Phthalocyanine Thin Films Research Articles

Impact of gamma irradiation on optical and nonlinear properties of Indium chloride phthalocyanine thin films

This study investigates the impact of gamma radiation on indium chloride phthalocyanine (lnPcCl) thin films, which were prepared via vacuum thermal evaporation. x-ray diffraction revealed the amorphous structure of the films, with increasing gamma doses causing more noticeable structural disorders. Optical analysis showed a slight decrease in the optical band gap energy and a significant reduction in the fundamental band gap energy. Additionally, higher gamma doses led to decreased transmittance and increased reflectance. The study also observed substantial enhancements in nonlinear optical parameters, such as third-order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n 2). These findings suggest the potential of gamma-irradiated lnPcCl films for advanced optoelectronic and nonlinear optical applications.

Physical Properties Studies of Magnesium Phthalocyanine (MgPc) Thin Films of Different Annealing Temperatures Prepared by Pulsed Laser Deposition Technique

Magnesium Phthalocyanine (MgPc) was deposited on a glass substrate by pulsed laser deposition (PLD) using Q-Switching Nd:YAG laser with wavelength 1064 nm, repetition rate 6 Hz, at room temperature (300K) and different annealing temperatures (373, 473, and 573)K under vacuum condition of 10-3 torr. All films were annealed for one hour to attain crystallinity. X-ray diffraction (XRD) of MgPc powder indicated that MgPc crystallizes in polycrystalline with a monoclinic structure. While comparing the MgPc films, it was observed that the intensity of the characteristic peak increases with temperature, and the crystallization exhibited a monoclinic structure typical of the β-form. The Miller indices, hkl, values for each diffraction peak in the XRD spectrum were calculated. The characteristic peak of Phthalocyanine (MgPc) was found at 2θ value 6.9137ᵒ with the hkl value of (100) for both MgPc powder and deposited thin films. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) analyses indicated that crystallinity improved and surface morphology was enhanced with the rise in annealing temperature and showed uniform-sized grains. They also assisted in identifying the optimal parameters that yielded the best structural properties for the film. The optical properties of MgPc thin film showed two absorption bands. The MgPc thin films exhibit transport and onset direct energy gaps (Eg) for all samples. Additionally, the absorption coefficient (α) was calculated using Lambert Law, revealing a slight dependence on the annealing temperature.

Investigation of CdSe quantum dots embedded in copper phthalocyanine thin films

Investigation of CdSe quantum dots embedded in copper phthalocyanine thin films

Edge-on orientation of thermally evaporated metal phthalocyanines thin films for humidity sensing application

Edge-on orientation of thermally evaporated metal phthalocyanines thin films for humidity sensing application

Investigation of the structure-transport correlation in metal phthalocyanine thin films

Investigation of the structure-transport correlation in metal phthalocyanine thin films

Effect of annealing on the molecular ordering and crystal structure of iron phthalocyanine thin films on Si (111) surface

The Effect of annealing on molecular ordering in Iron Phthalocyanine (FePc) thin films deposited on Si (111) substrate surface was investigated using lab source (Cu Kα) based x-ray diffraction, synchrotron based 2-dimensional grazing incidence x-ray diffraction, polarization dependent x-ray absorption spectroscopy and hard x-ray photoelectron spectroscopy. Room temperature deposition of FePc on Si substrate resulted in amorphous thin films with randomly oriented FePc molecules. However, annealing of these amorphous films at 200°C led to crystallization with highly ordered FePc molecules having monoclinic crystal lattice structure. The ordered FePc molecules followed edge-on stacking on Si substrate surface with an azimuthally averaged tilt angle of 75±5° between molecular plane and substrate surface. Also, the b-c plane of the unit cell was lying almost parallel to the substrate surface. The edge-on stacking ordering of FePc molecules in annealed thin films led to higher charge conduction as compared to as-deposited films.

Optical and morphological characterization of erbium phthalocyanine thin films on unpolished/polished substrates for enhanced solar water heating efficiency

Optical and morphological characterization of erbium phthalocyanine thin films on unpolished/polished substrates for enhanced solar water heating efficiency

Molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires

The development of molecular magnets plays a major role in emerging organic spintronics applications, as it exhibits both semiconducting and magnetic properties. Herein, we report on the molecular-orientation-dependent magnetic properties of iron phthalocyanine (FePc) thin films and microwires. FePc thin films grown on SiO2 and flexible kapton substrates clearly reveal that the morphology is strongly influenced by the substrates and film thickness. Meanwhile, the molecular stacking orientation of FePc thin films can be tuned by 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) templating layer and film thickness. Magnetic hysteresis loops show that the iron atoms are strongly magnetically coupled into ferromagnetic chains at low temperature with high coercivity at 1000 Oe. The magnetization and susceptibility of FePc thin films are dependent on the molecular orientation, and the Curie–Weiss constant is modulated from 24 ± 2 K K to 35 ± 2 K through the templating effect, in which the molecular stacking orientation changes from standing-up to lying-down arrangement. Furthermore, strong orientation dependent ferromagnetism is also observed in low-dimensional η-FePc microwires, in which the Curie–Weiss constants change from 20 ± 2 K to 35 ± 2 K when magnetic field rotated from short wire axis to long wire axis. The ability to fabricate FePc thin films on flexible substrate with controllable molecular orientation and ferromagnetism makes them promising candidates for flexible spintronic devices.

Phthalocyanine thin films on Si(111)

The growth of organic films on silicon represents a very interesting and up-to-date field of research in both fundamental science and in regard of possible applications. As silicon still is the element of choice in semiconductor technology, methods to modify the properties of silicon surfaces become increasingly important with a modification by organic overlayers representing a very promising approach. Phthalocyanines represent a family of semiconducting molecules based on a π-conjugated macrocycle ring and are already successfully employed in various applications, e.g. in (opto-)electronic devices. In addition, their structure and therewith their properties can be easily modified at various positions, making them ideal candidates for tailor-made silicon surface modifications. Regarding Si(111), a variety of different phthalocyanines on clean and modified surfaces was investigated within the last decades. In the current review, an overview on these works is presented.

Investigating the properties of nano crystalline beta metal-free phthalocyanine films: From molecules to optoelectronic applications

A study was conducted to investigate the structural and optical properties of nanocrystalline beta metal-free phthalocyanine (β-H2Pc) thin films using computational and experimental methods. DFT calculations using the B3LYP basis set 6–311G were performed to predict the HOMO-LUMO gap of the β-H2Pc (2.13 eV). The crystalline structural properties of the β-H2Pc were examined through XRD analysis, which revealed that the powder β-H2Pc had a monoclinic polycrystalline structure, while the β-H2Pc thin film was amorphous. Various methods were used to determine and compare the average crystallite size and microstrain, with the size-strain plot method yielding an average crystallite size and microstrain size of 73.15 nm and 0.0051, respectively. Using SEM to analyze the film's surface topography, the mean grain size was found to be 0.85 µm due to agglomeration. Linear and nonlinear spectrophotometric measurements were employed to examine the optical properties of the β-H2Pc thin film. The film exhibited indirectly permitted inter-band transitions, with the onset and fundamental band gaps of 1.51 eV and 2.74 eV, respectively. Furthermore, several absorption and dispersion characteristics for thin films were identified. The properties exhibited by Au/β-H2Pc/p-Si/Al heterojunction indicate its potential suitability for photosensor applications.

Phthalocyanine-Based Organic Thin Film Transistors as a Platform for Cannabinoid Sensors

With a growing international trend of Cannabis legalization, there is a present need for on-the-spot, low cost, and rapid differentiation of cannabinoids. The two primary cannabinoids, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), obtained from Cannabis, elicit very different pharmacological effects necessitating consumer and industry methods for their detection and rapid speciation. CuPc and F16-CuPc, well characterized p- and n-type semiconductors respectively, are used as the OTFT semiconducting layer in combination with a cannabinoid-sensitive chromophore allowing for the differentiation of THC and CBD. Device analysis of pre- and post-pyrolyzed rapid plant extract samples was able to predict the THC/CBD ratio with HPLC accuracy. Spectroelectrochemistry was used to probe molecular interactions between cannabinoids with and without a cannabinoid sensitive chromophore against a variety of Pcs. Spectroelectrochemical changes to the Q-band region of the Pc spectra in the presence of analytes was related to modified ratios of Pc-Pc orientations in solution, streamlining material selection, reducing manufacturing burden, and expediting sensor development. 2D-NMR was used to further elucidate unique Pc-Pc and Pc-analyte interactions, providing additional insight on atomic level interactions. Through altered Pc-Pc orientations, analytes can induce physical alterations to Pc thin-film morphology and structure, consequently, modifying electrical performance beyond charge trapping effects. Pc peripheral and axial substitutions allow an additional level of Pc tunability and their relationship with analyte interactions, film structure, and OTFT sensing performance was explored.We established relationships between thin-films of phthalocyanines (Pcs) with a variety of central, peripheral, and axial substituents and their response to THC. X-Ray diffraction and UV–vis absorption spectroscopy measurements demonstrate significantly altered film morphologies and the formation of new crystal orientations in response to analytes, which are corroborated by scanning electron microscopy. With exposure to THC, aluminium chloride Pc generates the largest physical film changes as well as the largest changes in OTFT performance. These findings have implications for Pc-based OTFT sensor design, suggesting that the semiconducting Pc thin-film morphologies are not static in the presence of analytes, and that the sensing response is driven both by strong analyte-Pc coordination and bulk film restructuring to accommodate these interactions.References Advanced Functional Materials, 2021, ASAP, doi:10.1002/adfm.202107138ACS Appl. Mater. Interfaces, 2020, 12, 45, 50692–50702ACS Sensors, 2019, 4, 10, 2706-2715. Figure 1

Electrical, optical and morphological properties of Au/n-Ge heterostructures by using cobalt phthalocyanine (CoPc) interlayer

The morphology of CoPc thin films on n-Ge substrate characterized using AFM measurements shows fairly smooth surface with RMS roughness of 8.42 nm. Structural analysis of cobalt phthalocyanine (CoPc) thin films is confirmed using Raman measurements at 785 nm excitation wavelength with three vibrational modes at 1539 cm−1 resembles the C-N bond and 755 cm−1, 685 cm−1resembles to C-C bonds. The EDS spectrum of the Au/CoPc/n-Ge surface reveals the presence of elements contributing the structure of CoPc. Optical properties of CoPc thin films described with a Q band splitting between 600 to 700 nm with an optical bandgap of 3.8 eV The electrical measurements of Au/n-Ge Schottky heterostructures with CoPc interlayer reveals that the barrier height parameters are significantly improved than without interlayer. Low series resistance values of heterostructures than pristine contact shows its applicability in efficient photovoltaic cells. The conduction mechanisms of these contacts are evaluated using forward current-voltage properties. At moderately high forward voltages, the transport properties of Au/CoPc/n-Ge heterostructures are truly dominated by trap charge limited current (TCLC) mechanism. The photodiode properties of CoPc/n-Ge heterostructures were investigated at 775 nm wavelength and the responsivity and detectivity of the contacts found to be varied with reverse voltage.

Features of obtaining and properties of thin films organic semiconductors

In recent decades, thin films of organic semiconductors (OS), or, as they are also called, organic molecular crystals, have attracted special attention in connection with a number of proposals for their use in functional units of modern electronics, and therefore in modern technological equipment. At the same time, the optical, electrophysical and photoelectric properties of OS are very important, which are determined both by the structure of organic molecules, that is, the starting material, and by the crystal structure of condensates, that is, by the technological conditions of film production. In this regard, this article presents the results of studies of some properties of OS and the technology of obtaining thin films based on them. OS are characterized by weak intermolecular bonds of the Van der Baals type, which causes the low energy of their crystal lattice. In this regard, the electronic structure of individual molecules during the formation of a crystal does not change significantly, and the properties of the crystals almost completely preserve the individual features of the molecules in combination with new properties caused by their collective interaction. This determines the main features of optical and electrophysical properties of OS, their energy structure of neutral and ionized states. In this article, it is experimentally confirmed that the planar structure of atoms of molecular crystals, in particular, linear acenes, and therefore the number of π-electrons responsible for exciton absorption in the visible region of the spectrum determines the position of the edge of their own optical absorption. It was also confirmed that the long-wavelength shift of the optical absorption edge of thin films of phthalocyanines is observed when atoms of heavy elements, for example, lead, are introduced into the molecule. When atoms of lighter elements are introduced into the phthalocyanine molecule, their planarity is not disturbed, and the long-wavelength shift of the edge is much smaller. An explanation of such changes is presented based on the interaction of foreign atoms with the π-electron system of phthalocyanine rings of neighboring molecules. The significant influence of the technological parameters of production, in particular the temperature of the substrate during thermal sputtering, on the crystal structure and optical properties of thin films of linear polyacenes and metallophthalocyanines has been demonstrated and substantiated. The possibility of controlling and presetting the necessary properties of thin-film condensates of molecular crystals is shown.

Symmetry-breaking charge transfer and intersystem crossing in copper phthalocyanine thin films.

Intermolecular interactions in π-stacked chromophores strongly influence their photophysical properties, and thereby also their function in photonic applications. Mixed electronic and vibrational coupling interactions lead to complex potential energy landscapes with competitive photophysical pathways. Here, we characterize the photoexcited dynamics of the small molecule semiconductor copper pthalocyanine (CuPc) in solution and in thin film, the latter comprising two different π-stacked architectures, α-CuPc and β-CuPc. In solution, CuPc undergoes ultrafast intersytem crossing (ISC) to the triplet excited state. In the solid state, both α-CuPc and β-CuPc morphologies exhibit a mixing between Frenkel and charge-transfer excitons (Frenkel-CT mixing). We find that this mixing influences the photophysical properties differently, based on morphology. In addition to ISC, α-CuPc demonstrates symmetry-breaking charge transfer, which furthermore depends on excitation wavelength. This mechanism is not observed in β-CuPc. These results elucidate how molecular organization mediates the balance of competitive photexcited decay mechanisms in organic semiconductors.

Influence of Heat Treatment on Surface, Structural and Optical Properties of Nickel and Copper Phthalocyanines Thin Films.

The work presents the effect of annealing on the change of polycrystalline α and β phases of copper and nickel phthalocyanines. We have found that this process has a great influence on the optical properties of the vapor-deposited layers. The performed measurements showed that for various forms of MPc, the values of the refractive index and the extinction coefficient increased, and consequently, so did the absorption coefficient. The AFM images taken showed that the values before and after heating are morphologically different. Raman measurements showed that the band at about 1526 cm−1 (B1g symmetry) has higher intensity for the α form than for the β form. The intensity of this band is related to changing the form of phthalocyanine from α to β. Our measurements have shown that by changing the annealing temperature of the layers, we change their optical properties. As a consequence, we change their optoelectronic parameters, adjusting them to the requirements of new optoelectronic devices, such as solar cells, sensors, displays and OLEDs.

Classification of VOC Vapors Using Machine Learning Algorithms

Detection of volatile organic compound (VOC) vapors, which are known to have carcinogenic effects, is extremely important and necessary in many areas. In this work, the sensing properties of a cobalt phthalocyanine (CoPc) thin film at six different VOC vapors (methanol, ethanol, butanol, isopropyl alcohol, acetone, and ammonia) concentrations from 50 to 450 ppm are investigated. In this sense, it is observed that the interaction between the VOC vapors and the CoPc surface is not selective. It is shown that using machine learning algorithms the present sensor, which is poorly selective, can be transformed into a more efficient one with better detection ability. As a feature, 10 seconds of responses taken from the steady state region are used without any additional processing technique. Among classification algorithms, k-nearest neighbor (KNN) reaches the highest accuracy of 96.7%. This feature is also compared with the classical steady state response feature. Classification results indicate that the feature based on 10 seconds of responses taken from the steady state region is much better than that based on the classical steady state response feature.

Copper Phthalocyanine MWCNTs Composites: Characterization and Evaluation for Sensor and Solar Cells interlayer

Copper Phthalocyanine (CuPc) thin film with and without multi-walled carbon nanotubes (MWCNTs) is prepared using the solution based method and used in gas sensor and solar cell applications. The structural characteristics of the CuPc thin films showed a single peak around 7o with the preferred orientation for charge transportation. Using atomic force microscopy (AFM), morphological properties show a rough surface with some aggregates and ribbons. The optical absorption properties were determined using UV-Visible absorption spectroscopy; the optical band gap has varied after adding MWCNTs to CuPc. Electrical conductivity of CuPc:MWCNTs composite is higher than that of the pure CuPc. The CuPc thin film sensr have shown good response properties to ammonia gas. The solar cell performance of the P3HT:PCBM based solar cell was enhanced.

Variation in zinc phthalocyanine molecular orientation on SrTiO3(100) surface

The molecular orientation of zinc phthalocyanine (ZnPc) thin films grown on SrTiO3(100) substrate was studied using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results revealed that the molecular orientation changed with the deposition of ZnPc. At the deposition of 0.4 monolayer equivalent (MLE), the π* resonance at grazing incidence was more prominent than that at normal incidence, indicating a lying configuration. By comparing the experimental results with theoretical calculations, the molecular orientation angle for the ZnPc ultrathin film was estimated to be 30°. During the deposition upto 4.3 MLE, the orientation angle increased with increasing ZnPc molecular density in the layer and reached 61°, which is close to that of the α-crystalline films. The dependence of the molecular orientation on the deposition amount indicates that the molecular orientation in the ZnPc ultrathin films is governed by the ZnPc molecular density on the SrTiO3(100) substrate surface.

Structural, optical and DFT studies of disodium phthalocyanine thin films for optoelectronic devices applications

Theoretical and experimental investigations have been carried out on the structural and optical properties of disodium phthalocyanine (Na2Pc) thin films prepared using the thermal evaporation method. The optimized geometry structure, vibrational bands and HOMO-LUMO gap were predicted by density functional theory (DFT) computations. FTIR and XRD techniques were utilized to analyze the structural characteristics of Na2Pc thin films. XRD exhibited that the Na2Pc powder has α-polycrystalline nature with a triclinic structure, whereas the Na2Pc thin films have an amorphous structure. The optical properties of different thicknesses films were studied in the wavelength range of 200–2500 nm using the UV–Vis-NIR spectrophotometer. The absorption coefficient of the Na2Pc molecules showed four absorption bands in the UV–Vis region. The types of optical transitions were determined by applying the energy band model as an indirect allowed transition. The onset gap, optical gap and Urbach energy were estimated to be 1.31, 2.25 and 0.41 eV, respectively. The results of absorption coefficient and energy gap showed that the Na2Pc thin films can be utilized in optoelectronic device applications. The absorption index, k, and refractive index, n, were determined and found to be independent of the film thickness. The dispersion parameters have been evaluated according to a single oscillator model in the non-absorbing region of the spectrum.

Mode-locked ytterbium-doped fiber laser with zinc phthalocyanine thin film saturable absorber

A stable mode-locked laser was demonstrated using a newly developed zinc phthalocyanine (ZnPc) thin film as passive saturable absorber (SA) in ytterbium-doped fiber laser (YDFL). The ZnPc thin film was obtained using a casting method and then inserted between the two fiber ferrules of a YDFL ring cavity to generate mode-locked pulses. The resulting pulsed laser operated at a wavelength of 1034.5 nm having a repetition rate of 3.3 MHz. At pump power of 277 mW, the maximum output power and pulse energy are achieved at 4.92 mW and 1.36 nJ, respectively. ZnPc has a high chemical and photochemical stability, and its significance for use as a potential SA in a mode-locked laser is reported in this work.Graphical