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The bulk-heterojunction (BHJ) system that uses a π -conjugated polymer as an electron donor, and a fullerene derivative as an electron acceptor, is widely used in organic solar cells (OSCs) to facilitate efficient charge separation and extraction. However, the conventional BHJ system still suffers from unwanted phase segregation caused by the existence of significant differences in surface energy between the two BHJ components and the charge extraction layer during film formation. In the present work, we demonstrate a sophisticated control of fast film-growth kinetics that can be used to achieve a uniform distribution of donor and acceptor materials in the BHJ layer of OSCs without undesirable phase separation. Our approach involves depositing the BHJ solution onto a spinning substrate, thus inducing rapid evaporation of the solvent during BHJ film formation. The fast-growth process prevents the fullerene derivative from migrating toward the charge extraction layer, thereby enabling a homogeneous distribution of the fullerene derivative within the BHJ film. The OSCs based on the fast-growth BHJ thin film are found to exhibit substantial increases in JSC, fill factor, and a PCE up to 11.27 mA/cm2, 66%, and 4.68%, respectively; this last value represents a remarkable 17% increase in PCE compared to that of conventional OSCs. [ABSTRACT FROM AUTHOR]

Hybrid molecules based on C60 fullerene and strained polycyclic hydrocarbons have been synthesized for the first time using the Bingel–Hirsch reaction. Thin films based on the synthesized hybrid compounds have been obtained and their surface morphology has been studied. Organic field-effect transistors have been fabricated based on thin films of the С60 fullerene adducts bearing fragments of strained polycyclic hydrocarbons. Current-voltage characteristics of the transistors have been measured and the mobility of the charge carriers has been calculated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photooxidation processes of PCDTBT polymer thin film were tuned by additives. • UV–vis absorption photobleaching degree correlates with paramagnetic defects kinetics. • 2% admixture of fluorinated carbon nanotubes inhibits photooxidation of PCDTBT. The influence of the additives to the thin film of the semiconducting polymer PCDTBT on the kinetics of its photooxidation in air was revealed through changes in the UV–vis absorption spectra and the EPR spectra of the paramagnetic defects. These defects appeared in the initial stage of the PCDTBT photooxidation, and the kinetics of their generation and decay reflected the impact of the additives on PCDTBT stability. While a small amount of PCBM and beta-carotene resulted in the accelerated photooxidation, the addition of fluorinated carbon nanotubes stabilized PCDTBT. [ABSTRACT FROM AUTHOR]

We report weak ferromagnetism in fullerene thin films at the temperature of 2K-300K by 600 keV carbon ion irradiation. The fullerene thin films were irradiated with 600 keV carbon ions. The thin films of fullerene exhibit a significant and stable weak ferromagnetic ordering at room temperature after irradiation with variable ion fluence. Fullerene has exhibited a maximum magnetic ordering with carbon ion beam irradiation at the ion fluence of 0.03 pC/µm2 in the present experiment. The observed ferromagnetic ordering diminishes upon irradiation with higher fluences due to a higher degree of damage, which is confirmed by the Glancing angle x-ray diffraction and Raman analysis results. The saturation magnetic moments rapidly reduce, as we increase the fluence. Computational simulations have been performed to determine the approximate distance between defects and their relation with observed ferromagnetism, utilizing simulation studies from Stopping Range of Ions in Matter (SRIM) codes for the present experimental conditions. The correlation between theoretical as well as experimental studies reveals, that the fullerene thin films, get amorphized with the fluence of 0.03 pC/µm2 and beyond for 600 keV carbon ion irradiation. We have applied moderate ion flux to avoid the possibility of annealing during the carbon ion irradiation. We report our findings with systematic analysis in the present manuscript. [ABSTRACT FROM AUTHOR]

This introduction of the recursion formula for HT ht was a major step towards the fast adoption of the K-K consistent B-spline formulation in SE data analysis. From Equation (16) we see that a convex combination of two lower-order shifted basis function HT ht and HT ht gives the value of the higher-order basis function HT ht . Keywords: data analysis; dielectric function; optical modeling; parameterization; spectroscopic ellipsometry; spline functions EN data analysis dielectric function optical modeling parameterization spectroscopic ellipsometry spline functions 93 115 23 08/09/22 20220501 NES 220501 1 Introduction Spectroscopic ellipsometry (SE) is a non-destructive technique for fast and informative characterization of surfaces, thin films and multilayer structures including not only the film thicknesses but also the optical functions (yet, as of old, often referred to as optical constants) as well as surface and interfacial roughness [[1]], [[2]], [[3]]. Moreover, changing the control point for particular basis function HT ht affects the spline curve I S i ( I x i ) only on interval [ I t i SB I j i sb , I t i SB I j i + I p i +1 sb ], i.e., locally. [Extracted from the article]

Featured Application: Solar thermal collectors with nanofluids. In this work, the performance of a low-temperature solar collector (LTSC) is evaluated, using carbon nanoparticles in water as working fluid. The nanoparticles used are crystallized fullerenes, with a red parameter of 1.42 nm ± 0.5 nm, with different volume fractions in water. The thickness of the carbon film was approximately 140 to 520 nm. The study is divided into three parts: modeling and simulation of an LTSC, low-cost production and characterization of nanoparticles, and thermal evaluation of the LTSC. For the study, fullerenes were produced by microwave synthesis from a terpenoid resin (Camphor) and the nanoparticles were characterized by scanning electron microscopy (SEM) and High-Resolution Transmission (HRTEM). Tests were carried out with different volumetric flow rates, 0.0111 LT/s, 0.0166 LT/s and 0.0194 L/s, and two volumetric concentrations, 0.035% and 0.063%. The results obtained from the fullerene nanofluid showed an improvement in the thermophysical properties compared to the properties of water. The performance results showed that the efficiency increases up to 47.2% compared to that of water, with a volume fraction of 0.063%, and a flow rate of 0.0194 LT/s. [ABSTRACT FROM AUTHOR]

C60 and C60-ZnO thin films were synthesized by spray pyrolysis method, and structural, chemical, optical and self-cleaning characterizations of this nanocomposite were performed before and after plasma treatment. The C60 thin film has a very wide peak in the range of 2θ = 15–35°, which indicates the amorphous structure of this film. After plasma treatment, fullerene peaks appear at angles of 2θ = 13.94, 17°. Fullerene peaks in the C60-ZnO and C60 thin films are similar and are seen exactly at the same angles. The location of zinc oxide peaks did not change before and after plasma treatment. The presence of fullerene peaks in the studied thin films after plasma treatment indicates that the crystallographic quality of C60 and ZnO-C60 thin films has improved. FESEM image of fullerene thin films before and after plasma treatment shows that fullerene nanoparticles are almost spherical. After plasma treatment, the particle size is reduced, and all particles are below 50 nm with spherical shape. FESEM images of C60-ZnO thin film after plasma treatment show both fullerene and zinc oxide particles become smaller and the particles have a uniform distribution. The results of FTIR chemical analysis in thin film samples show the chemical bonds of the nanocomposite before and after plasma treatment. In AFM images, the surface of the C60 thin film is smooth and uniform before plasma compared to after plasma processing. Also, in C60-ZnO composite, the grain size after plasma treatment is much larger than before plasma treatment. The contact angle of the thin films indicates that the composite samples become hydrophobic after plasma processing. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) are renewable, sustainable and biocompatible nanomaterials, which have gained great attention in last years for their potentialities in several fields of application. With their polyelectrolyte behaviour, sulphated CNCs are suitable to produce multilayered architectures with cationic molecules. In this work, we have investigated the ability of anionic CNCs to assist the two-dimensional organization of two cationic fulleropyrrolidines at the air/water interface, leading to hybrid Langmuir-Schäfer films with improved (photo)electrical properties. We demonstrated that CNCs interact with the fulleropyrrolidines at the air/water interface, favouring the assembly of organized hybrid C 60 /CNC films. The transfer efficiency of Langmuir layers and the morphological regularity of supported films proved to be influenced by the extent of positive charge on the fullerene counterpart. Interestingly, the electrochemical characterization of hybrid films revealed that sulphated nanocellulose strongly improves the electrical properties of organized fullerene layers, by increasing their conductivity and favouring the hydrogen evolution reaction. Moreover, the well-established C 60 photoactivity proved to be enhanced by CNCs, as demonstrated by the higher intensity of photocurrents. This outstanding nanocellulose impact on fullerene film electrical properties paves the way to the development of more performing C 60 -based electrochemical devices, able to better exploit the unique properties of carbon nanostructures. Image 1 [ABSTRACT FROM AUTHOR]

In the present work, an efficient route has been further explored to achieve the batch synthesis of inorganic fullerene (IF)-WS2 nanoparticles, and the self-lubricating film is conveniently prepared by coating these nanoparticles on the surface of metal substrates. The as-synthesized IF-WS2 nanoparticles have a closed hollow structure with an average particle size of about 50 nm and are evenly distributed in the self-lubricating film. Further friction tests show that the film has excellent friction properties, with its lowest friction coefficient of approximately 0.008, which can be mainly attributed to the unique hollow cage structure and a smaller particle size of the IF-WS2 nanoparticles. [ABSTRACT FROM AUTHOR]

We have probed the structural and magnetic properties of a ferromagnetic/organic interface constituted by a polycrystalline Co layer deposited on a fullerene thin film through resonant soft X-ray reflectivity measurements. The fitting analysis of the reflectivity indicates the formation of a sharp interface with limited intermixing and a null remanent magnetization in a ~1 nm thick region of the Co film at the interface with C60. This information contributes to elucidate the role of organic–inorganic interfaces in the charge and spin transport inside organic spintronic devices. [ABSTRACT FROM AUTHOR]

Bi-functional nanocomposite thin films of fullerene C60 and C70 containing Au NPs were synthesized using thermal co-evaporation method. Different atomic concentrations of Au metal varying from 5 to 35 at.% was chosen to get the Au NPs with different sizes in fullerene matrix. The thickness of films and metal concentration is confirmed by Rutherford backscattering spectroscopy (RBS). UV-visible spectrum shows the excitation of SPR band in all samples except for the lowest metal concentration which is ~ 5 at.% and SPR is red shifted with increasing concentration of Au. The shift in SPR position with increasing metal concentration for both Au-C60 and Au-C70 is nearly linear. X-ray diffraction spectroscopy indicates the formation of bigger size particles with increasing metal concentration in both the cases of Au-C60 and Au-C70, which is further confirmed by transmission electron microscopy results. Au-C60 and Au-C70 (could) be interesting nanocomposites for surface-enhanced Raman scattering studies. [ABSTRACT FROM AUTHOR]

Hydrogenated fullerenelike carbon (H-FLC) films, with high hardness of 41.7 ± 1.4 GPa and elastic recovery of ∼75.1%, have been uniformly deposited at low temperature by pulse direct current plasma enhanced chemical vapor deposition (pulse DC PECVD). The superior mechanical properties of the H-FLC films are attributed to the unique curvature and interconnection of graphitic basal planes. We propose the fullerenelike structures are formed in the far nonequilibrium pulse plasma environment and stabilized in the sequential fast quenching process. It is expected that the facile deposition of H-FLC films will promote the large-scale low-temperature preparation of engineering protective films for industrial applications. [ABSTRACT FROM AUTHOR]

Using first-principles density functional theory and nonequilibrium Green’s function formalism, we investigate the effect of the indices of crystal plane of electrodes on the electronic transport properties of molecular devices by taking C20 fullerene molecule as conductor component and semi-infinite Au(111)/(100) as electrodes. The results show that the transport behaviors through molecular devices are closely related to the crystallographic orientation of electrodes. Negative differential resistance (NDR) in the current-voltage curve can be observed for the Au(100) electrode case but cannot be observed for the Au(111) case. A mechanism for the NDR phenomenon is proposed. [ABSTRACT FROM AUTHOR]

Nanocomposite thin films of fullerene C60 containing Ag nanoparticles (NPs) were synthesized by thermal codeposition. The surface plasmon resonance (SPR) band of the nanocomposite film was observed in the region 450–550 nm, showing a large redshift with increasing metal concentration. This is explained by the Maxwell–Garnett effective medium theory considering the absorbing nature of fullerene C60. The C60–Ag nanocomposite thin film with lowest Ag concentration was annealed at increasing temperatures in neutral atmosphere. The SPR band showed first a small redshift after annealing at small temperature then progressive blueshift at higher temperature. This behavior of SPR is explained by the increased particle–particle interaction due to the compaction of the fullerene C60 film upon annealing at low temperature and the transformation of fullerene C60 matrix into amorphous carbon at higher temperature. Rutherford backscattering spectrometry and transmission electron microscopy were used to quantify Ag metal content and the microstructural evolution of Ag NPs in the nanocomposite films, respectively. Thermal induced structural transformations of fullerene C60 molecules of host matrix were investigated by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The efficiency of polymer based bulk heterojunction (BHJ) solar cells mainly depends on the film morphology of the absorption layer and the interface properties between the stacked layers. A comparative study using atomic force microscopy (AFM) and optical in situ thin film drying measurements is performed. The strong impact of distinct drying scenarios on the polymer:fullerene BHJ layer morphology is investigated by AFM. The AFM images show a systematic dependency of structure sizes at the surface on drying kinetics. In addition thin film optical measurements for the determination of thin film drying kinetics and parameters are performed using a dedicated experimental setup. The data are used as the input for a quantitative simulation of the drying process. The film thickness decreases linearly during drying while the solvent mass fraction decreases moderately over a wide range until it drops rapidly. Subsequently the remaining solvent fraction evaporates considerably slower. Our work gives a fundamental understanding of the film formation kinetics and prerequisites for the systematic optimization of the film morphology in solution processed organic photovoltaic devices. [ABSTRACT FROM AUTHOR]

Films comprising predominantly novel isomers of C60 [=C60(nIPR)] have been generated by low energy ion beam deposition of vibronically excited C60+ onto graphite followed by selective sublimation of C60(Ih) from the deposited isomer mixture. The incident ions were generated by electron impact ionization/fragmentation of sublimed C70. Images of the C60(nIPR) films obtained by applying atomic force microscopy show aggregates, which we attribute to covalently interlinked C60(nIPR) units. The covalent bonds are inferred from the significantly higher thermal stability of the C60(nIPR) films compared to the C60(Ih) van der Waals solid–as measured by thermal desorption with mass spectrometric detection of the C60 mass channel (the only desorbable species). In contrast to the characteristic doublet structure of the occupied valence band in the ultraviolet photoelectron spectrum of pure C60(Ih), the valence band of C60(nIPR) films exhibits a triplet feature with the additional peak occurring at a binding energy of ∼2.6 eV. This is an indicator of the electronic modifications induced by intermolecular bonding. C60(nIPR) films exhibit a narrower band gap than found for C60(Ih). They also have significantly different chemical reactivity toward incorporation of thermal energy deuterium atoms. In order to model the experimental photoelectron spectra, various covalently linked oligomers of #1809C60(C2v), the second most stable conventional 60-atom fullerene cage, were calculated by means of the density functional theory. These spectral predictions together with analogous previous observations on related fullerene solids such as C58 lead us to infer that C60(nIPR) films consist of fullerene cage isomers containing one or more adjacent pentagon pairs, which mediate covalent cage-cage interconnection. [ABSTRACT FROM AUTHOR]

This article reports on the formation and electronic characteristics of conducting carbon nanowires produced by swift heavy ion irradiation of a fullerene thin film. This study shows that it is possible to create arrays of carbon nanowires, which are perfectly parallel to each other and perpendicular to the substrate. As-deposited fullerene films exhibit poor field emission characteristics with breakdown fields as high as 51 V/μm, whereas low dose ion irradiated fullerene film produces a threshold field as low as 9 V/μm. The present approach of making conducting carbon nanowires by ion irradiation for potential field emitters and large area applications is also discussed. [ABSTRACT FROM AUTHOR]

In this study we report on field effect mobilities of charge carriers in materials used in polymer photovoltaics. The field effect mobilities of charge carriers in polymer and fullerene films and in various blend compositions were investigated for the effects of tempering. Contact resistances were considered for more accurate mobility estimations. The field effect mobilities of holes in films of the conjugated polymer poly(3-hexylthiophene) (P3HT) were found to be in the 10-3 cm2/V s range and the field effect mobilities of electrons in films of the methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) were found to be in the order of 10-2 cm2/V s. The concentration of PCBM was then varied in P3HT:PCBM blends, and blend compositions with PCBM contents of 0%, 33%, 40%, 50%, 60%, 67%, and 100% weight percents were measured before and after tempering. Electron mobilities were not detected in untempered blend compositions with PCBM content lower than 67% PCBM. Tempering led to a large increase in the electron mobility in the blends, and electron mobilities were detected in all tempered blends with PCBM content above 40%. Electron and hole field effect mobilities were found to be roughly balanced in the 10-3 cm2/V s range for the tempered blend with 67% PCBM content. [ABSTRACT FROM AUTHOR]

Three primary colors, red, green, and blue have been obtained from a single-emission layer organic light-emitting diode (OLED) through optical design using a half-wavelength all-metal-cavity device. Fullerene is used as an electron transport layer to further enhance the electrical performance of the cavity device and the optical tuning of the cavity OLED. This fullerene layer results in a ∼2 V driving voltage reduction and a ∼20% increase in power efficiency, as compared with traditional cavity OLED with Alq as the electron transport layer. The emissive spectra for the cavity OLEDs are well predicted by the Fabry–Perot cavity theory. The spectral narrowing and intensity enhancement at the resonance wavelength have been observed and are explained by the redistribution of optical-mode density inside the microcavity. Schemes to tune the emissive color by varying the cavity length through variations of indium tin oxide thickness, hole transport layer thickness, and electron transport thickness, individually or collectively, have been proposed and demonstrated. [ABSTRACT FROM AUTHOR]

Copper metal embedded fullerene C60 thin films are deposited on various substrates via resistive heating co evaporation technique. Rutherford back scattering simulated spectrum confirms the thickness and composition of thin film to be ~ 32 nm and ~ 18 at%, respectively. The deposited thin films are irradiated by 120 MeV Ag ion beam for different fluences within the range, from 1 × 1012 to 3 × 1013 ions/cm2. UV–vis absorption spectroscopy study reveals the appearance of surface plasmon resonance (SPR) band in pristine thin film at ~ 622 nm; this phenomenon is ascribed to the presence of copper nanoparticles in C60 matrix. The SPR band intensity increases with rising fluences, which is suggestive of the growth of Cu nanoparticles. Growth of Cu nanoparticles is further confirmed by transmission electron microscopic (TEM) and X-ray diffraction (XRD) study. Whereas the conversion of C60 into amorphous carbon (a-C) is confirmed by Raman spectroscopy, XRD results of pristine Cu–C60 thin film record the presence of Cu2O within the nanocomposite thin film. However, both X-ray photoelectron spectroscopy (XPS) and XRD studies on irradiated thin film samples authenticate the growth of Cu metal nanoparticles with concurrent removal of oxygen. [ABSTRACT FROM AUTHOR]

Abstract Even though [60]fullerene has excellent electrochemical stability and strong electron affinity, it is barely made into dense-packed film through electrophoresis method in electronic devices. But with the help of the long hydrophobic arms of tetra-n-octyl ammonium bromide in toluene solution, electrophoresis deposition was successfully used as an easy way to fabricate high quality [60]fullerene film on ITO glass substrate. When the composition and thickness of the film were confirmed by IR, XPS and SEM, the resulted film was used as the middle functional layer of RRAM device. After the IV spectra test of memory devices with different thickness of [60]fullerene layer, it was found that the memory character changed from Flash to WORM when the film thickness evolved from 200 nm to 400 nm. This is the first example to study memory performance of uniform C60 film manufactured by the electrophoresis deposition. Graphical abstract The continuous and dense-packed fullerene film with tunable thickness has been successfully fabricated using an easy electrophoresis deposition method and the corresponding RRAM devices show Flash-to-WORM performance transform when the film thickness evolves from 200 nm to 400 nm. Image 1 Highlights • Dense [60]fullerene molecules stacking induced by electrophoresis deposition. • Tunable thickness of flat electron-acceptor film. • Memory performance evolving from Flash to WORM. • Conductive-Filament related switching. [ABSTRACT FROM AUTHOR]

Time dependence of the electronic structure of an electron-beam (EB) irradiated C60 film (20–30 nm thick) has been examined using in situ high-resolution ultraviolet photoelectron spectroscopy. It is found that the electronic states of the C60 film have been changed continuously from an insulator (pristine C60 films) to a semiconductor and finally to a metal as EB-irradiation time increased. This can be explained by the increase in polymerization degree of a C60 polymer with a given cross-linked structure derived from the general Stone–Wales rearrangement from [Beu et al.,Phys. Rev. B 72, 155416 (2005)]. In addition, this finding suggests that the electronic properties of the C60 film can be controlled only in the EB-irradiated region by varying the irradiation time, which is interesting when applied to electronic devices. [ABSTRACT FROM AUTHOR]

Abstract All-polymer solar cells (All-PSCs) have attracted a lot of attention in the recent years due to broad absorption spectra, adjustable chemical structures, high morphological stability, better donor-acceptor compatibility and better mechanical durability. This review summarizes the recent development of perylene diimides (PDI)-based electron acceptors used in all-PSCs because these polymers are promising candidates. The photovoltaic performances of non-fullerene polymer acceptors were compared, and the structure-performance relationship was discussed when the same donor material was used. Highlights • Perylene diimides-based (PDI) n-type copolymers are promising electron-acceptor. • D-A alternating copolymers based on PDI is the most promising kind. • Constructing fused-PDI benefit the photovoltaic performance. • Good morphology should be maintained while enhance the electron mobility. [ABSTRACT FROM AUTHOR]

Abstract Plasmonic nanocomposite thin film containing Cu metal nanoparticles in fullerene C 60 matrix is developed by thermal co-evaporation method on glass substrate. In order to excite the surface plasmon resonance (SPR), thermal annealing is performed from 100 °C to 400 °C on as-deposited thin film in an inert atmosphere (continuous flow of Ar gas) for 30 min. SPR is successfully generated at ∼694 nm for the film annealed at a temperature of 300 °C which is further blue shifted at ∼684 nm at a temperature of 400 °C. The film thickness and Cu metal atomic concentration is found to be ∼70 nm and ∼27 at.%, respectively using Rutherford Backscattering Spectroscopy. Raman spectroscopy is used to identify the structural changes occurring in fullerene C 60 matrix with thermal annealing. The transformation of fullerene C 60 into amorphous carbon is observed with increasing temperature. Transmission electron microscopy is used to confirm the growth of Cu nanoparticles with increasing temperature and particle size is found to be 27.9 nm for the film annealed at 400 °C. The modifications in surface morphology of annealed samples are studied by field emission electron microscope (FE-SEM) and atomic force microscope (AFM). The absence of Copper oxide in the annealed samples is confirmed by X-ray photoelectron spectroscopy. Current vs. voltage measurements are performed to quantify the increased conductivity of annealed samples. Highlights • Increase in the size of cupper nanoparticles occurs as a result of thermal annealing. • Generation and blue shifting of SPR at higher temperatures of thermal annealing. • Resistance decreases with increasing the temperature of thermal annealing. [ABSTRACT FROM AUTHOR]

The increasing need of fullerenes due to its interesting properties makes it a unique molecule of the current research field. The replacement of fullerene C60 by C70 in various applications makes us to feel more intended towards the knowledge of its structural and optical behaviour under various perturbations. In the present study, the stability of fullerenes (C60 and C70) under low energy ion irradiation is investigated. Both C60 and C70 fullerene thin films were grown on glass substrate and bombarded with 2.4 MeV Ar ions at different fluences ranging from 1 × 1013 to 3 × 1016 ions/cm2. The surface morphology and topology of these films were studied by scanning electron microscopy and atomic force microscopy. The microscopic analysis shows the increase in roughness at low fluence and then roughness decreases at high fluences. At the highest fluence, the roughness of both C60 and C70 becomes equal. Various spectroscopic analysis conducted on irradiated fullerene C60 and C70 thin films show that the bandgap decreases with the increase in fluence. In case of C70 bandgap decreases to 1.6 eV which gives more allowed HOMO-LUMO transitions as compared to fullerene C60. This decrease in bandgap tends to increase the conductivity of the fullerene molecule, hence I-V measurements were performed which shows the decrease in the resistivity of both the fullerene thin films. Raman spectrum reveals the transformation of ball shaped fullerenes into amorphous carbon at higher fluences. The different vibrations in the fullerene molecule are also studied by FTIR spectroscopy. These characteristic traits of both the fullerene are studied giving the idea of the local structure and optical behaviour of the molecule as a matrix component in the metal-matrix nanocomposites. [ABSTRACT FROM AUTHOR]

Electrospray (ES) has emerged as an attractive approach to fabricate thin-film organic photovoltaic devices. However, the morphological properties and their implication to electrical characteristics of polymer:fullerene blends deposited by this method have not been clearly understood yet. In order to uncover the interplay of nanoscale morphology and electrical properties of ES-deposited films, both the residues of single droplets and thin films from the overlapping of multiple droplets were investigated by various characterization techniques. The surface morphology was demonstrated in details by the optical microscope (OM) and atom force microscope (AFM). The ordering structures and aggregation of the polymer were identified by the Raman and UV–vis spectroscopic investigations. The spatially distribution map of the P3HT aggregation states was analyzed by fitting the C˭C mode of P3HT with Lorentzian functions. The conductive atomic force microscopy (C-AFM) was used to quantify local currents and reveal the correlation between the nanostructure and charge-transport mobility. Both surface morphology and aggregation of the P3HT were found to strongly depend on the overlapping boundaries formed by the dry residues of individual droplets. More P3HT aggregation present at the boundaries. However, boundaries also show significantly higher charge-transport resistance thus lower current. Thin films deposited with less droplet evaporation exhibit more homogenous morphology, more uniform phase segregation, and consequently higher charge mobility. [ABSTRACT FROM AUTHOR]

ABSTRACT: Optical properties of polymer/fullerene blend films upon thermal annealing are investigated by spectroscopic ellipsometry and described consistently within an optical model of the blend film. The optical model developed in this work treats both components, polymer and fullerene, as mixtures of reference materials, that is, their optically ordered and disordered phase. Then, the polymer/fullerene blend layer is also described as a mixture of these two components. In this manner, we extend an existing optical model, which accounts for the optical order within the polymer phases, on cases where the optically ordered PCBM phase occurs, too. Determination of the dielectric functions of all four reference materials allows for a unique quantitative characterization of a polymer/fullerene blend film by assigning to it thickness and the polymer to fullerene volume fraction of its layers as well as corresponding volume fractions of theirs optically ordered and disordered polymer and fullerene phases. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1094–1100 [ABSTRACT FROM AUTHOR]

The plasmon-enhanced photoluminescence of fullerene C60 thin film has been studied to reveal the dependence of the magnitude of plasmonic field in coupled nanosystem monolayer of gold nanoparticles - fullerene C60film - aluminum film on the thickness of the fullerene spacer in the range of 10-95 nm. The non-monotonic dependence of the photoluminescence enhancement factor with minimum at the fullerene film thickness of 50 nm has been observed. Such dependence has been explained as the result of excitation of the propagating surface plasmon polaritons in aluminum film by the near field of localized surface plasmons of gold nanoparticles. The excitation of polaritons leads to additional radiative damping of plasmonic oscillations in gold nanoparticles that causes the decrease of the enhancement factor of the intensity of fullerene photoluminescence. Fifty nanometers is revealed to be the spacer thickness at which the most effective excitation of surface plasmon polaritons occurs. [ABSTRACT FROM AUTHOR]

The absorption spectra of C60 fullerene thin (from submonolayer to 5-6 monolayers) films deposited on different substrates have been studied. It has been shown that the spectra of the submonolayer and thick (more than 100 monolayers) films virtually coincide. The behavior of fullerene on the surface of different polymers can be judged from changes in the absorption spectra. [ABSTRACT FROM AUTHOR]

Metal matrix composites have a diverse range of applications. We have probed local structural modifications taking fullerene C 70 as a model matrix material. In this study, thin films of fullerene C 70 were grown on polished silicon and quartz substrates by resistive heating of fullerene C 70 . In order to understand local structural changes, these semi-crystalline films were irradiated with 120 keV N + ions at different fluences ranging from 1 × 10 13 to 3 × 10 16 ions.cm −2 . Microscopic analysis shows an increase in topological roughness up to a fluence of 1 × 10 15 ions.cm −2 and then a decrease. The size of the particles decreases with increase in the fluence. Various spectroscopic analyses conducted on differently irradiated fullerene C 70 films show that the bandgap decreases with the increase in the fluence which will increase the conductivity of the irradiated thin films. These results are proved by I-V measurements showing the decrease in the resistivity at higher fluences. Therefore, this characteristic trait makes fullerene C 70 to be used as a prominent matrix component in the composites. Raman spectroscopic investigations reveal that C 70 is completely transformed into amorphous carbon at a fluence of 3 × 10 16 ions.cm −2 . Different vibrational modes in FT-IR are also reported in the present work. [ABSTRACT FROM AUTHOR]

This study presents the comparative modifications in optical, structural and morphological properties of fullerene C 70 thin film induced by swift heavy ion irradiation and thermal annealing. Fullerene C 70 thin films are prepared by resistive heating method on quartz substrates. One set of the films are irradiated with 125 MeV Au ions at different fluences varying from 1×10 12 to 3×10 13 ions/cm 2 and second set of the films are annealed at temperatures varying from 50 to 350 ̊C for 30 minutes. The UV-visible spectroscopy and Raman spectroscopy are performed on pristine, irradiated and annealed films to investigate the modification in optical and structural properties after irradiation and annealing. UV-visible spectra show that the optical band gap of fullerene C 70 film decrease with increasing fluence and temperature. The experiment using Raman scattering exhibits the transformation of fullerene C 70 into amorphous carbon at higher fluences and higher temperatures as well. This transformation is evidenced by the presence of D and G bands of amorphous carbon in irradiated and annealed films. Atomic force microscopy is performed to observe the variation in surface roughness of films variation with irradiation and temperature. Swift ion irradiation induces the cylindrical zone so called “ion track” made of amorphous materials with in the fullerene C 70 thin films. The damage cross-section and radius of cylindrical zone is calculated to be 2.8 ×10 -13 cm 2 and 3.0 nm respectively using the kinetics of damage of fullerene C 70 . [ABSTRACT FROM AUTHOR]

Fullerene-based bi-functional nanocomposite thin film (Ag nanoparticles embedded in fullerene C matrix) is synthesized by thermal co-deposition method. Thermal stability of Ag-C nanocomposite is investigated by annealing the nanocomposite thin film at different temperatures from 80 to 350 °C for 30 min. Optical and structural properties of nanocomposite thin film with respect to high temperature are studied by UV-visible spectroscopy and x-ray diffraction, respectively. Transmission electron microscopy is performed to observe the temperature-dependent size evolution of Ag nanoparticles in fullerene C matrix. A large growth of Ag nanoparticles is observed with temperature especially above 200 °C due to enhanced diffusion of Ag in fullerene C at higher temperature and Ostwald ripening. The properties of metal-fullerene nanocomposite is not significantly affected up to a temperature of 150 °C. With a further increase in temperature, a major blue shift of ~ 33 nm in SPR wavelength is seen at a temperature of 300 °C due to the thermal induced structural transformation of fullerene C matrix into amorphous carbon. A very large-sized Ag nanoparticle with a wide size distribution varying from 27.8 ± 0.6 to 330.0 ± 4.5 nm is seen at 350 °C and due to which, a red shift of ~ 16 nm is obtained at this temperature. This study throws light on the thermal stability of the devices based on metal-fullerene bi-functional nanocomposite. [ABSTRACT FROM AUTHOR]

In this work, we report the fullerene thin films incorporated with a bis(perfluorophenyl) azide based photo-crosslinker. We show that introducing the photo-crosslinker into the fullerene films (LT-S9079 from Lumtec) significantly increases electrical conductivity after photo-crosslinking. We used X-ray diffraction (XRD) measurements to confirm that the crosslinking of LT-S9079 produces more ordered structure, showing that the photo-crosslinker can be a good bridge material for charge carrier transport after crosslinking. This result shows that it can be used in complicated and highly integrated optoelectronic semiconductor devices particularly those require orthogonal processes. [ABSTRACT FROM PUBLISHER]

The morphologies of C 60 and C 70 fullerene films vacuum-deposited onto graphite at various deposition rates and grown at several temperatures were investigated using atomic force microscopy. These fullerene films on graphite are model systems of physisorption of organic molecules that likely exhibit little chemical interaction with the graphite's surface. The morphologies of C 60 and C 70 films grown on graphite can be understood well from growth models previously reported. Comparison of the morphological phase diagrams obtained for C 60 and C 70 indicate that the diffusion properties of the adsorbed molecule are key in determining the morphology of the obtained film. The low diffusion rate of C 70 resulted in various film morphologies for all deposition conditions tested. Also, the obtained phase diagrams can be understood by the results of fractal dimension analysis on the C 60 and C 70 islands. The fundamental understanding of film growth obtained using these ideal physisorption systems will aid in understanding film growth by other molecular adsorption systems. [ABSTRACT FROM AUTHOR]

The relation between the nanostructure and the mechanical properties of Nb x -CoCrCuFeNi high entropy alloy thin films was explored. With increasing Nb concentration (0 to 24 at.% Nb), a transition from a single phase face-centered cubic solid solution to an amorphous phase is observed. At intermediary Nb fractions (5 to 15 at.% Nb) a nanocomposite structure is formed that consists of nanosized crystallites embedded in an amorphous matrix. The nanocomposite structure leads to an increase in hardness beyond the Hall-Petch breakdown. The shear and Young's moduli decrease with increasing Nb concentration, which is beneficial for the alloy ductility. [ABSTRACT FROM AUTHOR]

The analysis of organic materials such as phenyl-C61-butyric acid methyl ester (PC 61 BM) by depth profiling is typically fraught with difficulty due to the fragile nature of the sample. In this work we utilise a gas cluster ion source for the controlled depth profiling of organic materials that would historically have been too fragile to analyse and obtain quantitative compositional data through the whole thickness of the film. In particular we examine the oxygen diffusion and photo-oxidation kinetics of one of the most commonly used electron acceptor materials for many organic optoelectronic applications, namely PC 61 BM, in both neat films and in blends with polystyrene. Exposure to AM1.5G light and air under ambient conditions, results in a higher level of surface oxidation of blended PC 61 BM:polystyrene than is observed for either pure control film. Gas cluster ion source depth profiling further confirms that this oxidation is strongest at the extreme surface, but that over time elevated oxygen levels associated with oxidised organic species are observed to penetrate through the whole blended film. The results presented herein provide further insights on the environmental stability of fullerene based organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

This study provides new evidence on a long postulated mechanism of phase separation in a polymer/fullerene mixture during spin coating for controlled nanodomains of oriented crystallization and heterojunctions that favor applications in polymer solar cells (PSCs). The simultaneous nanoscale phase separation and crystallization during spin coating of the mixture are traced using in situ grazing-incidence small- and wide-angle X-ray scattering. Combined with the complimentary results from time-resolved optical reflectance spectroscopy, transient stratification of the liquid film during the transition from the flow- to evaporation-dominated stage of spin coating is disclosed; the vertical liquid-liquid phase separation incubates a supersaturated skin layer where fullerene aggregation and polymer crystallization occur and develop concomitantly. Shortly after the transition, the near-surface structural development is largely pinned, leaving the solvent-rich bottom layer to diminish via solvent diffusion and evaporation through the thickened skin layer that finally condenses into the spin-coated film upon solvent depletion. The shear-enhanced surface layering and supersaturation for the surface-down nanostructural development are unexpected in all the existing structural models for PSCs. The mechanistic understanding of coupled vertical phase separation and local nanosegregation provides new insights and alternative strategy to the morphology control of spin-cast PSC active layers in particular and various solution-processed polymeric films in general. [ABSTRACT FROM AUTHOR]

Fullerene C 60 thin films with a thickness of ∼120 nm were synthesized by thermal evaporation method on glass substrate. The deposited thin films are irradiated with 90 MeV Ni ions in the fluence range from 1 × 10 9 to 3 × 10 13 ions/cm 2 . The pristine and irradiated fullerene C 60 thin films are examined to study the effect of energy deposition by 90 MeV Ni ions on the optical and structural properties by UV–visible absorbance spectroscopy and Raman spectroscopy, respectively. UV–visible absorbance spectroscopy study reveals that the absorbance peaks decline with the fluence and at particular fluence (∼3 × 10 13 ions/cm 2 ) all the absorbance peaks disappear. Apart from this, a decrease in band gap has also been observed with increasing fluence. Raman study confirms that the effect of 90 MeV Ni ion irradiation is observed in two phases. In the lower fluence region, polymerization of C 60 molecules is observed and in higher fluence region, destruction of the molecules comes into picture. At fluence 3 × 10 13 ions/cm 2 , fullerene C 60 thin film transformed into amorphous carbon (a-C). The transformation of fullerene into a-C is also confirmed through conductivity measurement. [ABSTRACT FROM AUTHOR]

We have employed a two-photon photoelectron emission microscopy (2P-PEEM) to observe the photocarrier electron dynamics in an organic thin film of fullerene (C60) formed on a highly oriented pyrolytic graphite with a spatial resolution of ca. 135 nm. In this approach, photocarrier electrons in C60 single-layer islands generated by the first pump photon are detected by the second probe photon. These spectromicroscopic observations conducted over a 100×100 nm2 region of C60 islands consistently reproduced the macroscopic two-photon photoemission spectrum of fully covered C60 monolayer film, where the energy of photocarrier electron in the islands was +0.9 eV relative to the Fermi level. Time-resolved 2P-PEEM revealed that the photocarrier electron decayed from the monolayered C60 islands into the substrate with a time constant of 470±30 fs. [ABSTRACT FROM AUTHOR]

Trap-limited bimolecular recombination in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) blend films has been investigated by using photo-induced charge extraction by linearly increasing voltage (photo-CELIV) method. The bimolecular recombination rate is strongly dependent on the photoexcitation density, the PC 61 BM composition and the thermal annealing process, but it slightly depends on the thickness of the blend film. The results show that the trap-limited bimolecular recombination is strongly affected by the distribution of the density of trap state (trap DOS). The higher trap-limited bimolecular recombination rate means the trap DOS centered at lower energy which is beneficial to charge carriers transportation, due to the lower activation energy and faster release rate. On the other hand, the trap-limited bimolecular recombination rate is mainly controlled by the slower species of charge carriers in the blend film when the transport of electrons and holes are strongly unbalanced, and the recombination rate will increase when the transport of electrons and holes becomes more balanced. [ABSTRACT FROM AUTHOR]

The solution processing of pinhole-free methylammonium lead triiodide perovskite-C70 fullerene (MAPbI3:C70) blend films on fluorine-doped tin oxide (FTO)-coated glass substrates is presented. Based on this approach, a simplified and robust protocol for the preparation of efficient electron-transport layer (ETL)-free perovskite solar cells is described. Power conversion efficiency (PCE) of 13.6 % under AM 1.5 G simulated sunlight is demonstrated for these devices. Comparative impedance spectroscopy and photostability analysis of the MAPbI3:C70 and single MAPbI3 films compared with conventional compact TiO2 ETL-based devices are shown. The beneficial impact of using MAPbI3:C70 blend films is emphasized. [ABSTRACT FROM AUTHOR]

The electroabsorption (Stark effect) and photoconductivity of polycrystalline fullerene C in thinfilm samples with radically different geometries (sample 1 with interdigital Cr electrodes and sandwichlike sample 2 with SnO and Al electrodes) have been investigated. It is noteworthy that sample 1 is a submicron grating with 0.88-µm gaps between electrodes. When measuring electroabsorption and photoconductivity, the external voltage does not exceed 4 V. It was assumed that the small gap size may significantly affect the polycrystalline film morphology and surface effects and, as a consequence, the electroabsorption and charge carrier mobility. However, the results of the Stark effect measurements on samples with different geometries differ by only 25%, whereas the spectral photoconductivity values differ by factors of 1-2.5. The increase in photoconductivity may be related to the decrease in the carrier mobility in the sandwich sample or the increase in the number of carriers under the influence of atmospheric oxygen in the surface layer of C sample with interdigital electrodes. [ABSTRACT FROM AUTHOR]

Fullerene C 70 thin films were deposited by resistive heating on glass substrates and the thickness were approximated to be 150 nm. The effect of energy deposition by 55 MeV Si ions on the optical and structural properties of the prepared thin film samples is investigated. The samples were irradiated with 55 MeV Si ions within fluence range from 1 × 10 12 to 3 × 10 13 ions/cm 2 . For optical studies, the pristine and the Si ion irradiated samples are examined by UV–visible absorption spectroscopy and Raman spectroscopy. UV–visible absorption studies reveal that the absorption peaks of irradiated samples decrease with a decrease in the band gap of the thin films. The damage cross-section ( σ ) and radius of damaged cylindrical zone ( r ) are determined as ∼0.6 × 10 −13 cm 2 and ∼1.41 nm, respectively from the Raman spectra. Raman studies also suggest that at higher fluence (up to 3 × 10 13 ions/cm 2 ), the damage caused by the SHI results in partial amorphization of fullerene C 70 thin film. Modification in the surface properties has been investigated by atomic force microscopy; it has revealed that the roughness decreases and average particle size increases with the increase in fluences. [ABSTRACT FROM AUTHOR]

Novel waterborne polyurethane (WPU) was prepared and coated on nylon 12 (Ny12) and fullerene-C60 (Full-C60, 1–10 wt%) composite films using simple dip coating technique. In Ny12/Full-C60 composite, fullerene nanoparticles were dispersed in a wavy layered pattern, whereas coated WPU/Ny12/Full-C60 films depicted uniform pattern of non-overlapping scales. WPU/Ny12/Full-C60 1–10 showed higher values of tensile strength and modulus, 91.4–98.1 MPa and 52.2–57.9 GPa, respectively. In WPU/Ny12/Full-C60 1–10, maximum degradation temperature was increased to 598°C and char yield to 35%. Increasing fullerene content from 1 to 10 wt% decreased maximum peak heat release rate from 209 to 132 kW m−2, i.e., 53% reduction in flammability compared to WPU. [ABSTRACT FROM PUBLISHER]

Trap-induced current multiplication has received tremendous attention in organic photodetectors because it is not required for a pre-amplifier circuit to read weak photocurrent signals. However, a plausible correlation between energy-distin-guishable trap states and device performance has not been established for guiding the device design, a task that remains a significant challenge. Here, we propose an ingenious strategy to demonstrate current multiplication by engineering an ultrathin fullerene (C60) film as hole trap or barrier layer, which illustrates trap-state dynamics through systematical investigations on device current fluctuations in darkness and illumination conditions. The comparison of trap-dependent performances between experimental and control devices clearly shows that the traps play a critical role in generating the multiplication effect. And shallow trap states are estimated to be more favorable for improving the device restorability. Thus, we anticipate that trap engineering, by selectively passivating deep traps whilst retaining shallow ones, will be a fruitful approach for further research, leading to high-performance photodetectors with superior current multiplication and temporal response. (© 2013 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The kinetics and equilibrium of the process of sorption of heavy metals from aqueous electrolyte solutions by polystyrene, fullerene, and polystyrene/fullerene composites have been studied. The kinetics of sorption of copper, nickel, zinc, and cadmium ions by the studied sorbents is described by the pseudo-firstand pseudo-second-order kinetic models. The rate constants of the process of sorption are determined. It is established that the equilibrium isotherm of sorption of copper ions by fullerene is related to the Langmuirtype isotherms. The sorption capacity of a monomolecular layer with reference to the Cu(II) ions is determined as equal to 14.6 mmol/g. Based on the calculated Henry constants, it is shown that the sorption efficiency increases in the series polystyrene < composition < fullerene. [ABSTRACT FROM AUTHOR]

Solid-state semiconductor gas sensors have been attracting a great deal of attention for over two decades, due to their importance in gas analysis and safety applications. Developments are successful concerning sensor properties: all gas sensors produced significant selectivity and sensitivity to the given gases. Size-dependent physical properties are very important in the theory and construction of sensor devices, and metal and semiconductor nanoparticles are basic components of older and even recently used gas-sensitive materials. [Extracted from the article]

The effect of energy deposition in fullerene C 70 (∼150 nm) thin film deposited by resistive heating method on glass, quartz and silicon substrates was investigated. The samples were irradiated with 90 MeV Ni ion beam at the fluences ranging from 1 × 10 12 to 3 × 10 13 ions/cm 2 . The pristine and Ni ion irradiated samples were examined for morphological and optical changes by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), UV–visible absorption spectroscopy and Raman spectroscopy. After ion irradiation, bigger grains are shown on surface as revealed by SEM analysis indicating the agglomeration of the smaller particles into bigger particles at the surface. UV–visible absorption studies reflect that the direct band gap of the film decreases with increase in ion fluence. At higher fluence, fullerene C 70 is transformed into amorphous carbon (a-C) which is confirmed by Raman spectroscopy. The damage cross-section (σ) and radius of the damaged cylindrical zone (r) are approximated to be ∼1.72 × 10 −13 cm 2 and ∼2.3 nm, respectively using Raman active vibrational modes. [ABSTRACT FROM AUTHOR]

Magnetic properties of carbon vary according to its allotropic modifications. Although carbon atom is known as a diamagnetic, some distinctive features point out that its magnetic properties are not that simple. Fullerene C60, a carbon atoms molecule, is proven to have very different magnetizations than other forms of carbon compounds. Rhombohedral fullerene is shown to have ferromagnetic properties, and thus investigations of fullerene as a magnetic material are necessary. Fullerene C60in the form of thin film is also shown to have distinctive magnetic properties. In this paper, remanent magnetization of fullerene thin films, thicknesses of 100 and 250 nm were investigated when films are in the dark and exposed to polarized light. Research showed how light is influencing the material and its magnetization. [ABSTRACT FROM AUTHOR]

Roles of fullerene‐based interlayers in enhancing the performance of organometal perovskite thin‐film solar cells are elucidated. By studying various fullerenes, a clear correlation between the electron mobility of fullerenes and the resulting performance of derived devices is determined. The metallic characteristics of the bilayer perovskite/fullerene field‐effect transistor indicates an effective charge redistribution occurring at the corresponding interface. A conventional perovskite thin‐film solar cell derived from the C60 electron‐transporting layer (ETL) affords a high power conversion efficiency of 15.4%. [ABSTRACT FROM AUTHOR]