Copper Phthalocyanine Thin Films Research Articles

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.

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.

Carrier mobility in field effect transistors based on copper-phthalocyanine thin films with different phase structure

Using annealing procedure at different temperatures after deposition at room temperature we obtained copper- phthalocyanine (CuPc) thin films with a — and p —phase structure. A phase structure of thin films was controlled by X-ray diffraction method, morphology was controlled by SEM. The field effect transistors was fabricated by high vacuum deposition of CuPc thin film (thickhess of 100 nm) on Si02 substrate which acting as gate contact. Gold drain and source contacts deposited on the top of active layer of FET. From measured current voltage measurements calculated mobility and concentration of charge carriers in FET. These parameters depend on phase structure of CuPc thin film, and characteristics of our FET are comparable with values of other authors.
 CuPc is commercially available macro cyclic metal complex that can be easily obtained in large quantity and high purity. Together with other phthalocyanine derivatives, the chemically and thermally stable CuPc has wide applications in dye processing, spectral sensitization, chemical sensors, and optical data storage [3-4]. The semiconducting behavior of metal phthalocyanines was first observed in 1948 and they have since attracted great interest in advancement of protptype organic semiconductors. Among the metal substituted phthalocyanines CuPc has been found superior properties [5-7], such as phenomena of field dependent and wavelength-dependent efficiency in an organic static induction transistors, and stabilizing role of CuPc layer on a highly stable organic electroluminescent device based on thin film Alq, and indicated a very weak interaction between CuPc and Au at the interface.
 In general, phthalocyanine materials can exist in several crystalline polymorphs, including a-, p -, x-and y - structure, and the most well known are the thermally metastable a- and p - [8-10], Phthalocyanine films deposited at room temperature usually consist of a-phase crystallites (at sublimation pressure of less than 10 Pa). At higher deposition pressures or at substrate temperature above 210°C, the p -phase directly obtained [11], Although it is well known that a-phase crystallites undergo a phase transformation into P -phase by treatment in various organic suspension media [12,13] or during annealing at higher temperatures [14,15], only some authors describe the nature of the a—>p phase transformation of copper phthalocyanine thin films with a thickness of less than 100 nm [8,14-15].

Photoluminescence of organic thin film Copper phthalocyanine CuPc for LED application

This work falls into the theme of studying energy efficient organic Light Emitting Diodes (organic LEDs) by relying on optical techniques. Our aim is to take a deeper look into the emission in the near infrared region after visible excitation, of copper phthalocyanine thin film deposited on glass by physical vapor deposition, using photoluminescence spectroscopy (PL), in order to use the latter as a hole injection layer or emissive layer in organic LEDs and consequently to enhance its efficiency.

Directly Probing Interfacial Coupling in a Monolayer MoSe2 and CuPc Heterostructure.

It is of great importance to develop useful methods to evaluate interfacial coupling strength noninvasively for exploring and optimizing heterointerface functionality. Recently, organic-inorganic van der Waals (vdW) heterostructures (HSs) composed of organic semiconductors and transition-metal dichalcogenides (TMD) have shown great potential for developing next-generation flexible optical, electrical, and optoelectrical devices. Since vdW coupling dominates the property of such a vdW HS, it is crucial to develop a method to evaluate its interfacial coupling strength noninvasively. In this work, by combining electrical force microscopy (EFM) and Raman and photoluminescence spectroscopic measurements, we were able to directly probe the coupling strength between monolayer MoSe2 and a copper phthalocyanine (CuPc) thin film. Especially, we also found a new Raman mode in HS due to the Davydov splitting of the CuPc thin film via strong interfacial coupling between the two materials. This new Raman mode was thus utilized as a probe to reveal the modulation of the coupling strength by changing post-treatment conditions. All of these results indicate that the method developed here is capable of evaluating the coupling strength of the MoSe2/CuPc HS effectively and innovatively, which aids in providing deep insights into such hybrid vdW HSs for future optical and optoelectrical applications.

Thin film growth of phase-separating phthalocyanine-fullerene blends: A combined experimental and computational study

Blended organic thin films have been studied during the last decades due to their applicability in organic solar cells. Although their optical and electronic features have been examined intensively, there is still lack of detailed knowledge about their growth processes and resulting morphologies, which play a key role for the efficiency of optoelectronic devices such as organic solar cells. In this study, pure and blended thin films of copper phthalocyanine (CuPc) and the Buckminster fullerene (C60) were grown by vacuum deposition onto a native silicon oxide substrate at two different substrate temperatures, 310 K and 400 K. The evolution of roughness was followed by in-situ real-time X-ray reflectivity. Crystal orientation, island densities and morphology were examined after the growth by X-ray diffraction experiments and microscopy techniques. The formation of a smooth wetting layer followed by rapid roughening was found in pure CuPc thin films, whereas C60 shows a fast formation of distinct islands at a very early stage of growth. The growth of needle-like CuPc crystals loosing their alignment with the substrate was identified in co-deposited thin films. Furthermore, the data demonstrates that structural features become larger and more pronounced and that the island density decreases by a factor of four when going from 310 K to 400 K. Finally, the key parameters roughness and island density were well reproduced on a smaller scale by kinetic Monte-Carlo simulations of a generic, binary lattice model with simple nearest-neighbor interaction energies.

Polymorphism and structure formation in copper phthalocyanine thin films.

Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group C2/c) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group P 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence. The unit-cell parameters and the space group were determined by kinematic scattering theory and provide possible molecular arrangements within the unit cell of the C2/c structure by excluded-volume considerations. In situ X-ray diffraction experiments and ex situ atomic force microscopy complement the experimental data further and provide insight into the formation of a smooth thin film by a temperature-driven downward diffusion of CuPc molecules during growth.

Effect of organic solvent vapor treatment on transistor performance and contact resistance of copper phthalocyanine based organic field-effect transistors

In this study, we investigated the effect of organic solvent drop-casting and solvent vapor annealing (SVA) on the surface morphology of copper phthalocyanine (CuPc) thin film and its effect on contact resistance in organic field effect transistors (OFETs). Organic solvents: acetone and isopropyl alcohol (IPA) are used for drop-casting and SVA treatment of CuPc film. The morphology, crystallinity and optical properties of untreated and treated CuPc films are investigated through ultraviolet–visible (UV–Vis) absorption spectroscopy, X-ray diffraction (XRD) and atomic force microscopy (AFM). The results reveal that crystallinity and grain size increase in CuPc film treated with SVA. Large grain size results fewer grain boundaries forming better contact between source/drain (S/D) electrodes and the organic layer. As a result, the SVA treated CuPc based OFETs show one order increased charge carrier mobility and two order decreased contact resistance compared to that observed in untreated CuPc based OFET.

Photoresponse characteristics from vacuum deposited thin film of copper phthalocyanine: dependence on grain size

An organic photodetector (PD) is fabricated with single layer thin film of copper phthalocyanine (CuPc) on glass substrate. The thermal deposition of CuPc film on the substrate was realized under high vacuum and at different substrate temperature (room temperature, 40 ◦C, 70 ◦C, 100 ◦C). The comparison of photoresponse characteristics of CuPc thin film deposited under different conditions showed good improvement with increase in the substrate temperature, and the best performances being observed for the film deposited at substrate temperature of 100 ◦C. The thin film of CuPc characterized through X-ray diffraction (XRD) spectroscopy and atomic force microscopy (AFM) clearly indicated that with increase in substrate temperature, the grain size of CuPc film increased, which improved the crystallinity and hence the photoconductivity of the device. The CuPc thin film based PD displayed stable and reproducible photoswitching characteristics under white light irradiation, with photocurrent modulation by varying in input optical power. The highest photo to dark current ratio and responsivity of the devices was calculated to be, ca. 6.5 and 7.1 mA-W−1 at low optical power, ca. 14.5 mW-cm−2.

Spectral-kinetic properties of transient absorption of hybrid silver–copper phthalocyanine nanostructures

In this paper, we studied the dynamics of transient absorption spectra of a hybrid nanostructure (Ag–CuPc)6 Ag based on island silver films and copper phthalocyanine thin films, as well as individual structural units of this system, by femtosecond transient absorption spectroscopy. It is found that the effects observed for a hybrid nanostructure reflect the existing mutual influence of the plasmonic and organic subsystems on the spectral-kinetic characteristics of each other. The characteristic time of the main component of induced optical density kinetics at a wavelength λ = 525 nm (τ ~ 15 ps) that is caused by singlet-triplet relaxation of the excited electronic states of the organic subsystem of the hybrid structure is noticeably shorter than the relaxation time (τ ~ 50 ps) at the same wavelength for a pure copper phthalocyanine film of 40 nm thickness, just the same as the total thickness of the organic subsystem in the hybrid structure. It is assumed that the presence of silver nanoparticles in the hybrid structure (Ag–CuPc)6 Ag, affects the probability of intersystem conversion in the organic subsystem, accelerating the transition of CuPc molecules to a long-lived triplet state due to a strong local field near the surface of the plasmon particle. The triplet-triplet absorption spectrum of copper phthalocyanine in the spectral range 470–750 nm was obtained.

Pump-Probe Technique to Study of the All-Optical Switching Properties of Copper Phthalocyanine Thin Film prepared via Pulsed laser deposition

Z-scan has been utilized for studying the non-linear properties and optical limiting behaviors of the dye Copper Phthalocyanine thin films. The refractive index is negative, which indicates a self-defocusing behavior and non-linear absorption coefficient (β) of CuPc is a positive sign is a result of RSA. The optical switching behaviors of dye have been researched with the use of the method of the pump-probe with 9ns Q-Switched Nd: YAG laser at pump beam equal to 532 nm and a probe beam equal to 630nm Diode laser. The thin films of copper Phthalocyanine also reflect a significant limiting of the optical power of CW laser with an adequate threshold of the optical limiting. The dye’s switching behavior is a result of the probe beam’s excited-state absorption (ESA) with the molecules of the dye. The modulation of the probe beam with the increase of intensity of the pump has been researched as well.

MACROCYCLE RING AND PERIPHERAL GROUP SIZES-DEPENDENT VAPOR SENSING PROPERTY OF COPPER PHTHALOCYANINE THIN FILMS

Spin-coated thin films of copper phthalocyanine (CuPc) were fabricated using different rotation speeds from 250 rpm to 1250 rpm. The structural characterization of these films was analyzed using UV-vis spectroscopy and atomic force microscopy (AFM). Gas sensing properties of these spun thin films were investigated against different volatile organic compounds such as chloroform, dichloromethane and toluene using surface plasmon resonance (SPR) technique. CuPc thin films were found to be highly sensitive to chloroform and dichloromethane vapor with fast response and recovery times. These measurements clearly indicated that the CuPc molecule is a promising material for the development of the room temperature vapor sensing applications with sensitivities between [Formula: see text] and [Formula: see text] percent response ppm[Formula: see text]. Three different functional groups of CuPc structures coded as CuPc I, II and III were investigated which differ from each other in their chemical structures in terms of their microcycle ring groups and peripheral groups, all attached to the same free base porphyrin skeleton. The number of microcycle ring groups and peripheral groups were found to be efficient on the gas sensing properties. The calculated refractive index and extinction coefficients using SPR curves were [Formula: see text] for CuPc I thin film, [Formula: see text] for CuPc II thin film and [Formula: see text] for CuPc III thin film, respectively. For different substrate rotation speeds, the thin film thicknesses vary between 2[Formula: see text]nm and 6[Formula: see text]nm for CuPc I and CuPc III thin films whereas it ranges between 4[Formula: see text]nm and 9[Formula: see text]nm for CuPc II thin film.

Growth of Cu phthalocyanine thin films on Sb passivated vicinal Si(111) with molecular columns parallel to the surface

This study shows a growth of copper phthalocyanine (CuPc) thin films with one-dimensional structures parallel to the surface on Sb-passivated stepped silicon surfaces with (111) orientation. Sb passivation maintains all the step and terrace features on the vicinal Si(111) surface, where subsequently a CuPc sub-monolayer is deposited. The CuPc forms islands of sub-micrometer extension, which shows substantial molecular diffusion on the surface after deposition. In a single island of CuPc, one-dimensional columns of stacked CuPc molecules grow parallel to the step edges of the vicinal Sb–Si(111) surface, which illustrates the strong anisotropy of molecular growth induced by the stepped surface. The self-assembly behavior of CuPc indicates that the Sb passivated surface allows high molecular mobility of CuPc, having anisotropy effect from the stepped substrate structure.

Chipless RFID Tag With Enhanced RCS Used as a Phthalocyanine-Based Solvent Vapors Sensor

A novel uniplanar chipless RFID solvent vapors/gas sensor is proposed in this letter. The sensor etched on an extremely thin capton substrate is composed of the folded dipole resonator loaded by the interdigital capacitor located inside the planar rectangular metallic loop that improves the radar cross section (RCS) response. When illuminated by a plane wave, the folded dipole causes a notch in the RCS response of the loop located near its resonant frequency. The high RCS level (-18 dBsm), together with the notch depth (16 dB) assure a reliable detection of its position within the frequency dependence of RCS curve. In order to enhance the structure sensitivity to the presence of acetone vapors, the tetrasulfonated copper phthalocyanine thin film was applied as a sensitive layer during the process of folded dipole metallization. The experimental verification confirmed the viability of sensor proof-of-concept for the detection of chemical vapors.

Effect of Annealing Induced Morphology on Mobility of Copper Phthalocyanine Thin Films

Post deposition annealing of copper phthalocyanine (CuPc) films develops nano-rod structures on the surface of the film and the length and uniformity of nano-rods depend on the annealing temperature. The proposed methodology combines scanning electron microscopy (SEM) and atomic force microscopy (AFM) with impedance spectroscopy to give new insights into the influence of thermally developed nano structures on the charge carrier mobility of CuPc films. The impedance spectroscopy provides a non-invasive and cost-effective study which finds that the hole mobility of CuPc films improves upon increasing annealing temperature, reaches maximum of (5.3 ± 0.7) × 10–5 cm2V−1 s−1 at 150 °C and reduces at higher temperatures. These results will benefit future strategies for the surface modification of small molecular films for improved charge transport in organic and hybrid devices.

Thin films of copper phthalocyanine deposited by solution processing methods

Abstract In this work, we show and discuss the surface structure picture of copper phthalocyanine (CuPc) thin films deposited from trifluoroacetic acid (TFA) solvent onto silicon substrates at ambient conditions by four solution processing methods, namely drop-casting, dip-coating, spin-casting and spray-coating. The CuPc films were studied by AFM, as the main technique, and complemented by micro-Raman spectroscopy. Essentially, such thin films consist of CuPc molecular nanoribbons of a fixed ~1 nm thickness. CuPc molecules are arranged in an in-plane direction and formed in stacks under a defined tilt angle with respect to the substrate surface (monolayer) or underlying CuPc layer (multilayer). The film morphology takes various forms depending on the solution concentration, number of layers, and the deposition method. For instance, the morphology varies from very wide (~600 nm) but flat (~1 nm) ribbons for films prepared by dip-coating to crystallized rod-like features (multi-layered ribbons) when obtained by spray-coating. The factors studied in this paper should be taken into consideration in designing and controlling the criteria for rigorous CuPc film architecture.

Study the Nonlinearity Characteristics of Organic-Semiconductor (CuPc) Prepared Via Pulsed Laser Deposition Technique with Different Thickness

The optical absorption spectrum, Photoluminesces, and non-linear optical properties for Copper Phthalocyanine (CuPc) thin films (150,300 and 450 nm) respectively have been investigated via pulsed laser deposition technique. The absorption spectrum indicted that there are two bands one in UV around 330 nm which called B-band and the second in Visible around 650nm which called Q-band. Photoluminescence spectrum related to deposit samples has been determined with different thicknesses. From closed and open aperture Z-scan data non-linear absorption coefficient and non-linear refractive index have been calculated respectively using He-Ne laser which have beam waist of (24.2 μm), wave-length of (632.8 nm) and Rayleigh thickness was 2.9 mm. Through dividing closed by open apertures, non-linear refractive index was calculated accurately. Finally, the study also showed the suitability of the deposited films as an optical limiter at the wavelength 632.8 nm.

Effect of applied electric field on growth morphology of copper phthalocyanine thin films

The effect of electric field on the initial stages of copper phthalocyanine adsorption on the SiO2 substrate was studied experimentally. The external electric field was applied during thermo-vacuum evaporation of CuPc. Using atomic-force microscopy and scanning electron microscopy, it was found that in the presence of an electric field, the film morphology changes. Instead of randomly oriented elongated crystallites, new form bend-shaped ones are formed on the substrate surface. The paper provides an explanation of the experimentally observed effect of the electric field on the structure of the growing film.

Experimental and density functional theory study on humidity sensing properties of copper phthalocyanine (CuPc)

The quartz crystal microbalance (QCM) technique was applied to investigate humidity sensing properties of a copper phthalocyanine (CuPc) thin film prepared by drop cast method. The humidity adsorption and desorption kinetics of (CuPc) thin film was evaluated. The QCM and electrical measurements results showed that humidity sensing properties of CuPc is very sensitive to humidity changes and reversible adsorption/desorption performance which is an indicative of a good humidity sensor even at room temperature. Reproducible experimental results indicated that CuPc thin films have an abundant potential for humidity sensing applications at ambient temperature. According to the first-principle density functional theory calculations, the promising humidity sensing properties of CuPc can be attributed to the considerable charge transfer from the water molecule into Cu atom.

Physical properties of Cu and Dy co-doped ZnO thin films prepared by radio frequency magnetron sputtering for hybrid organic/inorganic electronic devices

Copper (Cu) and dysprosium (Dy) co-doped zinc oxide (ZnO) thin films were fabricated by radio frequency magnetron sputtering (RF-magnetron sputtering) using a homemade target having the atomic percentage of Cu and Dy of 1%, onto optical glass substrates and quartz substrates. The structural, morphological, optical, and electrical properties of fabricated ZnO:(Cu, Dy) structures were analyzed and discussed. It was found that all samples have hexagonal Würtzite structure. Optical transmission measurements indicate values larger than 75% in the 400–2500 nm ranges. The current-voltage characteristics of hybrid heterojunctions based on ZnO:(Cu, Dy) and poly(3-hexylthiophene-2.5-diyl) (P3HT) or copper (II) phthalocyanine (CuPc) thin films were acquired in the dark, in ambient atmosphere, and they exhibit the typical diode behavior, almost free of electrical hysteresis.