Poly N-vinylcarbazole Research Articles

Optical properties of a tunable microcavity/microsphere polymeric composite

The combination of a microcavity and a microsphere has been proposed in this work to manipulate light in terms of emission wavelength and propagation direction. A microcavity with a layer of molecular photoswitch between two one-dimensional photonic crystals of polyvinyl carbazole and cellulose acetate has been designed. To tune the microcavity, the molecular photoswitch has been excited taking into account its cyclization upon irradiation at 313[Formula: see text]nm and its cycloreversion at 450[Formula: see text]nm. In this way, the emission peak of the microcavity switches from 508.5[Formula: see text]nm to 525[Formula: see text]nm. A polystyrene microsphere with a radius of 1[Formula: see text][Formula: see text]m is placed near the microcavity. With the detector at an angle of 8°, the emission at 525[Formula: see text]nm is 1.73 times higher with respect to the emission at 508.5[Formula: see text]nm, while at 10.8°, the emission at 508.5[Formula: see text]nm is 1.45 times higher with respect to the emission at 525[Formula: see text]nm. The value of these findings is that they offer the experimentalists a ready means to compare the optical data of these types of composites with theory.

Transition metal oxide-polymer composite supported PtPd/PNVC-WO3 nano-catalyst: Multifaceted functional behavior boosting the performance of ethanol oxidation kinetics

This investigation involves synthesis of PtPd catalyst nano-particles supported on tungsten oxide (WO3) and poly-N vinyl carbazole (PNVC) composite for validation in ethanol oxidation reaction. The tungsten oxide acquires excellent functional property by hydrogen spill over phenomenon that facilitates hydrogen tungsten bronze formation while conducting polymer enhances the charge transfer ability within the direct ethanol fuel cell framework. The catalyst nano-particles are found to be in the size range 3–5 nm, revealed from structure and morphology studies. Electrochemical characterizations derive output power density of ∼54 mW cm−2 and mass activity ∼1.9 A/mgPt, in terms of specific current density for ethanol oxidation. Ion chromatographic analysis quantifies the reaction intermediates, acetate and carbonate to the extent of 396 and 280 ppm using 1 M ethanol solution. Self designed composite nano-structures of PtPd/PNVC-WO3 with reduced Pt share provide astounding opportunity for the catalytic reaction to gear up to the complete oxidation kinetics.

An insight into the role of titanium oxide nanofiller on the structural, optical, electrical, and dielectric characteristics of PS/PVK composite

Nanocomposite films made of polystyrene (PS) and polyvinyl carbazole (PVK) and filled with varying quantities of titanium oxide (TiO2) nanoparticles (NPs) were prepared using the solution casting process. The TiO2 NPs’ impact on the pure PS/PVK blend’s structural, optical, and conductive properties was investigated and explained. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) measurements indicate that the synthesized TiO2 NPs’ size ranges between 12 and 32 nm and has a tetragonal anatase phase. The XRD scans also indicate that the PS/PVK filling with TiO2 NPs decreases the nanocomposite crystallinity. Fourier transform infrared (FTIR) analysis shows the main distinctive absorption peaks of PS and PVK, whose intensities changed randomly after filling. Moreover, the highest TiO2 NPs content showed a new peak at 449 cm−1. The UV/visible measurements showed that the optical energy gaps for the direct and indirect permitted transitions decreased as the TiO2 NPs content increased. Using impedance spectroscopy at room temperature, the AC electrical conductivity of the PS/PVK mixture containing TiO2 NPs was investigated over a broad frequency range from 10−1 to 107 Hz. It has been shown that the frequency dependence of AC electrical conductivity obeys Jonscher’s rule, and the increase of TiO2 NPs concentration in the blend induces the formation of a percolating network within the composite. It has also been shown that the composite’s dielectric loss and constant increase with nanoparticle concentration.

Synthesis and Micro hardness Studies of Polymer Nanocomposites of ZnS with PVK

The synthesis and microhardness studies of ZnS with PVK ((Poly N-Vinylcarbazole) nanocomposites are presented. The thin films was form with different loding of ZnS in PVK using chemical rout method and characterized them SEM (Scanning Electron microscope), XRD (X-ray diffraction), AFM (Atomic Force Microscope) and study their mechanical properties. XRD shows ZnS have cubic nanocrystals structure, with particle size about 3 to 12 nm. Broadening of line shows the formation of amorphous compound. The SEM, AFM images reveal clustering of particles within 10 to 100 nm. These three studies reveal the particle size respectively increases with ZnS loading in the PVK. The microhardness study on pure PVK and ZnS with PVK nanocomposites helps us to understand the modification in properties due to inter- and intra- molecular interactions. It is seen that ZnS with PVK nanocomposites exhibit lower value of microhardness as compare to pure PVK and minimum for highest loading (50% ZnS) of ZnS in PVK. For each ZnS loading at first, the microhardness increases with the load and after that, beyond particular load, it obtain a saturated value, so it can be say the samples are fully strain-hardened at this load. The micro hardness also corresponds to frictional force. With increasing load the coefficient of friction decreases and the frictional force increases linearly with the increasing load. Therefore, the change in Vickers hardness number (Hv) is curvilinear with load.

Luminescence study of ZnS/PVK nanocomposites

Sulphide-based luminescence materials have attracted more curiosity for their extensive applications in electro and photoluminescence devices. One of the sulphides, such as zinc sulphide (ZnS), is a favourable material for phosphor growth in various bands for visible emission. The composition of the polymer matrix with ZnS demonstrates its special functions and stabilizes the nanoparticles. We have used chemical methods for the preparation of ZnS/PVK nanocomposites and reported their synthesis, photoluminescence (PL), and electroluminescence (EL) studies. The samples were analyzed through SEM (Scanning Electron Microscope), AFM (Atomic Force Microscope), and XRD (X-ray Diffraction). The XRD study shows the formation of ZnS nanocrystals with a cubic crystal structure, having a size between 3 and 12 nm and the broadening of peaks shows the formation of an amorphous compound. The AFM and SEM show clusters of particles in the range of a few tens to a few hundred nm. The results from all three studies show an increase in the size of particles with the ZnS loading in PVK (poly N-vinylcarbazole). The PL of a PVK sample excited at 400 nm shows a single PL peak at 451 nm and covers the spectral range from 400 to 600 nm. ZnS/PVK samples excited by 370 nm, give a PL peak due to PVK near 450 nm and when excited by 425 nm, the PL peak is found near 470 nm due to defect-related transitions in ZnS. In both cases, PL intensity increases with increasing ZnS loading in PVK. This may be because of interfacial charge transfer and radiative recombination. The EL studies show that corresponding to the applied voltage, the brightness is increased. The EL emission starts at a lower threshold voltage with a higher loading of ZnS in PVK and at a higher threshold voltage for higher frequencies. EL intensity of the composites increases with increasing ZnS loading in PVK. The voltage-current curve shows the linear relationship between voltage and current that is ohmic in nature. The frequency of applied voltage increases as impedance decreases.

Photonic band-edge assisted enhanced nonlinear absorption of carbon encapsulated gold nanostructures in polymeric multilayers

Integration of nonlinear optical materials in nanophotonic structures offers unprecedented opportunities to tailor the light-matter interaction, resulting in tunable optical responses. Periodic dielectric structures are particularly the desired optical platform to incorporate nonlinear materials to enhance their weak nonlinearity for practical applications. In this work, we report the giant enhancement in the nonlinear absorption of a 1-D polymer photonic crystal containing gold-carbon (Au@C) core–shell structure. The Au@C nanostructures synthesized by pulsed laser ablation technique were dispersed in spin-coated alternate layers of photonic crystal comprised of polyvinyl carbazole and cellulose acetate. The long-wavelength photonic band-edge of the polymeric Bragg mirror was designed at 532 nm to enhance the non-resonant nonlinear absorption of the core–shell nanostructure. The resultant nonlinearity is ascribed to slow light propagation at the band-edges and consequent local field confinement of optical pulses. Angle-dependent tunability of photonic band-edge effects and nonlinear transmission characteristics were analyzed experimentally and correlated with numerical simulations. These findings open up new ways to implement cost-effective, highly tunable and low input threshold all-optical devices.

Tunable cavity modes in diarylethene-based photo-switchable polymeric microcavities and study of the light-pulse propagation through the microcavities

Light responsive devices employing molecular photo-switches are interesting for displays and dynamic light filtering. In this work, polymeric microcavities embedding a layer of photochromic compound have been studied by means of the transfer matrix method. Different polymers, such as poly vinyl carbazole, poly styrene and cellulose acetate, have been used. A microcavity that includes random one-dimensional photonic structures sandwiching the photochromic layer has also been studied. Propagation of light pulses through the microcavities has been analysed.

Composite PVK/SLGO As Matrix for MALDI-TOF MS Detection of Small Molecules in Dual-Ion Mode.

Currently, most matrices developed for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) for small-molecule detection are only suitable for the positive or negative ion mode and not the dual-ion mode, except for carbon-based nanomaterials. The lone-pair electrons on the N atom in poly n-vinylcarbazole (PVK) can serve as a Lewis base with strong electron-donation effects, which is favorable for negative ion mode detection. The surface of single-layer graphene oxide (SLGO) contains many oxygen atoms in carboxyl and hydroxyl groups that act as Lewis acids and thereby provides favorable protonation sites for positive ion mode detection. In this study, composite PVK/SLGO was prepared by combining the advantages of amorphous PVK and SLGO. PVK/SLGO was tested as a novel matrix for positive- and negative-ion-mode MALDI-TOF MS for the analysis of amino acids, nucleic acid bases, environmental endocrine disruptors, antibiotics, and various small molecules. PVK/SLGO was compared with PVK, SLGO, and commercially available matrices of 9-aminoacridine (9-AA) and α-cyano-4-hydroxycinnamic acid (CHCA). The PVK/SLGO matrix was demonstrated to be suitable for the positive and negative ion modes, exhibiting high signal intensity and detection sensitivity without background interference. The limits of detection of the aforementioned molecules ranged from 0.1 to 0.0001 and 0.01 to 0.0001 mg/mL in the positive and negative ion modes, respectively. The quantitative determination of enrofloxacin in milk was realized using an internal standard method with a linear range of 0.0001-0.1 mg/mL (R 2 = 0.9991). Furthermore, the PVK/SLGO matrix exhibited high salt tolerance (up to 1000 mmol/L) and stability over 28 consecutive days. Studies regarding its ionization mechanism revealed that the good performance originates from the combined materials acting synergistically. This study provides a foundation for developing bimodal composite matrices and further expands the scope of PVK/SLGO applications.

Organic Photoelectric Materials and Organic Photoelectric Devices Based on Smart Image Sensors

With the development of the times in recent years, people’s requirements for vision are no longer limited to the original foundation. As the core of research in this field, organic electroluminescence has paid great attention to the research points in the application of organic optoelectronic materials and devices in the world. From the relevant scientific research results in recent years, for example, organic light-emitting diodes can be used in flat-panel displays and solid-state lighting, organic photovoltaic cells can be used as a clean and renewable energy source to effectively alleviate the current energy needs of society, and organic storage, sensors, and so on show great promise for application. It can be seen that the research of organic optoelectronic materials and their devices will be the core hot spot of future new energy research. In the past, traditional organic optoelectronic materials are updated through the regulation strategy of covalent modification of the molecular structure. In recent years, new effective methods have been obtained to regulate the properties of excited states through physical stimulation (such as mechanical force, temperature, electric field, and magnetic field). The type of research experiment in this paper is based on the current hot smart image sensor, with the addition of organic complexes of mononuclear metal platinum and iridium metal and the organic optoelectronic device in the form of host and guest doping. The experimental results show that using PVK without energy transfer, polyvinyl carbazole (PVK) had been widely used as blue luminescent material and hole transport layer in electroluminescent device research. Simple mononuclear platinum and iridium metal complexes cannot obtain white light. For OPV devices, by selecting the correct solvent to control the bulk heterojunction, it exhibits better photovoltaic performance. Solvents play an important role in phase separation. In organic solar cells (OPV) consisting of an electron donor (D) and an acceptor (A), optimizing the D-A interface produces efficient charge separation, effectively separating excitons at the D-A interface and forming continuous electron and hole transport channels, and effective charge transport between electrodes plays a positive role.

Highly efficient blue quantum-dot light-emitting diodes based on a mixed composite of a carbazole donor and a triazine acceptor as the hole transport layer.

Solution-processed thermally activated delayed fluorescence (TADF) exciplexes were employed as the hole transport layer (HTL) of blue quantum dot (QD) light-emitting diodes (QLEDs) by blending polymer donors of poly(N-vinylcarbazole) (PVK) with small molecular acceptors of 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T). As a result, the PVK:T2T HTL can harvest holes and electrons leaking from the QD active layer to form exciplex excitons and then this harvested exciton energy can be effectively transferred to the adjacent QD emitters through the Förster resonance energy-transfer process. Furthermore, the TADF exciplexes can enhance the hole mobility of the HTL due to the charge transfer process from the PVK donor to the T2T acceptor under an external electric field. The maximum current efficiency (CE) and external quantum efficiency (EQE) of the fabricated blue ZnCdS/ZnS core/shell QLEDs increase from 4.14 cd A-1 and 7.33% for the PVK HTL to 7.73 cd A-1 and 13.66% for the PVK:(5 wt%)T2T HTL, respectively. Our results demonstrate that the TADF exciplex HTL would be a facile strategy to design high-performance blue QLEDs.

Versatile Pendant Polymer for Selective Charge Carrier Transport via Controlling the Supramolecular Self-Assembly.

Polyvinyl carbazole (P0)-based pendant polymers were synthesized by modifying carbazole motifs with pyrene derivatives (P1 and P4) to manipulate the bandgap and frontier orbital energy levels. To establish the electronic properties of pendant polymers according to structural differences, the polymers were utilized as additional hole transport layers in planar-type perovskite solar cells and organic photovoltaic cells. When P4 with thiophene-pyrene pendant was used as hole transport layer, all device parameters, except open-circuit voltage, were significantly improved in comparison with P0 and P1 (conjugated with t-butyl pyrene derivatives). Since P4 had more electrically conductive thiophene units than benzene units with fewer alkyl groups, the supramolecular assembly of P4 was found to be more favorable in electronic devices. Furthermore, devices with P4 demonstrated lower dark current than others, which could potentially be useful for charge carrier transport and sensitive photo detecting devices.

Light‐Emitting Electrochemical Cells with Polymer‐Blended InP/ZnSeS Quantum Dot Active Layer

AbstractA light‐emitting electrochemical cell (LEC) is an innovative device with a simple structure wherein a mixture of a luminophore and an electrolyte is sandwiched between electrodes. Here, LECs are presented which contain an active layer composed of green‐emitting InP/ZnSeS quantum dots (QDs) blended with polyvinyl carbozole p‐type polymer semiconductors and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid (IL). The blending of QDs with polymer semiconductors increases the density of holes reaching the QDs; this, in turn, leads to luminescence from QDs, which is unachievable without the presence of polyvinyl carbazole semiconductor. Moreover, the deposition of a zinc oxide nanoparticle layer onto the QD–polymer–IL active layer increases the density of electrons reaching the QDs. The composition of these materials is varied systematically for balancing the injection rates of electron versus hole into the QDs. A luminance of ≈632 cd m−2 and an efficiency of >1.3 cd A−1 are achieved.

Efficient and Stable MAPbI3-Based Perovskite Solar Cells Using Polyvinylcarbazole Passivation.

Hybrid perovskite solar cells attract a great deal of attention due to the feasibility of their low-cost production and their demonstration of impressive power conversion efficiencies (PCEs) exceeding 25%. However, the insufficient intrinsic stability of lead halides under light soaking and thermal stress impedes practical implementation of this technology. Herein, we show that the photothermal aging of a widely used perovskite light absorber such as MAPbI3 can be suppressed significantly by using polyvinylcarbazole (PVC) as a stabilizing agent. By applying a few complementary methods, we reveal that the PVC additive leads to passivation of defects in the absorber material. Introducing an optimal content of PVC into MAPbI3 delivers a PCE of 18.7% in combination with a significantly improved solar cell operational lifetime: devices retained ∼70% of the initial efficiency after light soaking for 1500 h, whereas the control samples without PVC degraded almost completely under the same conditions.

Multi-level resistive write-once-read-many memory device based on CdSe/ZnS quantum dots and ZnO nanoparticles

ABSTRACT Multi-level three-state resistive memory devices were fabricated using CdSe/ZnS quantum dots (QDs) and ZnO nanoparticles (NPs). Poly-vinyl carbazole (PVK) was added to the synthesized CdSe/ZnS QDs with a core/shell structure to form a stronger charge storage layer in the QDs. The use of PVK enables the design-stage control of the state current and write voltage, along with improvement of the on/off ratio. All thin films were fabricated by the solution spin coating method. Additional quantum wells can be produced using ZnO NPs, which enables the multistate functionality. We optimized the process conditions with respect to PVK and ZnO NPs, and confirmed that the PVK concentration was optimized at 2.5 wt%. In addition, the optimized memory device had an on/off ratio of 1.43 × 106 at 0.5 V, the write voltages were 2.2 V and 3.5 V, and the current values in the 0, 1 and 2 states were 4.7 × 10−9 mA, 2.1 × 10−5 mA, 1.0 × 10−1 mA, respectively. The fabricated device demonstrated high stability and reliability through 20 repeat cycles, and displayed a retention time of 80 h.

Optimized trade-off between electroluminescent stability and efficiency in solution-processed WOLEDs adopting functional iridium(III) complexes with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety

Employing complimentary color phosphorescent emitters of the well-known FIrpic and new unsymmetrical orange emitter Ir-POB with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety, solution-processed white organic lighting-emitting diodes (WOLEDs) had been fabricated to cope with the variation of EL spectra at different working voltage through excitation of both FIrpic and Ir-POB with the same mechanism in the device. Through constructing a thin exciton formation zone by the energy level layout between host 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and 1,3,5-tris-(N-(phenyl)-benzimidazole)-benzene (TPBi), both FIrpic and Ir-POB in the single emission layer can be excited by energy-transfer mechanism to bring stable white EL spectra in wide range of driving voltages with small CIE coordinate variation of Δx = 0.0044 and Δy = 0.0197. Furthermore, in order to overcome the disadvantage associated with energy-transfer mechanism, both FIrpic and Ir-POB have been excited by direct charge-trapping mechanism in WOLEDs by judiciously controlling the energy level layout between phosphorescent emitters and co-hosts polyvinyl carbazole (PVK) and 1,3-bis(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene (OXD-7). The concerned WOLEDs not only maintain stable white EL in even wider driving voltage rang with CIE coordinate variation of Δx = 0.0078 and Δy = 0.0053, but also furnish much higher EL efficiencies of maximum external quantum efficiency (ηext) of 22.4%, a maximum current efficiency (ηL) of 58.4 cd A−1 and a maximum power efficiency (ηP) of 41.3 lm W−1. Hence, by unifying excitation mechanism of the phosphorescent emitters, optimized trade-off between white EL stability and high EL efficiencies have been successfully achieved. Definitely, these results can provide crucial information for developing WOLEDs with high performances.

Multilayer plasmonic photonic structures embedding photochromic molecules or optical gain molecules

We design photonic structures embedding different functional molecular systems of photochromic switching and lasing. We study the light absorption of two photochromic molecules and of 4,4'-bis[(N-carbazole)styryl]biphenyl (BSB-Cz) with density functional theory. For the photochromic diarylethene we derivate the refractive index with Kramers-Kronig relations and we design multilayer photonic structures alternating diarylethene with either poly vinyl carbazole or fluorine indium co-doped cadmium oxide (FICO) nanoparticlebased layers. For BSB-Cz we design a one-dimensional photonic crystal alternating BSB-Cz layers with $SiO_{2}$ layers and a microcavity embedding BSB-Cz between indium tin oxide (ITO) / FICO nanoparticle-based multilayers.

Theoretical study on the effect of spacer groups on the nonlinear optical properties of polyvinyl carbazole molecular fragments

In this paper, polyvinyl carbazole fragments with side-hung chromogenic groups were used as the parent. The relationship between the structure and the properties of NLO was studied by changing the type of spacer groups on chromogenic groups with density functional theory (DFT). The results show that all designed systems have significant second-order NLO response. The first hyperpolarizability (β0) of the system has the following regularity (taking PBE0 algorithm as an example): the β0 value of the system is related to the type of electron-donating and electron-withdrawing spacer group (X).The β0 value of electron-donating spacer group is larger than that of electron-withdrawing spacer, and the β0 value of the molecule is independent of the size of the spacer group. When the spacer group is methyl, the value of β0 (168.1 × 10−30 esu) is the largest in tested electron-donating group. When the spacer group is an electron-withdrawing group, the value of β0 is related to electron-withdrawing ability, and the value of β0 is inversely proportional to the electron-withdrawing ability of the spacer group.

Dual and Multi-Emission Hybrid Micelles Realized through Coordination-Driven Self-Assembly.

Building novel functional nanomaterials with a polymer is one of the most dynamic research fields at present. Here, three amphiphilic block copolymers of 8-hydroxyquinoline derivative motifs (MQ) with excellent coordination function were synthesized by Reversible Addition-Fragmentation Chain Transfer Polymerization (RAFT) polymerization. The coordination micelles were prepared through the self-assembly process, which the MQ motifs were dispersed in the hydrophobic polystyrene (PSt) blocks and hydrophilic Poly(N-isopropylacrylamide (PNIPAM)) blocks, respectively. The dual-emission micelles including the intrinsic red light emission of quantum dots (QDs) and the coordination green light emission of Zn2+-MQ complexes were built by introducing the CdSe/ZnS and CdTe/ZnS QDs in the core and shell precisely in the coordination micelles through the coordination-driven self-assembly process. Furthermore, based on the principle of three primary colors that produce white light emission, vinyl carbazole units (Polyvinyl Carbazole, PVK) with blue light emission were introduced into the hydrophilic PNIPAM blocks to construct the white light micelles that possess special multi-emission properties in which the intrinsic red light emission of QDs, the coordination green light of Zn2+-MQ complexes, and the blue light emission of PVK were synergized. The dual and multi-emission hybrid micelles have great application prospects in ratiometric fluorescent probes and biomarkers.

Studies on CdSe/PVK nanocomposites films for electroluminescent display applications

In the present work, the thin films of CdSe/PVK nanocomposites with various concentration of CdSe have been synthesized by chemical route. Polyvinyl carbazole (PVK) was used as a stabilizer as well as host matrix to prevent agglomeration of nanoparticles. The synthesized CdSe/PVK films were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV–Visible absorption spectra. The crystalline size was calculated from the XRD while FESEM images confirm the surface morphology of CdSe/PVK nanocomposites. CdSe nanocrystals have hexagonal phase and size increases with increasing CdSe content, Single PL peak at 498 nm for all the samples is caused by luminescence centres or surface/defect states. The EL spectra are quite broad as compared to PL spectra and the peaks are obtained at nearly same wavelength. The EL peak intensity increases slightly and shifts towards red by increasing concentration of CdSe in polymer matrix.

Opto-electrically and electro-optically controllable diaphragm aperture in a poly(N-vinylcarbazole) film-coated tandem-90°-twisted nematic liquid crystal cell

The opto-electrically and electro-optically controllable diaphragm aperture in a poly(N-vinylcarbazole) (PVK) film-coated tandem-90°-twisted nematic liquid crystal (TNLC) cell is investigated. The tandem-90°-TNLC cell assembled by two common 45°-TNLC cells can be adopted for incident linearly polarized lights at any linear polarization direction. The variations of diaphragm aperture made by a PVK film-coated tandem-90°-TNLC cell are demonstrated opto-electrically and electro-optically. The differences in the degree of linear polarization between the tandem-90°-TNLC and single-90°-TNLC cells for demonstrating diaphragm apertures are investigated. The dynamic transmittance, related to orientation of LCs resulting from the built-in electric fields induced by the diffused positive and negative ions in LC bulk, the induced electric fields generated by the diffused ions in LC bulk and conductive PVK films, and the ion-moving induced force, of the PVK film-coated tandem-90°-TNLC cell is studied, and the possible mechanism based on dynamic distribution of ions (impurities) in LC bulk is also proposed. The proposed mechanism of the dynamic transmittance phenomenon can be a useful reference to the developments of other PVK film-coated LC cells. Moreover, the PVK film-coated tandem-90°-TNLC cell can be considered a controllable diaphragm aperture shutter if the above ion-induced issues are overcome.