Decrease In Optical Transmittance Research Articles

Aerosol assisted chemical vapor deposition (AACVD) synthesis of nanostructured cauliflower patterning in MWCNT doped tungsten oxide

We report nanostructured tungsten oxide (WO) cauliflowers for the first time that are fabricated onto silica glass substrate at 400 °C by aerosol assisted chemical vapor deposition using tungsten hexacarbonyl and multiwalled CNTs in toluene. The deposited films are characterized by Scanning electron microscopy, Energy dispersive x-ray spectroscopy, X-ray diffractometry, Fourier transform infrared and UV–VIS spectroscopy and four-point probe for microstructural, optical and electrical properties. Surface morphology exhibits the growth of nanocauliflowers followed by the aggregation of spherical nanoparticles with high angle grain boundaries. Structural information reveals the transformation of triclinic to tetragonal phase with preferential switching from (0 2 0) to (0 0 1) plane having signatures of W-O-W symmetric vibration between (700cm-1 and 900 cm−1, somewhat perturbed by the addition of doping. In additions, films show inconsistent variation in electrical resistivity (15–109) Ω-cm due to agglomeration of MWCNTs at grain boundaries and appearance of “nanocracks” due to ionic radii mismatch of tungsten and CNTs at higher doping ratios. Black color films present decrease in optical transmittance for range of 300–400 nm attributed to trapping sites and defects generated due to incorporation of multiwalled CNTs. The splitting of Fermi level as a result of incorporation of MWCNTs caused the increase of band gap energy in range of 3.18 eV, useful in tungsten oxide based new material system which can act as the light harvesting material and energy storage simultaneously.

Annealing temperature-dependent morphology, structure, and optical properties of well-aligned ZnO nanowire arrays

In this paper, using a facile and low-cost chemical bath deposition route, well-aligned zinc oxide (ZnO) nanowire arrays (ZNWAs) were grown on the silica glass substrate at low temperature. The as-grown ZNWAs were then annealed at different temperatures from 400 to 800 °C, their morphology, crystalline structure and optical properties were analyzed in detail. The results showed that both the average diameter and length of ZnO nanowires increased with raising annealing temperature, when annealing temperature was 600 °C, the ZnO nanowires had the best crystallization quality and minimum Urbach energy, near band edge (NBE) emission peak increased sharply. In addition, when the annealing temperature was up to 800 °C, many adjacent ZnO nanowires bonded together in the ZNWAs, a substantial increase of their lattice disorder induced by too high annealing temperature, a sharp decrease in optical transmission of the ZNWAs in the visible region was found, their Urbach energy increased dramatically and crystallization quality became poor.

The Impact of in Situ Crystallization on Oxygen Surface Exchange Kinetics of Mixed Conducting Thin Film Oxygen Electrodes

The high temperature oxygen surface exchange kinetics of mixed conducting oxides play a critical role in the efficiency of solid oxide fuel/electrolysis cells (SOCs). Recently, an in situ Optical Transmission Relaxation (OTR) approach has been applied to quantify the oxygen surface exchange coefficients (kchem ) of thin films, with the advantage of providing contact-free, in situ and continuous measurements of native surfaces. The technique relies upon the application of the Beer-Lambert law, where optical absorption is proportional to the concentration of absorbing species, e.g. oxidized Pr (~Pr4+) in PrxCe1-xO2- δ (PCO) [1 ,2 ] or oxidized Fe (~Fe4+) in SrTi1-xFexO3- δ (STF), and to the oxygen stoichiometry via electroneutrality. For example in STF, during reduction (oxygen evolution), absorbing Fe4+ is replaced by Fe3+, resulting in an increase in measured optical transmission through the STF with time, which can be described by the surface exchange-limited kinetics equation to determine kchem . [ 3 ]. As we know, the grain size and degree of crystallinity could affect the thin films’ electrical, optical and catalytic properties. In our previous work, we examined the impact of crystallinity, grain boundaries, orientation, and surface chemistry on kchem for STF (x=0.35, STF35) by preparing films of different structures by pulsed laser deposition under different conditions. We found that fast oxygen surface exchange needs both crystallinity (typically obtained at high growth temperatures) and low Sr surface concentration (typically obtained at low growth temperatures). Amorphous STF thin films were not able to exhibit optically measurable oxygen exchange, while excellent crystallinity, obtained at high growth temperatures, coexisted with high Sr segregation and therefore non-optimal kchem . However, crystallization at intermediate temperatures was used to obtain much faster surface exchange kinetics [ 4 ]. In this work, we further studied the effect of crystallization on oxygen surface exchange kinetics, by post-annealing as-grown amorphous STF35 thin films and observing the evolution of their oxygen exchange behavior in situ during crystallization. The impact of annealing temperature (500-800 °C) and time (2-100 h) on the crystallinity and microstructure was observed by scanning probe microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and in situ optical transmission changes. The consistent appearance of a significant decrease in optical transmission during heating suggested that crystallization began around 545-550 ºC. The best kchem was found for annealing at 600 ºC for 2 h. The thin film with lower (or perhaps no) crystallinity annealed at 500 °C was not able to exhibit detectable oxygen surface exchange, while higher annealing temperatures and/or times led to non-optimal kchem , which is consistent with our previous research. In order to assess whether the benefits of crystallization under mild conditions for rapid surface exchange also applied to other compositions and structures, we investigated the surface exchange kinetics during in situ crystallization of other materials, such as perovskite SrTi0.65Co0.35O3- δ (STC35), fluorite Pr0.1Ce0.9O2- δ (PCO), and Ruddlesden-Popper Sr2Ti0.65Fe0.35O4± δ (RP-STF35). Optical relaxations were observed in these materials, enabling the quantification of their kchem . For the perovskite STC35 and RP-STF35 thin films, in-situ crystallization was observed to benefit the oxygen exchange kinetics. On the other hand, for a fluorite PCO thin film, we found that it was already crystalline after deposition at 25 ºC. Therefore, the annealing process for PCO thin film did not show a positive effect on kchem . Implications for use of thin film electrodes in intermediate temperature devices will be addressed. Acknowledgements Support from WPI-I2CNER and a JSPS Kakenhi Grant-in-aid for Young Scientists (B) project number JP15K18213 (to N. H. Perry) and JSPS Fellowship (201702103) are gratefully acknowledged. Reference [1] J. J. Kim, S. R. Bishop, N. J. Thompson, D. Chen and H. L. Tuller, “Investigation of nonstoichiometry in oxide thin films by simultaneous in s itu optical absorption and chemical capacitance measurements: Pr-doped ceria, a case study”, Chemistry of Materials , 2014, 26, 1374-1379. [2] J. J. Kim, S. R. Bishop, N. J. Thompson and H. L. Tuller, “Investigation of redox kinetics by simultaneous i n s itu optical absorption relaxation and electrode impedance measurements: pr doped ceria thin films”, ECS Transactions, 57 (1) 1979-1984 (2013) [3] I. Denk, F. Noll and J. Maier, “In situ profiles of oxygen diffusion in SrTiO3: bulk behavior and boundary effects”, Journal of the American Ceramic Society , 1997, 80, 279-285. [4] T. Chen, G.F. Harrington, K. Sasaki, and N.H. Perry, “Impact of microstructure and crystallinity on surface exchange kinetics of strontium titanium iron oxide perovskite by in situ optical transmission relaxation approach”, Journal of Materials Chemistry A , 2017, 5, 23006-23019

Optical semitransparent silver nanostructured layer electrode toward semitransparent lithium ion batteries

Silver nanoparticles (AgNPs) layers have been grown by spray-pyrolysis technique by using different spray pyrolysis deposition times (tsp). AgNPs with ca. 80 nm mean diameter have been obtained for the lower tsp value, whereas as the spray-pyrolysis time value is increased, the Ag NPs diameters increased, reaching a AgNPs mean diameter of 190 nm for the highest tsp assayed value. X-ray diffraction patterns of the AgNPs layers samples exhibited a pure polycrystalline cubic silver phase, irrespective of the different tsp values. An optical visible light transmittance maximum of 60% at 550 nm has been observed for samples grown at tsp = 5 s and 10 s. For higher tsp values this optical transmittance decreases. A semitransparent lithium ion battery (tsp = 5 s) has been obtained, exhibiting an optical transmittance of about 49% at λ = 554 nm. Electrochemical measurements showed that the amount of lithium that reacted with the AgNPs layer was around 6 lithium/mol. By cycling a transparent Li/Ag-ITO single cell, good capacity retention was observed for the first ten cycles for which a high value of capacity is delivered: 706 A h kg−1.When assembling this electrode in a full semitransparent battery, the electrochemical processes resulted to be reversible and the transparency preserved.

Anodic copper oxide nanowire and nanopore arrays with mixed phase content: synthesis, characterization and optical limiting response

Thin films consisting of copper oxide nanowires (NWs) containing a mixture of copper oxide phases were formed by electrochemical anodization in de-ionized water (DI) and methanol based electrolytes. Well-defined arrays of vertical nanopores were obtained via anodization in ethylene glycol (EG)-based electrolytes. Optical absorption spectra revealed the electronic bandgap of the NWs formed in DI and methanol to be 2.50 eV, and that of nanopores formed in EG electrolytes to be 1.94 eV. The nanostructures were found to exhibit p-type conduction through Mott–Schottky analysis. The as-formed nanostructures exhibited two photon photoluminescence with lifetimes ranging between 200 and 1100 ps. They also displayed strong optical limiting in the form of a 25% decrease in optical transmission at 800 nm at a relatively low fluence of 0.1 J cm−2 and an absolute transmittance <50% over the entire range of laser fluence values used in this study. The optical transmittance decreased from 40% at an incident Ti-sapphire laser fluence of 20 mJ cm−2 to ∼9% when the fluence was increased to 700 mJ cm−2. Furthermore, the damage threshold of 0.7 J cm−2 compares favorably with advanced optical limiting materials such as gold-graphene composites and single-walled carbon nanotube composites even without further optimization of nanoscale morphology to maximize scattering. Therefore the nanostructures of mixed copper oxide films studied in this report are particularly promising as optical limiters for protecting low damage threshold (<1 J cm−2) photonic devices and are an important addition to the narrow selection of optical limiting materials that are currently available.

Gas barrier and optical properties of cellulose nanofiber coatings with dispersed TiO2 nanoparticles

Bilayer membranes for food packaging applications were prepared by depositing on polylactic acid (PLA) substrates pure cellulose nanofibers' (CNF) coatings and nanocomposite coatings made of CNF with dispersed TiO2 nanoparticles. The gas barrier properties of the bilayer membranes were studied by gas phase permeation technique using CO2, N2, D2, He and ambient air as test gases. Few micrometer thick pure and nanocomposite CNF coatings act as effective gas permeation barriers impeding the CO2, N2 and O2 transport and reducing the He and D2 transport rates by 3 orders of magnitude when compared with the PLA substrate. Gas transport through the coatings obeys the solution-diffusion mechanism: D2 permeation process shows activation energy values of 44±6kJ/mol and 40±6kJ/mol in the pure and nanocomposite CNF coating, respectively. The addition of the TiO2 nanoparticles reduces the penetrant diffusivity by increasing the tortuosity of the penetrant migration path but does not affect the gas barrier performances. UV–Vis spectroscopy analyses show that the optical transparency of the PLA support is slightly decreased by the CNF coating: at 600nm the optical transmittance decreases, in fact, from 95% to 91%. TiO2 nanoparticles strongly absorb UV radiation and slightly reduce the PLA transparency in the optical range due to light scattering effects.

Reduced electrical performance of Zn enriched ZnTe nanoinclusion semiconductors thin films for buffer layer in solar cells

Closed space sublimation (CSS) technique was employed to deposit thin films of zinc telluride (ZnTe) on a glass substrate under high vacuum. Two sets of ZnTe thin films and Zn enriched ZnTe thin films were prepared for comparative study. The enrichment for Zn onto the as-deposited ZnTe thin films was done by the novel manner of layer by layer deposition with subsequent annealing. X-ray diffraction (XRD) studies revealed before and after the enrichment of Zn the preferred orientation is [1 1 1] having cubic phase. The lattice constant was found to be increased and the crystallite size decreased 28 nm to 24 nm after the enrichment of Zn. A morphological study was carried out through a scanning electron microscope (SEM). For Zn enriched samples the average grain size is smaller as compared to ZnTe thin films. The local compositions of Zn and Te were confirmed by energy dispersive x-rays (EDX) from 51 atomic % of as-deposited ZnTe thin films to 68 atomic % in Zn enriched ZnTe thin films. The Zn enriched samples have a slight decrease in optical transmission in UV–VIS–NIR range as compared to the as-deposited ZnTe thin films. Due to the deposition of Zn there is a very small change in optical band gap energy. A four-probe technique was used to study electrical properties of as-deposited and Zn-enriched ZnTe thin films. These results shows that the as-deposited samples had the resistivity of 106 Ω · cm. For Zn enrichment samples resistivity increases from 106 Ω · cm to 108 Ω · cm, which shows that Zn-enriched samples are not suitable for back contact of II–VI solar cells. X-rays photoelectron spectroscopy (XPS) was used to confirm the elemental compositions and its bonding strength before and after the enrichment of Zn.

Annealing of Sputtered InSb Thin Film for III-V Semiconductor Devices Applications

Abstract: In this paper, the effect of annealing temperature on Indium antimonide (InSb) thin films has been studied. It is proved that the increase in annealing temperature enhances the crystallinity of the InSb thin film. Thin films of InSb have been deposited on silicon and glass substrates by RF sputtering, then vacuum-annealed at 150, 300, 390 and 450 ⁰C. Differential scanning calorimeter (DSC) analysis indicates that InSb thin film crystallizes at 389 ⁰C or above. X-ray diffraction (XRD) results show peaks at (111), (220) and (311) planes, which indicates the formation of crystalline grains. Fourier transform infrared (FTIR) spectroscopy indicates the decrease of optical transmittance upon increasing the annealing temperature, the analysis shows that InSb thin films have bandgaps between 0.233 and 0.241 e.v.

ZnO crystal as a potential damage-recoverable window material for fusion reactors

Hydrothermal-grown bulk zinc oxide (ZnO) single crystals are investigated before and after 1-keV hydrogen-ion and deuterium-ion plasma irradiation. A decrease in optical transmittance, red-shifting of ultraviolet (UV) emission peaks, and shortening of UV emission lifetimes are observed from the bulk crystals immediately after irradiation. The results are attributed to the radiation-induced defects formed by hydrogen implantation. Although these defects immediately affect the optical properties of the single crystals, the optical transmittances and photoluminescence emissions recover days after irradiation. Our observations show the potential properties of a bulk ZnO single crystal as a damage-recoverable window material in high-flux-radiation environments such as those of fusion reactors.

Surface topographical and structural analysis of Ag+-implanted polymethylmethacrylate

Specimens of polymethylmethacrylate (PMMA) were implanted with 400-keV Ag+ ions at different ion fluences ranging from 1×1014 to 5×1015ions/cm2 using a 400-kV NEC ion implanter. The surface topographical features of the implanted PMMA were investigated by a confocal microscope. Modifications in the structural properties of the implanted specimens were analyzed in comparison with pristine PMMA by X-ray diffraction (XRD) and Raman spectroscopy. UV–Visible spectroscopy was applied to determine the effects of ion implantation on optical transmittance of the implanted PMMA. The confocal microscopic images revealed the formation of hillock-like microstructures along the ion track on the implanted PMMA surface. The increase in ion fluence led to more nucleation of hillocks. The XRD pattern confirmed the amorphous nature of pristine and implanted PMMA, while the Raman studies justified the transformation of Ag+-implanted PMMA into amorphous carbon at the ion fluence of ⩾5×1014ions/cm2. Moreover, the decrease in optical transmittance of PMMA is associated with the formation of hillocks and ion-induced structural modifications after implantation.

Influence of annealing temperature on In2O3 properties grown by an ultrasonic spray CVD process

This article discusses influence of the annealing temperature on the structural, optical and electrical properties of indium oxide thin films which are prepared on glass substrate heated at 150°C by ultrasonic spray technique using indium chloride as precursor solution. The deposited samples annealed at 300°C and 500°C for 1h. Structural analysis of these films suggest that the films are polycrystalline with a preferred grain orientation along the (222) plane, and the crystalline state of these films improve with the increase in the annealing temperature from 300°C to 500°C. The optical band gap is varied in the range of 3.64–3.73ev. UV–vis spectroscopy show that the average transmittance is about 85% in the visible region, and the optical transmittance decrease with the increase of the annealing temperature. The electrical resistivity decreases from 80Ωcm to 9.8×10−3Ωcm with the increase of the annealing temperature from 300°C to 500°C.

Growth and characterization of nonpolar (10-10) ZnO transparent conductive oxide on semipolar (11–22) GaN-based light-emitting diodes

We have grown thin films of nonpolar m-plane (10-10) ZnO on a semipolar (11–22) GaN template by atomic layer deposition (ALD) at low growth temperatures (<200 °C). The surface morphology of the ZnO film is found to be an arrowhead-like structure, which is a typical surface structure of the semipolar (11–22) GaN films. On increasing the growth temperature of the ZnO films, the concentration and mobility of the charge carriers in the ZnO film are increased. However, the optical transmittance decreases with an increase in the growth temperature. Based on these results, we have fabricated semipolar (11–22) GaN-based light-emitting diodes (LEDs) with nonpolar m-plane ZnO film as a transparent conductive oxide (TCO) to improve the light extraction efficiency. In spite of a decrease in the optical transmittance, the operation voltage of semipolar (11–22) GaN-based LEDs is found to decrease with an increase in the growth temperature, which might be due to the improvements in the electrical properties and current spreading effect, resulting in an increase in the optical output power.

Nano-Welding of Ag Nanowires Using Rapid Thermal Annealing for Transparent Conductive Films.

Ag nanowire (NW) films obtained by the spraying the Ag NWs on the substrates were nano-welded by rapid thermal annealing (RTA) process and the effect of RTA process on the change of sheet resistance and optical transmittance of the Ag NW films was investigated. The increased number of Ag NW sprays on the substrate decreased the sheet resistance but also decreased the optical transmittance. By the annealing for 60 sec in a nitrogen environment to 225-250 degrees C, the sheet resistance of Ag NW film could be decreased to about 50%, even though it was accompanied by the slight decrease of optical transmittance less than 5%. The decrease of sheet resistance was related to the nano-welding of the Ag NW junctions and the slight decrease of optical transmittance was related local melting of the Ag NWs and spreading on the substrate surface. Through the nano-welding by RTA process, the Ag NW film with the sheet resistance of -20 Ω/sq. and the optical transmittance of 93% could be obtained.

Characteristics of the Mg-Doped Cr-Deficient CuCr0.95Mg0.02O2 Thin Films Prepared by Using Pulsed Laser Deposition.

2 at% Mg doped thin films of delafossite CuCrO2 and Cr-deficient CuCr0.97O2 were prepared by pulsed laser deposition. The films were grown on c-sapphire single crystal substrates at a range of substrate temperatures, and the effects of the processing parameters on thin film properties were examined. The crystallinity improved with increasing substrate temperature and Mg-doping. The substitution of Mg in the CuCrO2 and Cr-deficient CuCr0.97O2 thin films increased the electrical conductivity significantly with a slight decrease in optical transmittance. By introducing Mg-doping to Cr-deficient CuCr0.97O2 thin films, a CuCr0.95Mg0.02O2 thin film with an electrical conductivity of 29.63 S/cm and a mean optical transmittance of 60% was fabricated.

Optical and morphological investigation of aluminium and nickel oxide composite films deposited by spray pyrolysis method as a basis of solar thermal absorber

Applications of alumina and nickel oxide in various fields specially in solar energy conversion technology encouraged us to study physical properties of such materials. Hence after the deposition of the thin films on glass substrate by spray pyrolysis, using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectrophotometry, various physical properties were investigated. Different optical quantities such as optical band gap, refractive index, extinction coefficient, dielectric constants, volume and surface energy loss functions and optical conductivity were determined. Within this paper for different nickel to aluminium ratio (from 20/80 to 80/20 ratio) at specific substrate temperatures (300°C), decrease of optical transmittance with nickel content was notable. Using the transmittance data, other optical quantities were achieved by a numerical approximation method. We also observed an increase in the volume energy loss (VELF) more than the surface energy loss (SELF) and simultaneously a decrease trend prevailed according to nickel amount. On the basic of the XRD results, the amorphous phase changed by the presence of more nickel and according to SEM, more obvious nanosized spherical grains at higher nickel ratios can be observed.

Effects of PMN/PT ratio on optical and electro-optic properties of PLMNT transparent ceramics

Lanthanum modified lead magnesium niobate-lead titanate (PLMNT) transparent ceramics with composition near morphotropic phase boundary (MPB) was fabricated by a columbite precursor method with a hot-press sintering technique. The effects of PMN/PT ratio and La content on dielectric, ferroelectric and optical properties as well as the electro-optic (EO) effect of PLMNT transparent ceramics were investigated systematically. XRD patterns show pure perovskite phase of ceramics samples. Increasing PT content from 22% to 28% increases the dielectric constant and decreases the diffusivity coefficient. Meanwhile, P–E hysteresis loop gradually change from “slim” to “square”, accompanied with significant increase of Ps, Ec and Pr. Obvious decrease in optical transmittance and significant increase in EO coefficient was observed. Those observations are ascribed to the decreasing amount of polar nanodomains in PLMNT ceramics. With increasing PT content, the transition of nanodomains into macrodomains correspondingly enlarge the domain size. The largest quadratic EO coefficient achieved is 19.9×10−16 (m/V)2 for the fabricated PLMNT-3.2/72/28 transparent ceramics.

Effect of substrate temperature on structural, morphological and optical properties of deposited Al/ZnO films

Al-doped ZnO (Al/ZnO) thin film is a promising alternative to an ITO electrode in solar cell applications due to its low price, non-toxicity and other promising properties. In this paper, Al/ZnO thin films at different substrate temperatures were deposited on glass substrates as transparent conducting (TCO) films by DC magnetron sputtering. The effect of substrate temperature on the structural, morphological and optical properties of Al/ZnO films was investigated. X-ray diffraction (XRD) analysis suggests that crystal structure characteristics of synthesized thin films depend on the substrate temperature. The structure growth and variation in surface roughness with increasing substrate temperature are revealed by scanning electron microscope (SEM) micrographs and atomic force microscopy (AFM) analyses. Thicknesses of the deposited films were also examined by surface profiler. Moreover, obtained results from optical transmission patterns revealed that with the increasing substrate temperature, optical transmittance decreases.

Large‐Scale Fabrication of Pseudocapacitive Glass Windows that Combine Electrochromism and Energy Storage

AbstractMultifunctional glass windows that combine energy storage and electrochromism have been obtained by facile thermal evaporation and electrodeposition methods. For example, WO3 films that had been deposited on fluorine‐doped tin oxide (FTO) glass exhibited a high specific capacitance of 639.8 F g−1. Their color changed from transparent to deep blue with an abrupt decrease in optical transmittance from 91.3 % to 15.1 % at a wavelength of 633 nm when a voltage of −0.6 V (vs. Ag/AgCl) was applied, demonstrating its excellent energy‐storage and electrochromism properties. As a second example, a polyaniline‐based pseudocapacitive glass was also developed, and its color can change from green to blue. A large‐scale pseudocapacitive WO3‐based glass window (15×15 cm2) was fabricated as a prototype. Such smart pseudocapacitive glass windows show great potential in functioning as electrochromic windows and concurrently powering electronic devices, such as mobile phones or laptops.

Large-scale fabrication of pseudocapacitive glass windows that combine electrochromism and energy storage.

Multifunctional glass windows that combine energy storage and electrochromism have been obtained by facile thermal evaporation and electrodeposition methods. For example, WO3 films that had been deposited on fluorine-doped tin oxide (FTO) glass exhibited a high specific capacitance of 639.8 F g(-1). Their color changed from transparent to deep blue with an abrupt decrease in optical transmittance from 91.3% to 15.1% at a wavelength of 633 nm when a voltage of -0.6 V (vs. Ag/AgCl) was applied, demonstrating its excellent energy-storage and electrochromism properties. As a second example, a polyaniline-based pseudocapacitive glass was also developed, and its color can change from green to blue. A large-scale pseudocapacitive WO3-based glass window (15×15 cm(2)) was fabricated as a prototype. Such smart pseudocapacitive glass windows show great potential in functioning as electrochromic windows and concurrently powering electronic devices, such as mobile phones or laptops.

Nonlinear optical properties of polyvinylcarbazole composites with graphene

The study has focused on polyvinylcarbazole (PVK) composites with graphene. It has been shown that there is a noticeable nonadditive shoulder on the long-wavelength edge of the optical absorption of PVK in these samples, which can be attributed to the formation of a charge-transfer complex between PVK as a donor and graphene as an acceptor. The formation of the complex causes a significant nonlinear optical effect in the PVK/graphene composite. The revealed increase in both the nonlinearity coefficient with increasing laser intensity and the cross section with increasing incident energy density is due to the formation of the graphene−· radical anion, an additional species contributing to nonlinear absorption, with an increase in the radiation energy density. Nonlinear optical properties of PVK composites with graphene isolated from a solution in tetrachloroethane after 1.5-h centrifugation (sample 1) have been considered. It has been suggested that a significant decrease in optical transmission of laser radiation by the composite TOA = 0.4 at an energy density at focus of 502 J/cm2 is due to the formation of the PVK/graphene charge-transfer complex responsible for the nonadditive shoulder on the long-wavelength optical absorption edge of PVK. During photoexcitation of graphene in the PVK/graphene composites at a laser wavelength of 1064 nm, mobile holes are generated in PVK, indicating the formation of graphene−· radical anions as a result of charge transfer from PVK to photoexcited graphene. The observed increase in both β with an increase in the laser radiation intensity and the cross section (σexc — σ0) with an increase in the incident energy density may be due to either the contribution of nonlinear transitions (S0 → S2, S0 → S1 → S2, T1 → T2) or the formation of the additional species, the graphene-· radical anions, participating in nonlinear absorption by increasing the energy density at the focus (Ffoc, J/cm2).