Observation of persistent photoconductivity in vanadyl phthalocyanine

Santos, Luiz Fernando dos; Faria, R.M.; Caño, Teodosio del; Saja, J.A. de; Constantino, Carlos J. L.; Amorim, Cleber A.; Mergulhão, S.

doi:10.1088/0022-3727/41/12/125107

Cited by 18 publications

(14 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It is generally accepted that β is related to the dimensionality of the charge transport process. In a 1D processes, 0 < β < 0.5, and in 3D processes, 0.5 < β < 1. , An average β value of 0.45 for our systems is consistent with 1D transport of electrons along the lengths of porphyrin cofacial assemblies via π–π interactions. , β varies linearly with temperature, while ln(τ) varies linearly with 1/ T . We interpret these T dependences as being due to activation barriers.…”

Section: Photoseponse Sensing and Mechanical Propertiessupporting

confidence: 78%

A Systematic Approach toward Designing Functional Ionic Porphyrin Crystalline Materials

Mazur

Hipps

2018

J. Phys. Chem. C

View full text Add to dashboard Cite

Synthetic ionic porphyrin self-assembled structures possess remarkable optoelectronic properties that are useful for energy and sensor related technological application, and there is a continued interest in tailoring their molecular structure and interactions in order to control their various functions. Central to these efforts is the fundamental understanding of the structure, the chemical and physical properties, and the relationship between the structural organization of the chromophores and their functions. In this Feature Article, we demonstrate the capability of a nucleation and growth algorithm to reproducibly synthesize nano- to millimeter size single crystals of several different ionic binary porphyrin (BP) systems under chemically controlled conditions. Single crystal X-ray diffraction analysis, morphology, sensing, and mechanical measurements are presented. UV–vis and X-ray photoelectron spectroscopy of these materials is also discussed. The crystalline porphyrin assemblies have varying degrees of dark conductivity (depending on their chemical and structural composition) but all appear to be sensitive to light; i.e., they absorb radiation and become conductive and/or persistently photoconductive (PPC). In addition, some of these crystalline porphyrins show persistent ion beam induced conductivity. This rich photo and ion response provides opportunities for the selective light control of these semiconductors. Exposure of the BP crystals to small gas molecules such as O2 strongly modifies their photocurrent in sensing experiments. The range of the Young’s modulus values extracted from nanoindentation experiments indicates that the BP crystals have a Young’s modulus intermediate between “soft” polymers and composite materials, making them excellent candidates for deformable optoelectronic devices. Both the experimental photoconductive and mechanical properties of the porphyrin self-assembled structures can be correlated with their molecular organization and morphology. In addition, quantum mechanical calculations provide the electronic band structure and the density of states and help explain experimental prompt photoconductivity measurements. Theory was also used to develop strategies for precise manipulation of the photoresponse of the BP crystals by selective structure modification. This work shows that combining the results from structural and theoretical studies and correlating them with electronic and optoelectronic properties can assist in engineering highly organized functional materials from organic π-conjugated molecules.

show abstract

Section: Photoseponse Sensing and Mechanical Propertiessupporting

confidence: 78%

A Systematic Approach toward Designing Functional Ionic Porphyrin Crystalline Materials

Mazur

Hipps

2018

J. Phys. Chem. C

View full text Add to dashboard Cite

show abstract

“…So, at the time of the RD evaluation, some of these photocarriers were probably still present there (see Figure S4). A similar effect has already been observed for amorphous VOPC and named as persistent photoconductivity (PPC) . If we waited a longer time before the evaluation of the photoregeneration (30 min, not 30 s as defined in the methodology), we obtained small positive values of the RD, mostly close to 0% (Figure S4).…”

Section: Results and Discussionsupporting

confidence: 76%

“…A similar effect has already been observed for amorphous VOPC and named as persistent photoconductivity (PPC). 41 If we waited a longer time before the evaluation of the photoregeneration (30 min, not 30 s as defined in the methodology), we obtained small positive values of the RD, mostly close to 0% (Figure S4). The inefficiency of the photoregeneration in the case of H 2 Pc forced us to apply thermal regeneration by temporal increases of the operating temperature to 90 °C.…”

Section: ■ Results and Discussionmentioning

confidence: 97%

Phthalocyanine Photoregeneration for Low Power Consumption Chemiresistors

et al. 2018

View full text Add to dashboard Cite

It is well-known that the applicability of phthalocyanine chemiresistors suffers from long recovery time after NO 2 exposure. This circumstance enforces the necessity to operate the sensors at elevated temperatures (150−200 °C), which shortens the sensor lifetime and increases its power consumption (regardless, a typical measurement period is longer than 15 min). In this paper, we propose a new method for fast and effective recovery by UV−vis illumination at a low temperature (55 °C). The method is based on short illumination following short NO 2 exposure. To support and optimize the method, we investigated the effects of light in the wavelength and intensity ranges of 375−850 nm and 0.2−0.8 mW/mm 2 , respectively, on the rate of NO 2 desorption from the phthalocyanine sensitive layer during the recovery period. This investigation was carried out for a set of phthalocyanine materials (ZnPc, CuPc, H 2 Pc, PbPc, and FePc) operating at slightly elevated temperatures (55−100 °C) and was further supported by the analysis of UV−vis and FTIR spectral changes. We found out that the light with the wavelength shorter than 550 nm significantly accelerates the NO 2 desorption from ZnPc, CuPc, and FePc, and allows bringing the measurement period under 2 min and decreasing the sensor power consumption by 75%. Possible mechanisms of the light-stimulated desorption are discussed.

show abstract

“…24 In addition, the highly conjugated electronic structure with 18 p electrons combined to properties such as electroactivity, semiconductivity, photoconductivity, photochemical activity, electrochromism, luminescence, non-linear optics, and optical storage lead to great potentiality for diverse applications. [25][26][27][28][29][30][31][32] Particularly important is the possibility of forming thin films of phthalocyanines through different techniques such as LbL, 16,19 physical vapor deposition (PVD) either by thermal evaporation 33,34 or sputtering, 35 Langmuir-Blodgett (LB), 36,37 electrodeposition, 38 spin-coating, 39 and casting, 40 since many organic devices use the element transducers in the form of thin films. For instance, promising technological applications have been suggested for phthalocyanines in the form of thin films for light emitting diodes, 41 transistors, 42 solar cells, 19 liquid crystals, 43 fuel cells, 44 and sensors.…”

Section: Introductionmentioning

confidence: 99%

Iron phthalocyanine in non-aqueous medium forming layer-by-layer films: growth mechanism, molecular architecture and applications

Aléssio

Rodrı́guez-Méndez

Sáez

et al. 2010

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The application of organic thin films as transducer elements in electronic devices has been widely exploited, with the electrostatic layer-by-layer (LbL) technique being one of the most powerful tools to produce such films. The conventional LbL method, however, is restricted in many cases to water soluble compounds. Here, an alternative way to produce LbL films containing iron phthalocyanine (FePc) in non-aqueous media (chloroform) is presented. This film fabrication was made possible by exploiting the specific interactions between Fe and NH(2) groups from PAH, poly(allylamine hydrochloride) used as the supporting layer, leading to the formation of bilayers structured as (PAH/FePc)(n). We have also incorporated silver nanoparticles (AgNPs) in LbL films with (PAH/FePc/AgNP)(n) trilayers, making it possible to achieve the surface-enhanced Raman scattering (SERS) phenomenon. The molecular architecture of the LbL films was determined through different techniques. The growth was monitored with UV-Vis absorption spectroscopy, their morphology characterized by optical and scanning electron (SEM) microscopes, and their molecular organization determined using FTIR. The electrochemical properties of the LbL films were successfully applied in detecting dopamine in KCl aqueous solutions at different concentrations using cyclic voltammetry. The results confirmed that the LbL films from FePc in non-aqueous media keep their electroactivity, while showing an interesting electrocatalytic effect. The SERS phenomenon suggested that FePc aggregates might be directly involved in the maintenance of the electroactivity of the LbL films.

show abstract

Observation of persistent photoconductivity in vanadyl phthalocyanine

Cited by 18 publications

References 26 publications

A Systematic Approach toward Designing Functional Ionic Porphyrin Crystalline Materials

A Systematic Approach toward Designing Functional Ionic Porphyrin Crystalline Materials

Phthalocyanine Photoregeneration for Low Power Consumption Chemiresistors

Iron phthalocyanine in non-aqueous medium forming layer-by-layer films: growth mechanism, molecular architecture and applications

Contact Info

Product

Resources

About