputtering was studied systematically. The changes of titanium nitride films properties were investigated in detail from the aspects of resistivity, growth rate, crystal orientation, roughness and internal stress. The results show that the introduction of substrate bias voltage is conducive to the formation of dense titanium nitride films. Considering that the resistivity and internal stress of titanium nitride film vary with substrate bias voltage, the film deposited at substrate bias voltage of -100 V is selected as the electrode film material with the best performance (resistivity of 47.5 μΩ·cm, roughness of 1.1 nm and internal stress of -5.6 GPa).

Fabrication of alcohol sensor using undoped and Al doped ZnO nanostructure film with polymer electrolyte gating

We report the fabrication of two terminal and three terminal gas sensor using Al-doped ZnO nanostructured-films and polymer electrolyte gate dielectric on glass substrate using vacuum free chemical method. The Al doped ZnO films are characterized by UV–vis Spectrometer, SEM, EDX and XRD. The characterization results have revealed the polycrystalline structure of both undoped and doped ZnO; with loosely packed, porous, and spherical granny nanostructure with mean grain size 20–10 nm and bandgap of the films is within the range of 3.12–3.16 eV. The conductivity of the ZnO film is tuned by Al concentration and the maximum value of conductivity was observed in 3 % Al doped ZnO films. Similarly, the best performance index of TFT such as current ON/OFF ratio, high transconductance and low threshold voltage was observed in 3 % Al doping concentration. The ordinary (two-terminal) sensor and three-terminal (FET) sensors' responses towards three different concentrations 50, 250, 500 ppm of ethanol and methanol vapors have been studied. The sensitivity of the film is modulated by Al concentration and higher value of sensitivity was achieved at 3 % Al doped ZnO films. The use of polymer electrolyte enhanced the sensitivity of the device which is more effective in methanol vapor. The Response-Recovery time of the sensor is significantly improved in three terminal devices than the two terminal devices.

Preparation and properties of rGO-Co-NiO composite films: Low attenuation and high coloration efficiency

The study of electrochromic materials has far-reaching significance for the regulation of light and heat as well as the reduction of energy consumption. In this study, rGO-Co-NiO composite films were prepared by combining graphene oxide, which has excellent conductivity and stability, with Co-NiO films. The particle size, band gap, conductivity and response time of the electrochromic films were improved by precisely adjusting the component modulation amount of graphene oxide. The results show that with the incorporation of GO it is easy to form oxygen vacancies, which is conducive to ionic conduction and diffusion, in which the film with a GO doping concentration of 4 % has excellent performances in terms of response time and coloring efficiency, and the response time is reduced from 10.2 to 5.8 seconds, and it still possesses 57.25 % of the light modulation amplitude after 600 cycles, of which the attenuation rate is only 2 % for the period from 100 to 600 cycles, The coloring efficiency after 100 cycles is 48.21 cm2/C. In summary, the investigated rGO-Co-NiO composite films have a broad potential for future application in electrochromic devices.