Search

BACKGROUND Bio‐sourced (natural) organic materials are often chemically and structurally disordered, such that their structure‐property relationships must be explored using model systems. Eumelanin is an interesting candidate among natural organic materials. RESULTS: In this work, the locations of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of 5,6‐dihydroxyindole (DHI) and 5,6‐dihydroxyindole‐2‐carboxylic acid (DHICA) building blocks (monomers) of the black‐brown biopigment eumelanin, in film form, are studied. The films are fabricated by the spin‐coating technique (i.e., here indicated as DHI‐ and DHICA‐films), which is sometimes followed by ammonia‐induced solid‐state polymerization (i.e., indicated as AISSP‐DHI and AISSP‐DHICA films), as well as by thermal evaporation (i.e., evaporated DHI and DHICA films). From Ultraviolet photoemission spectroscopy (UPS), we deduced the ionization energies (EI) for all DHI‐ and DHICA‐based films to be in the range of 5.34‐5.56 eV and 5.35‐5.80 eV, respectively. The electron affinities (χE) are measurable using inverse photoemission spectroscopy (IPES) for DHI films (3.80 eV) and both evaporated DHI (4.0 eV) and DHICA (3.9 eV) films. On the other hand, the χE values of DHICA, AISSP‐DHI, and AISSP‐DHICA films are estimated with about 0.5 eV of uncertainty. UV‐visible spectroscopy reveals the preferred chromophoric bands for DHICA, AISSP‐DHICA, and DHI are in the range of 300‐330 nm, while AISSP‐DHI exhibits a broadened UV‐visible absorbance. CONCLUSION: Our study paves the way for the design of suitable metal‐eumelanin interfaces for electronic applications. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

We present here a method for the quantitative prediction of the spectroscopic specular reflectivity line-shape in anisotropic layered media. The method is based on a 4 × 4 matrix formalism and on the simulation from the first principles (through density functional theory—DFT) of the anisotropic absorption cross-section. The approach was used to simulate the reflectivity at the oxygen K-edge of a 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) thin film on Au(111). The effect of film thickness, orientation of the molecules, and grazing incidence angle were considered. The simulation results were compared to the experiment, permitting us to derive information on the film geometry, thickness, and morphology, as well as the electronic structure.

10.3390/coatings9050335 11 Fischer D., de la Fuente G.F., Jansen M. A new pulsed laser deposition technique: Scanning multi-component pulsed laser deposition method. In this respect, one should mention (i) scanning multicomponent pulsed laser deposition [[11]], (ii) combined PLD and magnetron sputtering [[12]], (iii) multibeam PLD [[13]], (iv) off-axis PLD [[14]], (v) combinatorial PLD [[15]], and (vi) reactive pulsed laser deposition [[17], [19]]. Various physical vapor deposition (PVD) techniques, such as molecular beam epitaxy, electron beam physical vapor deposition, pulsed laser deposition (PLD), arc discharge, magnetron sputtering and/or ion beam sputtering, are currently used for coating or growing thin films on solid substrates. One should note that the PLD process is based on the capability of laser radiation, usually in the ultraviolet range, to efficiently interact with solid-state or liquid targets, resulting in the congruent ablation of materials from the target surface and subsequent deposition on a substrate. [Extracted from the article]

Due to nonideal behavior, current organic thin film transistor technologies lack the proper models for essential characterization and thus suffer from a poorly estimated parameter extraction critical for circuit design and integration. Organic thin film transistors are often plagued by contact resistance, which is often less problematic in inorganic transistors; consequently, common models used for describing inorganic devices do not properly work with organic thin film transistors. In this work, we fabricate poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} based organic thin film transistors with reduced contact resistance through the introduction of metallic interlayers between the semiconductor and gold contacts. The addition of 10 nm thick manganese interlayer provides optimal organic thin film transistor device performance with the lowest level of contact resistance. Improved organic thin film transistors were characterized using an improved organic virtual-source emission diffusion model, which provides a simple and effective method to extract the critical device parameters. The organic virtual-source emission diffusion model led to nearly perfect prediction using effective gate voltages and a gate dependant contact resistance, providing a significant improvement over common metal–oxide–semiconductor field-effect transistor models such as the Shichman–Hodges model. [ABSTRACT FROM AUTHOR]

In this study, iron phthalocyanine (FePc) thin films were obtained by spin-coating at 80°C and used as the active layer in organic thin-film transistors (OTFTs). The OTFTs have an inverted coplanar structure and were fabricated on plastic substrates made of polyethylene terephthalate. Silicon oxide spin-on glass was used as gate dielectric. The FePc thin films were characterized by UV-Vis spectroscopy, Raman spectroscopy and current–voltage measurements. Interestingly, the electrical characteristics of the FePc OTFTs exhibited a depletion-type behaviour. The threshold voltage extracted was −1.18 V, the subthreshold slope was 0.1 V per decade and the field-effect mobility was 0.002 cm2 Vs−1. As far as we know, this is the first report of FePc-based OTFTs on plastic substrates. [ABSTRACT FROM AUTHOR]

The solution-processed inverted co-planar organic thin film transistor (OTFT) incorporating recessed source-drain-gate and polymer gate dielectric is demonstrated to realize a fully recessed device. The impact of recessed electrodes on the contact resistance ($R_{c}$) and the mobility ($\mu $) is thoroughly investigated by comparing the performance of fully recessed devices, partially recessed (source-drain) devices and standard non-recessed devices. A reduction in $R_{c}$ by two orders of magnitude and 3-fold increase in $\mu $ to attain the values of $60 k\Omega $ - $cm$ (without any surface treatment) and $1.5\times 10^{-2}cm^{2}/Vs$ respectively are achieved in a fully recessed device as compared to the standard non-recessed device. [ABSTRACT FROM AUTHOR]

Nowadays, the use of biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) and cellulose in food packaging applications are replacing the use of different and more conventional oil-derived polymers that are much more expensive and unsuitable for the environment. However, their high transparency to ultraviolet (UV) radiation limits their current commercialization. Therefore, this study focuses on the deposition of organic thin films on commercial PLA and cellulose in order to enhance their performance, in particular for UV shielding. Coatings with different natural and biocompatible (edible) molecules, quinine and p-Coumaric acid, dispersed in different matrices are deposited by comparing different deposition techniques such as spray coating and spin coating. Morphological characterizations are carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM), with spectroscopic characterizations performed by light transmission measurements. Our results show that it is possible to enhance the UV protection of packaging using a suitable deposition with these biocompatible materials. [ABSTRACT FROM AUTHOR]

Organic thin films formed by molecular layer deposition (MLD) are important for next-generation electronics, energy storage, photoresists, protective barriers and other applications. This study uses in situ ellipsometry and quartz crystal microbalance to explore growth initiation and growth rate evolution during MLD of polyurea using aromatic p-phenylene diisocyanate (PDIC) or aliphatic 1,6-hexamethylene diisocyanate (HDIC) combined with ethylenediamine (ED) or 1,6-hexanediamine (HD) co-reactants. During the first 10–20 cycles of growth, we show the growth rate can increase and/or decrease substantially depending on the substrate as well as the flexibility, length, and structure of the isocyanate and amine reactants used. The transition from initial to steady growth is attributed to a change in active surface site density as the growth proceeds, where the number of sites is determined by a balance between steric effects that block active sites, double reactions that consume multiple active sites, and precursor physisorption and sub-surface diffusion that create new active sites, where the extent of each mechanism depends on the precursors and deposition conditions. Results shown here provide useful insight into mechanisms needed to control growth of ultra-thin organic films for advanced applications. [ABSTRACT FROM AUTHOR]

The effect of silver doped ZnO (ZnO:Ag) nano-particles in the hole transport buffer layer of thin film organic solar cell was studied in this article. Polymers molecules blend composed of poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric-acid-methyl-ester (P3HT:PCBM) was used as a medium of solar absorber to investigate the effect of metal nano-particles in the transport layer. Furthermore, an additional improvement on the charge transport processes were expected by co-doping of dimethyl sulfoxide solvent additive on the absorber layer of the solar cells. Optical properties of the solar absorber films of the devices showed significant enhancement of absorbency from the use of metal nano-particles. As a result, device performances have been boosted as determined from improved device parameters such as the fill-factor and short-circuit current density were increased by 16% and 58%, respectively. The power conversion efficiency has increased from 2.56% (pristine devices) to a maximum of 4.88% for devices doped with 5 wt% dimethyl sulfoxide and 1.5 mg ZnO:Ag nano-particles. [ABSTRACT FROM AUTHOR]

Electroactive coatings based on non-conjugated redox-active polymers have increased in popularity with the development of thin film organic batteries. Control over coating deposition, redox-activity, and ion transport are key to improving their energy storage performance. In this work, the synthesis, solution state electrochemical characterization, and layer-by-layer (LbL) assembly of a nitroxide-based polycation and polyanion are presented. Solution state electrochemical characterization indicates that the rate of electron transfer for the nitroxide polyanion is much higher as compared to the nitroxide polycation. LbL thin films of the nitroxide polyanion and nitroxide polycation are assembled, demonstrating linear growth and tunable thickness (28 nm/layer pair). This work confirms that the ion transport mechanism of the LbL films during the redox reaction is influenced depending on the charge of the terminating layer, where the nitroxide polyanion can participate in self-doping, which leads to a contribution from cation transport. The nitroxide polyanion-terminated film also exhibits a higher capacity and a slightly reduced charge transfer resistance. However, it was also observed that a more pronounced capacity fade occurred for the polyanion-terminated film than the polycationterminated film. Taken together, this highlights how oppositely charged radical-containing polyelectrolytes can form electroactive coatings for possible applications in energy storage or sensing. [ABSTRACT FROM AUTHOR]

Arrays of flexible organic thin-film transistors (OTFTs) are the prerequisite to realize commercialization of flexible electronics. However, photolithography and print techniques are uneasy to combine high performance, high integration density, and compatibility with flexible substrates to fabricate OTFT arrays. In this work, OTFT arrays with high resolution, flexibility and process convenience are patterned by femtosecond laser (fs-laser). 1 cm2 of area can accommodate up to 6250 transistors with sharp edges and short channel lengths by selective processing. Furthermore, micron-scale resolution flexible image sensor with integration potential were verified. Hence, these results will impel the development of flexible wearable electronic devices in the future. [ABSTRACT FROM AUTHOR]

This work reports the use of the slot‐die (SD) coating solution processing method to fabricate large‐area organic thin films composed of photochromic dyes as UV indicators and UV light absorbers as UV filters on polyethylene terephthalate flexible substrates. This is the first demonstration of large‐area SD coated organic photochromic films and UV filters. Impressively, highly uniform photochromic films comprised of small molecules are formed in air, from green solvents (i.e., alcohols) and show rapid color changes upon external stimuli (i.e., light and heat). The UV filters processed under the same conditions and comprised of only small molecules show highly transparent films in the visible and near‐IR range with T% > 97%@550 nm and excellent UV blocking ability. The work highlights the utility of roll‐to‐roll compatible SD‐coating methods to make prototype organic devices in an academic laboratory setting and opens the door for additive manufacturing of simple and low‐cost UV active films for healthcare and electronic applications. [ABSTRACT FROM AUTHOR]

Molecular packing patterns are crucial factors determining electron/energy transfer processes that are critical for the optoelectronic properties of organic thin film devices. Herein, the polarization-selective ultraviolet/infrared (UV/IR) mixed frequency ultrafast spectroscopy is applied to investigate the relative molecular orientations in two organic thin films of 7-(diethylamino)coumarin-3-carboxylic acid (DEAC) and perylene. The signal anisotropy changes caused by intermolecular energy/electron transfers are utilized to calculate the cross angles between the electronic transition dipole moment of the donor and the vibrational transition dipole moments of the acceptor, yielding the relative orientation between two adjacent molecules. Using this method, the relative orientation angle in DEAC film is determined to be 53.4°, close to 60° of its single crystalline structure, and that of the perylene film is determined to be 6.2°, also close to −0.2° of its single crystalline structure. Besides experimental uncertainties, the small difference between the angles determined by this method and those of single crystals also results from the fact that the thin film samples are polycrystalline where some of the molecules are amorphous. [ABSTRACT FROM AUTHOR]

While great progress has been achieved in the research of various solution-processed organic semiconductors, the randomized crystal orientations and charge carrier mobility variations have posed tremendous challenges to implement the organic semiconductors for organic electronic device applications. Among the miscellaneous polymer additives reported to tune the crystal growth and modulate charge transport, poly(α-methyl styrene) (PαMS) has been extensively studied for its capability to improve semiconductor crystallization, reduce bulk crystal misorientation, induce phase segregation, enhance morphological uniformity and boost electrical performance of organic thin film transistors and organic electronic devices. In the first section of this article, we review the recent progress of organic electronics and highlight the crystal misorientation and mobility variation as the challenges that need to be overcome. Then, the various merits from mixing polymeric additives with organic semiconductors are discussed. In the second section, we provide an overview of the previous works that employ PαMS for regulating the crystal orientation alignment and modulating charge transport of miscellaneous solution-processed small-molecular organic semiconductors including 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) and 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TESADT). By discussing these important examples, we intend to demonstrate that PαMS can be versatilely implemented to improve other new organic semiconductor crystallization and mobility for high-performance organic electronic applications. [ABSTRACT FROM AUTHOR]

Thin‐film organic materials are broadly used to study amorphous stabilization of active pharmaceuticals, control explosive detonation phenomena, and introduce insulation in novel thermal barriers. Their synthesis, however, introduces defects and thickness variations that warrant careful characterization of local thermophysical properties such as thermal conductivity and mass density. Here, wide bandwidth (200 Hz to 20 MHz) frequency–domain thermoreflectance (FDTR) is demonstrated to simultaneously extract the thermal conductivity and mass density of 1 μm physical vapor‐deposited indomethacin films on Si and SiO2 substrates, as well as 10 and 100 μm films on Si. By assuming a bulk specific heat capacity, mass densities are determined with FDTR measurements of volumetric heat capacity and are in good agreement with the literature, as well as models based upon a dependence on porosity and the kinetic theory for phonons. Lastly, it is found that for broad‐band FDTR measurements, insulating substrates provide improved fidelity for the extraction of thermal conductivity and volumetric heat capacity in organic thin films. Overall, this work demonstrates the potential for FDTR as a non‐contact method to determine microscale mass density variations across the surface and thickness of organic thin films. [ABSTRACT FROM AUTHOR]

Corrosion monitoring and management has been at the center of structural health monitoring protocols due to its damaging effects on metallic structures. Current corrosion prevention and management programs often fail to include environmental factors such as Cl− ions and surface wetness. Early detection of these environmental factors can prevent the onset of corrosion and reduce repair and maintenance-related expenses. There is growing interest in creating solution-processed thin film environmental sensors with high sensitivity to corrosion precursors, low-cost fabrication, and small footprint, rendering them viable candidates for investigation as potential corrosion sensors that could be easily integrated into existing structures and screen printed or patterned directly into surface coatings. In this work, we have implemented C60-based n-type organic thin film transistors (OTFTs) with functionalized graphene oxide for humidity sensing and functionalized graphene nanoparticles for Cl− ion detection, using low-cost solution processing techniques. The reduced graphene oxide (rGO)-coated OTFT humidity sensor is designed for the qualitative estimation of surface moisture levels and high levels of humidity, and it exhibits a relative responsivity for dry to surface wetness transition of 122.6% to surface wetness, within a response time of 20 ms. We furthermore implemented an in-house synthesized hydrogenated graphene coating in conjunction with a second OTFT architecture for Cl− ions sensing which yielded a sensitivity of 4%/ppm to ultrafine ionic concentrations, over an order of magnitude lower than the range identified to cause corrosion in aircraft structures. [ABSTRACT FROM AUTHOR]

The article presents the discussion on efficient method for asymmetric synthesis of acyclic α-tertiary amine derivatives. Topics include direct enantioselective aminations of α-branched ynones under chiral phosphoric acid catalysis; and thermogravimetric analysis indicating the chiral polyesters exhibiting good thermal stability.

Comprehensive Summary: Fabricating n‐type organic thin film transistors (OTFTs) based on small molecules via solution processing under atmospheric conditions remains challenging. Blending small molecules with polymer is an effective strategy to improve the solution processibility and air stability of the resulted devices. In this study, polystyrene was chosen to blend with n‐type small molecule DPP1012‐4F to enhance the continuity of the semiconductor layer and maintain a favorable edge‐on stacking of semiconductors. The introduction of high‐boiling point 1‐chloronaphthalene as a solvent additive in the blending system can reduce the grain boundary defects in the microscopic morphology. These changes in aggregation behavior are confirmed by X‐ray diffraction, atomic force microscopy and polarized optical microscopy analyses. Via bar‐coating of the semiconductor layers in air, the electron mobility of the resulted OTFTs under the optimal condition is 0.73 cm2·V–1·s–1, which is amongst the highest n‐type small molecule‐based OTFTs with active layers prepared in air up to now. These results show a great potential of the blending strategy in industrial roll‐to‐roll manufacture of high‐mobility n‐type OTFTs. [ABSTRACT FROM AUTHOR]

A Cd-doped ZnO nano-composite (Cd:ZnO) was synthesized using wet chemistry, and then incorporated into the photo-active layer of a thin film organic solar cell (TFOSC) to assist photon harvesting. The nano-composite (NC) formed different sized nano-structures that are beneficial to optical absorption and charge transport processes in the TFOSC. The effects on the NC were studied using a solar absorber medium composed of a poly(3-hexylthiophene) (P3HT) and 6-6-phenyl-C61-butyric acid methyl ester (PCBM) blend with standard device architecture: ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al. The electrical and optical properties of the photoactive films were investigated at various doping levels of Cd:ZnO NC in the medium. The composite showed interesting local surface plasmon resonance, which significantly impacted on the performance of the cells. Consequently, the power conversion efficiency of the TFOSC grew by 84% compared to the reference cell. It is also noted that Cd:ZnO is environmentally stable and compatible for solution device processing. [ABSTRACT FROM AUTHOR]

(a) Absorption & PL spectra of NiPc thin film, (b) The variation of MC with the magnetic field at different bias voltages, (c) Schematic structure of organic solar cells, and (d) J-V curve of organic solar cells with NiPc layer. [Display omitted] • Magneto-conductance (MC) and opto-electrical properties of NiPc layer have been explored. • Transport properties & the MC study have been discussed with trap assisted bipolaron mechanism. • The thermally activated mobility is calculated in SCLC region from the J-V characteristics. • The NiPc thin film has been successfully introduced in organic solar cells. • The PCE of organic solar cell using 15 nm NiPc buffer layer is 3.17%. The nickel phthalocyanine (NiPc) thin film has been explored for magneto-conductance and optoelectrical properties. The surface morphology and the opto-electrical properties of thin films of NiPc have been observed as a good candidate for the applications in polymer solar cells. The AFM images show an almost continuous surface over the studied area. The spin interaction, the disordering of the spins part, and their suitable models have been discussed by the magneto-conductance properties of the thin films. The relaxation time of carriers and traps filling phenomena with applied bias are discussed by the impedance spectroscopy. The thin films of NiPc have been introduced as a hole interface buffer layer in the standard structure of P3HT: PCBM solar cells. The power conversion efficiency (PCE) of the optimized solar cell with NiPc is ∼3.17% and the fill factor (FF) is ∼69%., these device parameters are higher (PCE increased by ∼65% and FF by ∼39%) as compared to the organic solar cells fabricated without NiPc thin films in the same batch. The improved performance of organic solar cells attributed due to lowering the series and shunt resistance. [ABSTRACT FROM AUTHOR]

This research explores performance attributes of bottom gate top contact (BGTC) and bottom gate bottom contact (BGBC) organic thin film transistors (OTFT). To upgrade the performance characteristics, a region of 5nm with high concentration of carrier is tallied neighboring contacts. The drain current for BGTC is –18.6μA as compared to –5.1μA of BGBC transistor. Also, it is established that the innate attributes of BGTC are better than those of their counterparts, which is typically considered because of the inadequate contact attributes and mediocre semiconductor quality of BGBC OTFT. The analysis showed that upon varying the length of the channel ranging from 5μm to 40μm, there was a significant change in the drain current of BGTC and BGBC devices. For the same values of VGS and VDS (0V to –5V) where drain current in BGTC structure varied from –129.86μA to –13.69μA, whereas for their counterparts it ranged from –37.10μA to –3.76μA for channel length equal to 5μm and 40μm respectively. Also, with the varying doping strength ranging from 1012 cm–3 to 1016 cm–3 for BGBC device, drain current varied from –2.15μA to –18.52μA for BGTC whereas for BGBC it varied from –0.19μA to –7.09μA keeping VGS and VDS –5 V, yielding that upon varying the doping strength, where for BGTC ID changed by a factor of 8.6, the BGBC device showed a considerable change by a factor of 37.3. Likewise, mobility, threshold voltage, sub-threshold swing and transconductance also showing better performance with the P + insertion. These variations in the innate attributes are primarily due to the deficiency of carriers at the interface of source and channel, leading to a greater drop in the potential, which is more prominent for the bottom gate bottom contact devices. [ABSTRACT FROM AUTHOR]

In this letter, organic thin-film transistors (OTFTs) with various interface modification conditions are fabricated and characterized. In addition to chemically homogeneous dielectric surfaces to enhance electrical characteristics of devices, morphologically homogeneous surfaces are also needed to achieve good device-to-device uniformity of OTFTs. The different charge trap densities at the dielectric interface and in pentacene film is responsible. [ABSTRACT FROM AUTHOR]

Hybrid MoS2-based molybdenum thiolate thin films with selected organic motifs are grown using molecular layer deposition (MLD), allowing for tunable optoelectronic film properties. The thin films are deposited at 170 °C using the metal precursor molybdenum hexacarbonyl and one of the three organic precursors: 1,2-ethanedithiol, 1,4-butanedithiol, and 1,4-benzenedithiol. The resulting Mo-ethanethiolate, Mo-butanethiolate, and Mo-benzenethiolate films show saturating growth with a growth per cycle of 1.2, 1.0, and 1.5 Å/cycle, respectively. Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray absorption spectroscopy, and x-ray diffraction are used to characterize the as-deposited films. Results show that by changing the organic precursor, the film composition as well as the optical and electronic properties can be tuned. The Mo-thiolate films grown with benzenedithiol exhibit the lowest resistivity, which at 12 mΩ cm is ∼400 times more conductive than Mo-thiolates grown with aliphatic organic linkers. All three backbone chemistries of the Mo-thiolates show an optical bandgap between 2.3 and 2.4 eV and mild photoconductivity response. The MLD of these Mo-thiolate films demonstrates the synthesis of transition metal-organosulfur thin films with tunable properties. [ABSTRACT FROM AUTHOR]

Abstract.Inverted Bulk heterojunctions (Ag/MoO3/PCDTBT-PC70BM/ZnO/ITO) Organic Solar cells, based on Organic (Polymer) materials is fabricated and characterized in this work. PCDTBT-PC70BM was synthesized by chloroform, chlorobenzene and odichlorobenzene (organic solvent). Surface morphology of ZnO and PCDTBT-PC70BM were studied. Bulk heterojunctions of active material are formed by the mixture of PCDTBT donor and PC70BM an acceptor in a random manner. For Sufficient transportation of charge carrier (electron and hole), hole transport (HT) and electron transport (ET) layers was deposited. ZnO is used as an ETM and synthesized by using Sol-Gel technique. MoO3 thin film deposited over the active material, enhances hole transformation because of band gap tuning with Ag and active materials. Absorbance and Photoluminescence spectra of polymer material with different organic solvents were studied and results were discussed in this work. o-dichlorobenzene enhance the absorption of PCDTBT/PC70BM. At 400 nm, 90% of sun light is absorbed, and 70% absorption is figure out in 500- 550nm wavelength. The Photo-luminescence of PCDTBT/PC70BM thin film in different organic solvents is ranging from 650nm to 750nm. At 700nm, 20% is shown for chloroform, 40% for chlorobenzene and highest 80% is achieved by o-dichlorobenzene. J-V value is obtained from a solar simulator which irradiates the sun spectrum 1.5 AM, for all the devices having cell area 0.045 cm². For concentration (1:1) ratio in different organic solvents like chloroform, chlorobenzene and o-dichlorobenzene, (3.5, 4.2, and 5.8) %, PCE were obtained respectively. [ABSTRACT FROM AUTHOR]

We have investigated the growth and stability of molecular ultra-thin films, consisting of rod-like semiconducting para-hexaphenyl (6P) molecules vapor deposited on ion beam modified TiO2(110) surfaces. The ion bombarded TiO2(110) surfaces served as growth templates exhibiting nm-scale anisotropic ripple patterns with controllable parameters, like ripple depth and length. In turn, by varying the ripple depth one can tailor the average local slope angle and the local step density/terrace width of the stepped surface. Here, we distinguish three types of substrates: shallow, medium, and deep rippled surfaces. On these substrates, 6P sub-monolayer deposition was carried out in ultra-high vacuum by organic molecular beam evaporation (OMBE) at room temperature leading to the formation of islands consisting of upright standing 6P molecules, which could be imaged by scanning electron microscopy and atomic force microscopy (AFM). It has been found that the local slope and terrace width of the TiO2 template strongly influences the stability of OMBE deposited 6P islands formed on the differently rippled substrates. This effect is demonstrated by means of tapping mode AFM, where an oscillating tip was used as a probe for testing the stability of the organic structures. We conclude that by increasing the local slope of the TiO2(110) surface the bonding strength between the nearest neighbor standing molecules is weakened due to the presence of vertical displacement in the molecular layer in correspondence to the TiO2 atomic step height. [ABSTRACT FROM AUTHOR]

Organic thin film transistors (OTFTs) have been explored because of their advantageous features such as light-weight, flexible, and large-area. For more practical application of organic electronic devices, it is very important to realize OTFTs that are composed only of organic materials. In this paper, we have fabricated p+-i-p+ type of OTFTs in which an intrinsic (i) regioregular poly (3-hexylthiophene) (P3HT) layer is used as the active layer and highly doped p-type (p+) P3HT is used as the source and drain electrodes. The 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) was used as the p-type dopant. A fabricating method of p+-i-p+ OTFTs has been developed by using SiO2 and aluminum films as capping layers for micro-scaled patterning of the p+-P3HT electrodes. The characteristics of the OTFTs were examined using the photoelectron spectroscopy and electrical measurements. We demonstrated that the fabricated p+-i-p+ OTFTs work with carrier injection through a built-in potential at p+/i interfaces. We found that the p+-i-p+ OTFTs exhibit better FET characteristics than the conventional P3HT-OTFT with metal (Au) electrodes, indicating that the influence of a carrier injection barrier at the interface between the electrode and the active layer was suppressed by replacing the metal electrodes with p+-P3HT layers. [ABSTRACT FROM AUTHOR]

The organic film co-deposited by Zinc Phthalocyanine (ZnPc) and Lead Phthalocyanine (PbPc) was used as the active layer of the vertical organic film diode, and we obtained the co-deposition ratio of the devices with the better performance of 1:1. We made the vertical organic thin film transistor (VOTFT) with the same process again, compared the co-deposited VOTFT with the VOTFT with a single organic material (ZnPc, PbPc) as the active layer and tested the static operating characteristics of the device. The results show that the carrier mobility of ZnPc-PbPc-VOTFT is more than three times higher than that of ZnPc-VOTF and PbPc-VOTFT. When V DS = 3 V and V GS = 0. 2 V, the output current I DS of ZnPc-PbPc-VOTFT is up to 0.2 mA, which is 12 times that of ZnPc-VOTFT and 27 times that of PbPc-VOTFT. Overall, the electrical performance of ZnPc-PbPc-VOTFT is better than ZnPc-VOTFT and PbPc-VOTFT. A vertical organic thin film transistor has been prepared using zinc phthalocyanine (ZnPc) and lead phthalocyanine (PbPc) co-deposited materials as active layers. After testing, the contact barrier of the ZnPc-PbPc organic thin film device was effectively reduced compared to organic thin film devices with single component materials (ZnPc and PbPc). Carrier concentration and mobility of the ZnPc-PbPc organic thin film transistor were greatly improved. [ABSTRACT FROM AUTHOR]

Uniform deposition across large areas of an organic layer is one of the challenges for the industrial application of solution-based organic light‐emitting diode (OLED). In this paper, we propose an organic thin film deposition method for OLED using a micro multi-nozzle jet coating process. The developed micro multi-nozzle jet head consists of eighteen nozzles (100 μm diameter), a side suction line, inlets, and a nozzle protection outer hole. To demonstrate organic thin film deposition for OLED lighting device fabrication, a poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) solution was used as a hole injection layer (HIL). Thickness uniformity of the PEDOT:PSS thin film was analyzed by regulating the jetting pressure. Through single-path coating of twelve successive stable column-jet flows, PEDOT:PSS organic film of 26 mm width was coated on an ITO substrate at 1 m/s head speed. The PEDOT:PSS thin film of 24.25 ± 1.55 nm (CV = 6.39%) thickness was obtained by the proposed coating method. For the feasibility test, OLED lighting devices with emission areas of 20 mm × 20 mm and 70 mm × 70 mm were successfully fabricated using PEDOT:PSS films deposited by a micro multi-nozzle jet coating method. [ABSTRACT FROM AUTHOR]

[Display omitted] Porous polymeric covalent organic frameworks (COFs) have been under intense synthetic investigation with over 100 unique structural motifs known. In order to realize the true potential of these materials, converting the powders into thin films with strict control of thickness and morphology is necessary and accomplished through techniques including interfacial synthesis, chemical exfoliation and mechanical delamination. Recent progress in the construction and tailored properties of thin film COFs are highlighted in this review, addressing mechanical properties as well as application-focused properties in filtration, electronics, sensors, electrochemistry, magnetics, optoelectronics and beyond. Additionally, heterogeneous integration of these thin films with other inorganic and organic materials is discussed, revealing exciting opportunities to integrate COF thin films with other state of the art material and device systems. [ABSTRACT FROM AUTHOR]

The presence of lateral leakage through organic semi-conductive layers in organic light-emitting diodes (OLEDs) array prevents excellent performance of display application especially in high resolution one. To mitigate the impact of lateral leakage and figure out the detailed mechanism, an accurate model involving simultaneous measurements of OLED and organic thin film transistor (OTFT) is proposed. The results establish that the lateral leakage generates to the adjacent off-state devices due to a p-type thin film transistor-like effects with the cathode playing a gate function. The proposed technique reveals that higher gate voltage and source voltage brings in more serious lateral leakage, corresponding to the electric field effect. It also shows a temperature dependence when the environment has changed. The research opens the possibility of considering the influences of semi-conductive layers and parallel structural devices on more self-luminous arrays for their actual application. [ABSTRACT FROM AUTHOR]

Epsilon‐near‐zero (ENZ) optical material has been employed in a number of novel linear and nonlinear optical applications, owing to the vanishing polarization upon an incident optical wave. In a uniaxial medium possessing hyperbolic energy–momentum dispersion of optical wave, ENZ can take place at ordinary and extraordinary permittivities. Organic thin films presenting a lamellar structure have been reported to exhibit a transverse negative hyperbolic dispersion with ENZ at ordinary permittivity. Here, organic thin film with ENZ at extraordinary permittivity is demonstrated. Newly synthesized polymethine dye (i.e., squaraine indolenine triethyleneglycol molecule) self‐organizes to form a layered structure in a pristine film, and both transverse negative and positive hyperbolic dispersions are observed at visible wavelengths. Analysis of tens‐nanometer‐thick pristine film shows that both ENZ and epsilon‐near‐pole (ENP) occur at longitudinal as well as transverse component of dielectric permittivity. Optical characterization of squaraine pristine film is presented, and the importance of transverse positive hyperbolic dispersion in such monolithic thin film is discussed. [ABSTRACT FROM AUTHOR]

The photo(electro)chemical reduction of water and oxygen to produce hydrogen (water‐splitting) and hydrogen peroxide, respectively, are well developed with inorganic semiconductors. In contrast, organic π‐conjugated polymers, especially precisely synthesized ones, have been extensively studied as photoharvesting and charge‐separating materials in dry photoelectron‐conversion devices, such as organic photovoltaic cells. However, the use of conjugated polymers as photocathodes; i.e., photoelectrocalatalytic reduction‐active materials in direct contact with aqueous electrolytes, has been less explored. This review describes the fundamentals of the electrochemistry of water and oxygen reduction, as well as organic semiconductor functions for photocathode activity in water, along with figures of merit for organic photocathodes used to practically produce hydrogen and hydrogen peroxide. Recent research on conjugated polymers in this field is then surveyed after briefly referring to early trial‐and‐error investigations using conventional conjugated polymers. Basic and very simple designs of robust polythiophene films are demonstrated as examples of successful materials which act as both visible‐light harvesters and catalysts for hydrogen evolution and the production of hydrogen peroxide, and as counterparts in combination with conventional oxygen‐evolution catalysts. Perspectives for this emerging field are also briefly provided. [ABSTRACT FROM AUTHOR]

Strong-coupling between excitons and confined photonic modes can lead to the formation of new quasi-particles termed exciton-polaritons which can display a range of interesting properties such as super-fluidity, ultrafast transport and Bose-Einstein condensation. Strong-coupling typically occurs when an excitonic material is confided in a dielectric or plasmonic microcavity. Here, we show polaritons can form at room temperature in a range of chemically diverse, organic semiconductor thin films, despite the absence of an external cavity. We find evidence of strong light-matter coupling via angle-dependent peak splittings in the reflectivity spectra of the materials and emission from collective polariton states. We additionally show exciton-polaritons are the primary photoexcitation in these organic materials by directly imaging their ultrafast (5 × 106 m s−1), ultralong (~270 nm) transport. These results open-up new fundamental physics and could enable a new generation of organic optoelectronic and light harvesting devices based on cavity-free exciton-polaritons Exciton-polaritons are typically formed in organic systems when the molecules are confined between metallic or dielectric mirrors. Here, the authors reveal that interactions between excitons and moderately confined photonic states within the bare organic film can also lead to polariton formation, making them the primary photoexcitation. [ABSTRACT FROM AUTHOR]

The active region of organic thin film transistors (OTFTs) is usually sensitive to moisture and O2 in the air ambient, which hinders their practical applications. In this study, the effects of air ambient on characteristics of unpassivated 2,8-difluoro-5,11-bis (triethylsilylethynyl) anthradithiophene (dif-TES-ADT) OTFTs are clarified. The device is much more sensitive to H2O vapor than O2, although both of which cause TFT instability. To improve the environmental stability, inkjet-printed passivation of the fluoropolymer CYTOP and UV curing adhesive are compared. It is found that the CYTOP passivation is well compatible with the organic channel while the UV curing adhesive has excellent barrier ability to both H2O vapor and O2. Then CYTOP/UV adhesive bilayer passivation combining advantages of both materials is introduced to achieve stable operation of OTFTs, which can resist saturated H2O vapor and O2 for 25 days. [ABSTRACT FROM AUTHOR]

We report on the development of a Quartz Crystal Microbalance-based sensor targeting the monitoring of the pertechnetate ion (TcO4-) in groundwater exploiting the anion-specific adsorptive behaviour of a novel Ag-4,4-bipyridine metal-organic framework (MOF) thin film. This MOF was first reported by Zhu et al. [Environ. Sci. Technol. Lett., 4, 316, (2017)] to selectively and irreversibly adsorb ReO4-, a non-radioactive chemical surrogate for TcO4-, in the form of bulk crystals. The structure of our film was characterised by XRD and SEM and its response and selectivity were evaluated by monitoring the changes in the resonant frequency of the QCM as a function of the concentration of ReO4- and other interferents. Finally, the interaction of all the analytes with the film was modelled with adsorption isotherms including Langmuir, Freundlich and Sips. We show that the behaviour of the thin film is substantially different from that of the bulk crystals. [ABSTRACT FROM AUTHOR]

Organic thin film transistor (OTFT) based nonvolatile memory has made significant progress due to its biocompatibility, flexibility, and low cost, in which ferroelectric transistor memory and floating gate transistor memory play the main roles in organic nonvolatile transistor memory. Here, a novel layered hybrid structure OTFT nonvolatile memory is invented by combining ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene) P(VDF‐TrFE) with a floating gate layer utilizing CdSe/ZnS quantum dots (QDs), which integrates the advantages of ferroelectric memory and floating gate memory. The core–shell structured CdSe/Zns QDs are acted as robust charge trapping centers due to their band structure similar to a quantum well, preventing the back diffuse of trapped charges, while P(VDF‐TrFE) provides additional polarized electric field to modulate the capture of charge. The resultant devices exhibit high on‐state current (≈10−5 A), low off‐state current (≈10−10 A), excellent switch ratio (≈105), and retention characteristic (>104 s). Furthermore, a superior memory window, more than 85.6% of scanning voltage range, higher than most reported organic transistor memories, is achieved, which endows the device wide operating condition and significant discrimination between on and off state. The fine‐structured OTFT memory opens up a unique path for desirable memory to meet the growing demand of microelectronic industry. [ABSTRACT FROM AUTHOR]

The bulk morphology of the active layer of organic solar cells (OSCs) is known to be crucial to the device performance. The thin film device structure breaks the symmetry into the in-plane direction and out-of-plane direction with respect to the substrate, leading to an intrinsic anisotropy in the bulk morphology. However, the characterization of out-of-plane nanomorphology within the active layer remains a grand challenge. Here, we utilized an X-ray scattering technique, Grazing-incident Transmission Small-angle X-ray Scattering (GTSAXS), to uncover this new morphology dimension. This technique was implemented on the model systems based on fullerene derivative (P3HT:PC71BM) and non-fullerene systems (PBDBT:ITIC, PM6:Y6), which demonstrated the successful extraction of the quantitative out-of-plane acceptor domain size of OSC systems. The detected in-plane and out-of-plane domain sizes show strong correlations with the device performance, particularly in terms of exciton dissociation and charge transfer. With the help of GTSAXS, one could obtain a more fundamental perception about the three-dimensional nanomorphology and new angles for morphology control strategies towards highly efficient photovoltaic devices. Morphology of organic thin film, including the in-plane and out-of-plane directions, plays a crucial role in determining the performance of organic solar cells, yet the characterisation is challenging for the out-of-plane direction. Here, the authors use GTSAXS to uncover the nanomorphology in this dimension, and show how it affects exciton dissociation and charge transfer. [ABSTRACT FROM AUTHOR]

This is the first study of the catalytic graphitization of Black Spruce (Picea mariana) which has successfully discovered the formation of single crystal graphitic carbon structures with a very high conductivity over 850 S/m implemented in the cathode of a coin cell battery. Renewable carbon with this conductivity is suitable for use in bio-electronics, organic thin film transistors, fuel cells, organic batteries, supercapacitors and sensing device applications. The P. mariana was doped with iron nitrate nanoparticle precursor, and sequentially thermo-catalyzed in presence of helium at temperatures between 300 and 800 °C. Transmission electron micrographs reveal formation of graphitic structures with an interplanar distance of ∼0.33 nm resembling single crystal graphite structure. Raman spectroscopy and X-ray diffraction studies confirm the presence of nano-layered carbon, and the high conductivity was observed in Fe-free residual graphite. Thus, using iron nitrate as a catalyst promotes the formation of single crystal graphitic structures at a significantly reduced thermal energy than traditional pyrolysis treatment and opens a new frontier for sustainable bio-electronics and energy materials manufacturing. [Display omitted] • Renewable carbon from woody biomass yields materials for use in energy applications. • Demonstrated applications of a cathode in coin cell battery and a conductor. • Iron nitrate catalyst promotes formation of graphite structure at lower temperatures. • Single crystal graphitic structures with an exceptional conductivity over 850 S/m. • Raman and XRD studies confirm the presence of nano-layered carbon. [ABSTRACT FROM AUTHOR]

Tailored nanostructures provide at-will control over the properties of light, with applications in imaging and spectroscopy. Active photonics can further open new avenues in remote monitoring, virtual or augmented reality and time-resolved sensing. Nanomaterials with χ(2) nonlinearities achieve highest switching speeds. Current demonstrations typically require a trade-off: they either rely on traditional χ(2) materials, which have low non-linearities, or on application-specific quantum well heterostructures that exhibit a high χ(2) in a narrow band. Here, we show that a thin film of organic electro-optic molecules JRD1 in polymethylmethacrylate combines desired merits for active free-space optics: broadband record-high nonlinearity (10-100 times higher than traditional materials at wavelengths 1100-1600 nm), a custom-tailored nonlinear tensor at the nanoscale, and engineered optical and electronic responses. We demonstrate a tuning of optical resonances by Δλ = 11 nm at DC voltages and a modulation of the transmitted intensity up to 40%, at speeds up to 50 MHz. We realize 2 × 2 single- and 1 × 5 multi-color spatial light modulators. We demonstrate their potential for imaging and remote sensing. The compatibility with compact laser diodes, the achieved millimeter size and the low power consumption are further key features for laser ranging or reconfigurable optics. Spatial light modulators (SLM) provide tailored light fields for many applications. Here, the authors present an SLM device based on an organic electro-optic material that manipulates the properties of individual pixels by electronic signals at speeds up to 50 MHz. [ABSTRACT FROM AUTHOR]

Characterization of thin films is of paramount importance for evaluating material processing outcomes/efficiency as well as establishing structure–property/performance relationships. This article introduces grazing‐incidence diffraction tomography (GID tomography), a technique that combines grazing‐incidence X‐ray scattering and computed tomography to quantitatively determine the dimension and orientation of crystalline domains in thin films without restrictions on the beam coherence, substrate type or film thickness. This computational method extends the capability of synchrotron beamlines by utilizing standard X‐ray scattering experiment setups. [ABSTRACT FROM AUTHOR]

Conventionally, silver (Ag) electrodes for organic thin-film transistors (OTFTs) are prepared by evaporated method at high temperature. In this work, we report a new methodology to fabricate the Ag source/drain electrodes of flexible OTFTs arrays by chemically plated technique on polyimide substrate at room temperature. The indacenodithiophene-co-benzothiadiazole (IDT-BT) OTFTs with chemically plated electrodes obtain the saturation mobility of 0.25 cm $^{2}\text{V}^{-1}\text{s}^{-1}$. Furthermore, compared with high-temperature thermal evaporation method, the subthreshold swing of the IDT-BT OTFTs decreases from 1.97 to 0.89 V/dec with chemically plated Ag source/drain electrodes. The smaller threshold voltage and contact resistance are also obtained, owing to the change of work function. The bending tests indicate that the electrical properties of the devices maintain unchanged during tensile bending at a radius up to 1.4 mm. Moreover, the electrical property of the devices remains stable at a tensile bending cycle of 1000 cycles at a radius of 2.5 mm. This proposed methodology has great potential for flexible and wearable electronic devices. [ABSTRACT FROM AUTHOR]

The hole mobility of an organic semiconductor film that consists of N,N'‐di (1‐naphthyl)‐N,N'‐diphenyl‐benzidine (α‐NPD) is evaluated at various film formation processes, such as vacuum deposition and capillary injection. The mobility varies with the film formation process. From the temperature dependence of mobility, the Poole−Frenkel model and disorder model are discussed. From the analysis based on the Poole−Frenkel model, activation energies of the vacuum‐deposited film, the slowly cooled‐melted film, and the rapidly cooled‐melted film are 0.28, 0.20, and 0.40 eV, respectively. This result suggests that organic semiconductor thin films formed by different film formation methods have different molecular aggregation states. [ABSTRACT FROM AUTHOR]

Thermally evaporated of zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP) organic thin films have been successfully prepared and investigated. X-ray diffraction patterns of fresh grown and annealed ZnTPyP thin films have been performed. Spectra of transmission (T) and reflection (R) have been measured and have been used to establish optical constants and relevant dielectric variables. The absorption spectrum of pristine and annealed ZnTPyP films shows the most intense band called Soret band (B) which reveals Davydov splitting into two peaks Bx and By. Furthermore, two quasi-electronic bands named Q-bands and another weaker band labelled N have been observed at UV–visible spectral region. To derive several dispersion parameters of the studied ZnTPyP films, a single oscillator theory is implemented to the normal behaviour portion of the n-spectra whereas K-spectra is used to deduce the coefficient of absorption and the optical gap energies. Many optical aspects have also been discussed, such as dielectric constants, optical conductivity and energy loss functions (SELF and VELF). Optical constants, dispersion parameters and energy loss functions of ZnTPyP thin films have shifted with the thermal annealing range up to 523 K, which could be considered in design the energy conversion and storage devices based on ZnTPyP thin films. [ABSTRACT FROM AUTHOR]

The article evaluates several member news briefs. Topics include examines that SCI America International group awarded the 2021 Perkin Medal to Jane Frommer as the 114th Perkin Medal was presented to Jane at the Bellevue Hotel in Philadelphia, Pennsylvania, on September 14, 2021 in recognition of her outstanding contribution to chemistry.

As the cost of electronics decreases, the demand for short‐term and single‐use applications, such as smart packaging, increases. Consequently, there is significant need for electronically active biodegradable materials to reduce the environmental impact of disposable electronic devices. A bilayer dielectric is developed based on environmentally friendly, low‐cost solution‐processable polymers, fabricated by thermally crosslinking a toluene diisocyanate‐terminated polycaprolactone (TPCL) layer with the hydroxyl groups of a poly(vinyl alcohol)/cellulose nanocrystal (CNC) blended dielectric (PVAC). Metal–insulator–metal (MIM) capacitors are fabricated and characterized under ambient and humid conditions. The incorporation of a TPCL layer in the bilayer dielectric results in a large reduction in moisture sensitivity when compared to neat PVAC without significantly altering the dielectric constant. When utilized as a dielectric in organic thin‐film transistors (OTFTs), the transistors prepared with the PVAC/TPCL dielectric have greater on/off ratios and hole mobilities, with reduced hysteresis compared to devices fabricated with PVAC. Furthermore, the fabricated OTFTs function at operating voltages six times lower when compared against a traditional silicon dioxide (SiO2) dielectric. The facile processing, combined with superior device performance, makes this green bilayer dielectric a promising candidate material for biodegradable disposable electronic applications. [ABSTRACT FROM AUTHOR]