Indium Tin Oxide Layer Research Articles

Surface Modification of Heterojunction with Intrinsic Thin Layer Solar Cell Electrode with Organosilane

Solar cell (SC) technologies, which are essential in the transition toward sustainable energy, utilize photovoltaic cells to convert solar energy into electricity. Of the available technologies, heterojunction with intrinsic thin-layer (HIT) solar cells offers high efficiency and reliability. The current study explored the enhancement of HIT solar cell performance through the use of 3-aminopropyltrimethoxysilane (APTMS) self-assembled monolayers (SAMs) on the surface of the cells’ indium tin oxide (ITO) layer. Photoluminescence mapping revealed greater brightness and photocurrent in the HIT sample treated with APTMS SAMs, with the results indicating more favorable optical and electrical properties. The application of APTMS SAMs led to higher open-circuit voltage, fill factor, maximum power output, and efficiency by passivating the ITO surface and achieving energy level alignment, thereby enhancing the charge carrier dynamics. These findings demonstrate the potential of APTMS SAMs to improve HIT solar cell efficiency and reliability.

Effect of current spreading layer on Internal Quantum efficiency and optical power of flip chip gallium nitride LEDs with circular contacts

The unique properties of the Indium Tin Oxide (ITO) make it an excellent choice as a current spreading layer in Flip Chip Light Emitting Diodes (FCLEDs) and other optoelectronic devices. Herein, the performance of FCLEDs is analyzed by a precise mathematical model for the current spreading length (Ls) produced by the ITO layer under circular-shaped contacts. The expressions are formulated without approximations using ABC-model for extracting the Internal Quantum Efficiency (IQE, ηint), optical power (Pint) and Emission Intensity (EI). The thickness (tITO) and resistivity (ρITO) of the ITO layer are varied for different current densities, and their adverse effects on IQE are determined. At lower current densities, IQE increases with thickness and decreases for high resistivity of the ITO layer. At higher current densities, there is a gradual decrease in IQE irrespective of the ITO layer presence due to “Efficiency Droop”. The IQE in the proposed work is 82 % at a thickness of 50–200 nm and current density of 8 A/cm2, and the optical power is around 40 mW, showing good agreement with the experimental data, making it feasible for future high-performance FCLEDs.

Tunable optically transparent graphene–ITO patterning-based millimeter-wave absorber

In this work, we demonstrated a multilayer millimeter-wave absorber capable of tuning the absorption frequency while simultaneously maintaining the optical transparency. It comprises indium tin oxide (ITO) as the bottom ground plane deposited over polyvinyl chloride (PVC) substrate over which a patterned ITO layer is formed. Above this ITO layer, a PVC spacer is put to isolate the upper graphene sandwich structure (GSS) comprising of two patterned graphene mediums separated by a diaphragm paper. The configuration shows the tunability of reflectance minima (which correspond to high absorptance of ≥ 98 %) in a frequency range of 92.5–97.5 GHz due to the adjustable bias voltage applied to GSS. Additionally, the designed absorber demonstrates adequate shielding effect, generally required for both commercial and military applications in the stated frequency range. This simultaneously configurable and optically transparent device has potential in multispectral and smart stealth technologies, particularly 6G applications.

Impact of Annealing in Various Atmospheres on Characteristics of Tin-Doped Indium Oxide Layers towards Thermoelectric Applications.

The aim of this work was to investigate the possibility of modifying the physical properties of indium tin oxide (ITO) layers by annealing them in different atmospheres and temperatures. Samples were annealed in vacuum, air, oxygen, nitrogen, carbon dioxide and a mixture of nitrogen with hydrogen (NHM) at temperatures from 200 °C to 400 °C. Annealing impact on the crystal structure, optical, electrical, thermal and thermoelectric properties was examined. It has been found from XRD measurements that for samples annealed in air, nitrogen and NHM at 400 °C, the In2O3/In4Sn3O12 share ratio decreased, resulting in a significant increase of the In4Sn3O12 phase. The annealing at the highest temperature in air and nitrogen resulted in larger grains and the mean grain size increase, while vacuum, NHM and carbon dioxide atmospheres caused the decrease in the mean grain size. The post-processing in vacuum and oxidizing atmospheres effected in a drop in optical bandgap and poor electrical properties. The carbon dioxide seems to be an optimal atmosphere to obtain good TE generator parameters-high ZT. The general conclusion is that annealing in different atmospheres allows for controlled changes in the structure and physical properties of ITO layers.

Thickness Optimization of Front and Recombination ITO in Monolithic Perovskite/Silicon Tandem Solar Cells

Optical losses of perovskite/silicon tandem solar cells can be effectively reduced by optimizing the thin‐film layer thicknesses. Herein, the thicknesses of DC sputtered indium tin oxide (ITO) films, which serve as the front electrode and the recombination layer connecting the subcells, are optimized to reach high transparency and good lateral charge transport simultaneously. Optical simulations of the full perovskite/silicon tandem solar cell stacks are performed to find the optimum recombination and front electrode ITO thicknesses for solar cells as well as modules. Implementation of the optimized 25 nm front electrode ITO thickness in semitransparent single‐junction perovskite solar cells increases the short‐circuit density by 1.5 mA cm−2 compared to the former reference thickness of 75 nm. Combined with an optimized 20 nm recombination ITO layer, high short‐circuit density of 20.3 mA cm−2 is reached in perovskite/silicon tandem solar cell devices, which is the highest reported value for planar front perovskite/silicon tandem solar cells to the best of knowledge. Further interface passivation enables 28.8% power conversion efficiency.

Ultrathin Indium Tin Oxide Accumulation Mode Electrolyte‐Gated Transistors for Bioelectronics

AbstractElectrolyte‐gated field effect transistors and electrochemical transistors have emerged as powerful components for bioelectronic sensors and biopotential recording devices. A set of parameters must be considered when developing devices to amplify weak electrophysiological signals. These include maximum transconductance values, cut‐off frequencies, and large on/off current ratios. Organic polymer‐based devices have recently dominated the field, especially when considering flexibility as a key factor. Oxide semiconductors may also offer these features, as well as advantages like higher mobility. Herein, flexible, ultrathin, indium tin oxide (ITO) electrolyte‐gated transistors are reported. These accumulation‐mode devices combine n‐type operation with µe = 9.5 cm2 Vs−1, high transconductance (gm = 44 mS), and on/off ratios (105) as well as optically transparent layouts. While oxides are normally considered brittle, mechanically flexible ITO layers are obtained by room temperature deposition of amorphous layers onto parylene C. This process results in low strain, producing devices that survive bending. ITO electrochemically degrades, however, with cycling. To overcome this, the surface is passivated with high dielectric constant inert capping layers of Ta2O5 or Ta2O5/AlN. This greatly improves stability while preserving low gate voltages. Based on their overall performance, ITO‐based EGFETs are promising for bioelectronics.

Boosting third-order optical nonlinearity in ITO/Au multilayer films via interfacial effects

We present the enhancement of third-order optical nonlinearity in indium tin oxide (ITO)/Au multilayer films via interfacial effects. The overall thickness of prepared ITO and Au layer was kept as 200 nm and 14 nm, respectively, and thus multilayers are 214 nm, i.e., for the sandwich structure ITO/Au/ITO, the thickness of ITO and Au is 100 nm and 14 nm, respectively, while the thickness of ITO and Au is 40 nm and 3.5 nm in the nine-layer films composed of five layers of ITO and four layers of Au. The measured nonlinear refractive index (n2) and absorption coefficient (β) of the multilayers rise as the number of layers increases. The maximum n2 and β in the nine-layer film are 2.6×10−14 m2/W and −3.7×10−8 m/W, which are 3.8 and 2.3 times larger than the values in the pure ITO film, respectively. Such enhancement of optical nonlinearity as the number of layers increases originates from the increase of carrier concentrations in multilayers due to contact of metals/semiconductors (interfacial effects), not following the traditional effective media theory and epsilon-near-zero effect. The results pave a way to modulate the optical nonlinearity in special metal-dielectric multilayers of interfacial effects and indicates the promising applications in nonlinear photonics.

Optimum Design of InGaN Blue Laser Diodes with Indium-Tin-Oxide and Dielectric Cladding Layers.

The efficiency of current GaN-based blue laser diodes (LDs) is limited by the high resistance of a thick p-AlGaN cladding layer. To reduce the operation voltage of InGaN blue LDs, we investigated optimum LD structures with an indium tin oxide (ITO) partial cladding layer using numerical simulations of LD device characteristics such as laser power, forward voltage, and wall-plug efficiency (WPE). The wall-plug efficiency of the optimized structure with the ITO layer was found to increase by more than 20% relative to the WPE of conventional LD structures. In the optimum design, the thickness of the p-AlGaN layer decreased from 700 to 150 nm, resulting in a significantly reduced operation voltage and, hence, increased WPE. In addition, we have proposed a new type of GaN-based blue LD structure with a dielectric partial cladding layer to further reduce the optical absorption of a lasing mode. The p-cladding layer of the proposed structure consisted of SiO2, ITO, and p-AlGaN layers. In the optimized structure, the total thickness of the ITO and p-AlGaN layers was less than 100 nm, leading to significantly improved slope efficiency and operation voltage. The WPE of the optimized structure was increased relatively by 25% compared to the WPE of conventional GaN-based LD structures with a p-AlGaN cladding layer. The investigated LD structures employing the ITO and SiO2 cladding layers are expected to significantly enhance the WPE of high-power GaN-based blue LDs.

Quantum Interference at the Recombination Junction of Perovskite-Si Tandem Solar Cells Improves Efficiency.

We show quantum interference effects can enhance coherent electron transmission in perovskite tandem solar cells using ultrathin indium tin oxide (ITO) layers. We develop a model for the behavior of the power conversion efficiency based on a finite difference time domain solution of the time-dependent Schrödinger equation. The modeled potential includes an imaginary part to simulate probability loss by incoherent scattering. The results agree with observations of efficiency as a function of ITO thickness, suggesting an optimized design.

Metal Supported Metal Oxide Catalysts for Hydrogen Peroxide Production Via Water Splitting

The two-electron water oxidation reaction (WOR) has drawn recent attention as an efficient, simple method of producing on-site hydrogen peroxide through electrochemical water splitting. However, finding electrocatalysts with high activity and stability in the reaction’s harsh oxidizing environment is challenging. This is made especially difficult due to the competing four-electron and one-electron WOR, which necessitate a catalyst material with high selectivity towards the hydrogen peroxide production pathway. Here, we utilize metal/metal oxide coupling interactions to tune metal oxide catalysts to be active for 2 e- WOR via the creation of a Mott-Schottky junction. Metal/metal oxide interactions have been well studied for supported metal catalysts, but their behavior has been less investigated for catalysts where the metal oxide provides the active sites, called inverse catalysts. In this case, the difference in work functions between the metal support and metal oxide semiconductor catalyst drives electron transfer between the two, facilitating electronic interactions which can modulate the binding energy of reaction intermediates at the interface and thus tune the catalytic ability of the metal oxide. In this work, we investigate a variety of metal oxide catalyst and metal support materials and find that a thin layer of indium tin oxide (ITO) supported by a layer of platinum (Pt) has excellent catalytic ability towards 2 e- WOR. The activity, selectivity, and stability of the ITO/Pt catalyst shows significant improvement over the unsupported ITO catalyst and yields hydrogen peroxide production rates greater than those reported in literature using other standard catalysts for this reaction. This method of catalyst engineering also provides a future pathway to create new catalysts for this electrochemical reaction. Figure 1

Fabrication of Nano-Carbon-Based Sustainable Perovskite Solar Cells

The rising need for sustainable energy solutions has fuelled considerable research into novel technologies that harness solar energy for efficient and scalable energy storage. Carbon nanotubes (CNTs) have emerged as feasible candidates for these applications due to their unique properties, such as high surface area, better electrical conductivity, and chemical stability.This report focuses on the design and fabrication of cost-effective nano-carbon-based perovskite solar cells (PSCs) and discusses their potential for clean energy generation and storage. This experimental study shows a novel technique to increase the sustainability the conventional fluorine-doped tin oxide (FTO) substrate with an Indium Tin Oxide (ITO) derived from electronic waste and incorporating nanocarbon based-graphene with solution-based techniques. This addition serves as a good basis for the ITO coating, aids charge transport in the perovskite solar cell, and promotes uniform covering maximum electrical conductivity, and transparency. Being the transparent conducting electrode, the CNTs is infused with the upcycled ITO coated glass and was included in the perovskite solar cell architecture, which replaces the traditional ITO electrode, lowering material costs, and improving the circular economy for energy storage devices, and a cleaner energy future.The ITO extraction process entails recovering indium and tin from mobile phones using an environmentally friendly and economical chemical etching process using hydrochloric acid (HCl) to remove the ITO layer. To ensure the purity and structural integrity of the ITO nanoparticles, they were rigorously characterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. After depositing a perovskite- CNTs precursor solution on the ITO layer glass substrate, the light-absorbing layer was annealed. Electron transport and hole-blocking layers were then deposited utilizing solution processing techniques using the PEDOT: PSS and metal electrodes were deposited to complete the device manufacturing. The current-voltage (J-V) relationship was used to compute the open-circuit voltage, short-circuit current density, fill factor (FF), and power conversion efficiency (PCE) of a solar cell. Electrical characterization allow for the calculation of solar cell performance metrics such as short-circuit current (Isc), short-circuit current density (Jsc), and open-circuit voltage (Voc). These findings imply that employing e-waste-derived ITO on graphene substrates to create high-efficiency perovskite solar cells is a realistic option. This research provides a sustainable and cost-effective method for producing high-performance perovskite solar cells by eco-friendly upcycling e-waste for ITO extraction, addressing the critical issue of e-trash management. Keywords Perovskite solar cells, CNTs, sustainable energy, energy conversion.

Electrical and Optical Characterization of Atmospheric Pressure Plasmas for the Treatment of OPV Materials

In the last years, non-equilibrium cold plasma at atmospheric pressure have led to numerous opportunities for material treatment. Depending on the gas mixtures, the electrodes configurations, the electrical waveform used to generate the discharge, or the material, a wide range of surface properties can be created. Among the plethora of applications, the organic photovoltaic (OPV) community has recently explored the use of plasma [1]. Thanks to the versatility of the cold atmospheric pressure plasmas (CAPP), all the layers used in the OPV cells could be potentially treated and modified. The use of dry atmospheric pressure processes also opens the doors to fast treatments at reduced cost compared to low pressure [2].Possible CAPP configurations for the OPV include plasma jets and dielectric barrier discharges (DBD) in volume or surface [3]. Among the different use of plasma in OPV, surface cleaning has been largely studied. For example, the removal of organic contaminants from indium tin oxide (ITO) layer have successfully been achieved with all the aforementioned configurations as well as different gas mixtures such as N2, O2, or He [4–6]. Other interesting mechanisms, such as the passivation of the electron transport layer [7], the modification of the work function [8], or for the encapsulation of the whole OPV cells [9] have been also explored.Still, whatever the material, either the metallic electrodes, the semiconductive active layer, or the dielectric substrates, a fine control of the plasma properties is necessary to ensure the good reproducibility and the stability of the process. It is hence necessary to characterize the physical regime and clarify the chemical reactions suitable to assess the good operation of the process during the material treatment.This work focuses on the use of electrical measurements and optical emission spectroscopy (OES) to retrieve key parameters from the process, like the discharge regime (Townsend vs filamentary), the capacitances of the system, or the power dissipated during the treatment [10]. In this context, this work aims at characterizing different discharge regimes for the surface treatment of thin characteristic layers employed in OPV (i.e., ITO, fluorine doped tin oxide (FTO) and zinc oxide). The influence of different electrical signals (low frequency sinusoidal voltage vs nanopulse), as well as different configurations and dielectric materials are compared. In order to link and allow to use such measurement as monitoring tools for the treatment process of materials used in OPV cells, the treated surfaces are also analyzed by SEM and contact angle. The extracted quantities from the plasma diagnostics could hence be used as a predictive tool to forecast the final properties of the treated materials and improve the processes of material treatment in OPV.[1] Mariotti et al. https://doi.org/10.1002/ppap.201500187[2] Vida et al. https://doi.org/10.37904/nanocon.2019.8646[3] Homola et al. https://doi.org/10.1016/B978-0-323-89930-7.00001-7[4] Chiang et al. https://doi.org/10.1007/s11090-010-9237-4[5] Yi et al. https://doi.org/10.1016/j.surfcoat.2003.08.011[6] Hvojnik et al. https://doi.org/10.1016/j.mssp.2021.105850[7] Polydorou et al. https://doi.org/10.1039/C6TA03594A[8] Chaney et al. https://doi.org/10.1016/S0169-4332(01)00347-6[9] Juillard et al. https://doi.org/10.1002/admi.202000293[10] Pipa et al. https://doi.org/10.3390/atoms7010014

Synthesis of sputtered self-catalytic indium tin oxide nanorods for photovoltaic application

Three-dimensional (3D) nano-structured electrode by transparent conducting oxide (TCO) is a considerable approach for increasing efficiency of optoelectronic devices. Indium tin oxide (ITO) is a potential candidate for anode applications due to its high conductivity and a high work function. Nanorods of indium tin oxide (ITONR) were grown on catalyst-free substrates at relatively low temperature by magnetron sputtering, which is free of any carrier gases and catalyst. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanorods. The reported ITONR shows photo-luminance property, making it effective for photovoltaic applications. The morphology and sheet resistance of nanorod had a significant effect on the solar cell performance. Sheet resistance of 10 Ω/□ and transparency of 83.6 % of ITONR on SCHOTT glass was achieved. The higher surface to volume ratio, superior optical and electrical properties over flat ITO layer, makes the nanorods a potential candidate for photovoltaic application.

A Transparent Photo/Electrothermal Composite Coating with Liquid-like Slippery Property for All-Day Anti-/De-Icing.

A photo/electrothermal surface can convert sunlight and electricity into heat to solve icing problems. The combination of active photo/electrothermal surfaces with passive slippery surfaces provides a highly efficient strategy for all-day anti/deicing. However, the lack of transparency remains a primary impediment to the widespread application of these anti-icing measures in photovoltaics, windshields, and other fields. Herein, we report a bilayer transparent photo/electrothermal coating with a liquid-like slippery property for all-day anti/deicing. The prepared coating exhibits ultraslippery, low ice adhesion, and enhanced stability properties through covalent grafting of polydimethylsiloxane (PDMS) brushes in a cross-linked skeleton of epoxy. Moreover, the coating demonstrates a visible transmittance of up to 77% and effectively absorbs ultraviolet and near-infrared light due to the addition of ultraviolet and infrared absorbers, resulting in a temperature increase under sun illumination. The bottom indium tin oxide layer is fabricated to provide the composite coating with electrothermal capability, so that it can achieve all-weather deicing. The coupling of photo/electrothermal and slippery properties can promote the rapid removal of grown ice in a short time. The slippery properties and their exceptional durability under mechanical, optical, and thermal conditions render the composite coatings highly promising for engineering applications.

Investigation on optical and electrical properties of multilayer ITO/AZO/ITO transparent conductive oxides

This paper examines how varying the thickness of the indium tin oxide (ITO) seed layer, ranging from 8 to 20 nm, impacts the optical, electrical, and structural properties of triple-layer transparent conductive oxide ITO/aluminum doped zinc oxide (AZO)/ITO. ITO and AZO films were deposited by DC and RF magnetron sputtering, respectively. The thickness and density of each layer were measured by X-ray reflectometry (XRR). X-ray diffraction showed that as the thickness of the ITO seed layer increased, both the average size of the crystallites and the volume of the crystalline phase in the AZO film also increased. Measurements of the electrical characteristics indicated a decrease in resistivity as the thickness of the ITO seed layer increased. This reduction is attributed to enhanced charge mobility, resulting from improved crystallinity. It has been shown that a 20-nm-thick ITO seed layer is sufficient to achieve a charge mobility comparable to that of pure ITO films. The photoluminescence spectra have shown a decrease in the concentration of the oxygen vacancies with the introduction of both the cover and seed layers of ITO. The figure of merits (FOM) of the triple-layer coatings and the optical constants of the AZO and ITO films were calculated. The results of this paper indicate that the ITO20/AZO48/ITO12 triple-layer coating possesses optimal characteristics for use in high-efficiency silicon solar cells.

Multifunctional Intelligent Metamaterial Computing System: Independent Parallel Analog Signal Processing

Analog computing based on miniaturized surfaces has gained attention for its high‐speed and low‐power mathematical operations. Building on recent advances, an anisotropic space‐time digital metasurface for parallel and programmable wave‐based mathematical operations is proposed. Using frequency conversions, our metasurface performs 1st‐order and 2nd‐order spatial differentiations, integrodifferential equations, and sharp edge detection in spatially encoded images. The anisotropic nature of the meta‐particle enables independent and simultaneous operations for two orthogonal polarizations. Reconfigurability is achieved through tunable gate biasing of an indium tin oxide layer. Illustrative examples demonstrate that the metasurface's output signals and transfer functions closely match ideal transfer functions, confirming its versatility and effectiveness. Unlike other wave‐based signal processors, the design handles wide spatial frequency bandwidths, even with high spatial frequency inputs.

Localized surface plasmon-enhanced nanorod micro-LEDs with Ag nanoparticles embedded in insulating and planarizing spin-on glass

To enhance the emission of GaN-based Micro-LEDs (μLEDs), we etched uniform nanorods (NRs) on the μLED surface and filled the nanorod gaps with spin-on glass (SOG) containing mixed Ag nanoparticles (NPs). The nanorod structure creates a conducive environment for close interaction between Ag NPs and quantum wells (QWs), facilitating the coupling of Ag NPs as localized surface plasmons (LSPs) with the QWs to enhance light emission. The SOG acts as an insulating layer between Ag NPs and NRs, preventing electron leakage, while also serving as a planarization material for the nanorod structure. This configuration allows for the fabrication of a planar Indium Tin Oxide layer without short-circuiting the nanorod structure. Compared to traditional planar Micro-LEDs, NR-μLEDs with SOG-encased Ag NPs exhibit a 50% increase in electroluminescence (EL) intensity and a 56% increase in photoluminescence (PL) intensity. This work paves the way for broader applications of LSP in μLEDs.

Optical constants and thickness gradients for light intensities in glass substrate layers and for complex electric fields in indium tin oxide (ITO) transparent conductor thin film layer, using Bode and Nyquist wavelength-dependent diagrams

Abstract The optical constants of a thin film layer of transparent conductive indium tin oxide (ITO), deposited on a thick glass substrate (G), were obtained for an ITO-G sample using a multilayer matrix method by fitting the regular transmittance and specular reflectance measurements to the collimated equations of the four-flux model, once the optical constants of the glass substrate layer had previously been obtained from a G sample of a single glass substrate layer. The accuracy of the results was validated using a feedback system called the three-extinction matching requirement, that is, obtaining the same extinction coefficients from the optical constants and from the forward and backward collimated differential equations of the four-flux model. To calculate the extinction coefficients of the glass from optical constants, the compression of the wavelength of the incident light in the glass substrate and in the thin ITO film layer was demonstrated, with a thickness less than the wavelength of incident light. The thickness gradients of the forward and backward collimated light intensities, on the glass substrate of the ITOG sample, were compared with those obtained for the single-layer G sample. Then, the thickness gradients for the complex forward and backward electric fields of the ITO thin film layer were obtained and plotted using spectral magnitude and phase Bode plots and new Nyquist plots, i.e. imaginary versus real parts, dependent on wavelength.

Maintaining Electrochemical Performance of Flexible ITO-PET Electrodes under High Strain.

Flexible electrode materials, particularly indium tin oxide (ITO)-coated polyethylene terephthalate (PET), have attracted the attention of researchers for a wide variety of applications. However, there has been limited attention to the effects of electrode flexibility during electrochemical processes. In this research article, we studied how bending commercially available ITO-PET electrodes impacts the electrodeposition process of polyaniline (PANI). Thicker ITO layers start cracking at a normalized strain of 0.10 (bending radius of 10 mm), and cracking becomes detrimental to full deposition at a normalized strain of 0.16 or higher (bending radius of 6 mm or lower). Thinner ITO layers were evaluated as electrodes in electrochemical applications; however, the higher resistance of these electrodes prevented uniform electrodeposition of PANI. In order to overcome the issues of cracking, conductive thin films and copper tape were explored as low-cost methods for electrically bridging cracks in the electrode. While conductive thin films reduced the resistance effect, copper tape was found to fully restore the original electrochemical activity as measured by chronoamperometry and enable uniform electrodeposition at a bending radius as low as 3 mm. This strategy was then demonstrated by performing electrochromic bleaching of PANI under high-strain conditions. These studies illustrate some of the limitations of ITO-PET electrodes and strategies for overcoming these limitations for future applications that require a high degree of flexibility in a transparent electrode substrate.

Effect of carbon dots on tuning molecular alignment, dielectric and electrical properties of a smectogenic cyanobiphenyl-based liquid crystal material

Here, we demonstrate the effect of dispersing organosoluble carbon dots (CDs, ∼7–8 nm) on tuning the molecular alignment, dielectric and electrical properties of smectic A (SmA) and nematic (N) mesophases of a thermotropic smectogenic LC material, 4-octyl-4′-cyanobiphenyl (8CB) in a planar anchored indium tin oxide (ITO) sample cell using polarized optical microscopy and dielectric spectroscopic techniques. The cross-polarized optical textures clearly show that the doping of CDs (concentration ⩾0.25 wt%) in planar anchored 8CB liquid crtstal (LC) led to the changing of its alignment from planar to vertical. Interestingly, such an induced vertical alignment remains stable throughout the SmA and N phases of the 8CB LC material. Moreover, the magnitude of the real dielectric permittivity is found to increase with increasing concentration of CDs and exhibits vertical alignment values for composites (⩾0.25 wt%). The observance of short axis molecular relaxation for composites (⩾0.25 wt%) without the application of bias field confirms again the induced vertical alignment. The accumulation of CDs at the substrate surface and their interaction with the alignment and ITO layers can be attributed as an important factor for such induced vertical alignment. The electrical conductivity of 8CB is observed to increase significantly with the addition of CDs (i.e. an increment of up to two orders of magnitude in composites compared to pure 8CB) and attributed to the lowering of viscosity and change in molecular alignment. We certainly believe that such tunable molecular alignment throughout the SmA and N phases of thermotropic smectogenic LC material (8CB) by dopant CDs could pave the way for their applications in flexible displays, biosensors, electro-optical memory and other tunable photonic devices.