Panagiotis A. Argitis - Academia.edu (original) (raw)

Papers by Panagiotis A. Argitis

Physical Chemistry Chemical Physics, 2018

The thermally-induced multi-electron reduction of [P2Mo18O62]6−anions onto dielectric substrate (... more The thermally-induced multi-electron reduction of [P2Mo18O62]6−anions onto dielectric substrate (SiO2) under ambient conditions is attributed to the oxidation of ammonium counterions.

Organic Electronics, May 1, 2012

ABSTRACT In this work we demonstrate the unique hole injection and transport properties of a subs... more ABSTRACT In this work we demonstrate the unique hole injection and transport properties of a substoichiometric tungsten oxide with precise stoichiometry, in particular WO2.5, obtained after the controlled hydrogen reduction during growth of tungsten oxide, using a simple hot-wire vapor deposition technique. We present clear evidence that tungsten suboxide exhibits metallic character and that an almost zero hole injection barrier exists at the anode/polymer interface due to the formation/occupation of electronic gap states near the Fermi level after oxide’s reduction. These states greatly facilitate hole injection and charge generation/electron extraction enabling the demonstration of extremely efficient hole only devices. WO2.5 films exhibit metallic-like conductivity and, thus, can also enhance charge transport at both anode and cathode interfaces. Electroluminescent devices using WO2.5 as both, hole and electron injection layer, and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1′,3}-thiadiazole)] (F8BT) as the emissive layer exhibited high efficiencies up to 7 cd/A and 4.5 lm/W, while, stability studies revealed that these devices were extremely stable, since they were operating without encapsulation in air for more than 700 h.

Social Science Research Network, 2022

Proceedings of SPIE, Mar 22, 2016

In this work, direct-write, high-resolution multiphoton photolithography using doped random metha... more In this work, direct-write, high-resolution multiphoton photolithography using doped random methacrylic co-polymer thin films is demonstrated, using a continuous wave ultraviolet (UV) 375 nm diode laser source. The random copolymers are specifically designed for enhancing resolution and addressing issues arising from laser ablation processes, such as the berm-formation around the created holes in the film, which can be accessed by tuning the polymeric material properties including Tg, surface adhesion etc. The methacrylic copolymer is composed of monomers, each of them especially selected to improve individual properties. The material formulations comprise perylene molecules absorbing at the exposure wavelength where the polymeric matrix is transparent. It was found that if the radiation intensity exceeds a certain threshold, the perylene molecules transfer the absorbed light energy to the acrylate polymer matrix leading to polymer degradation and ablation of the exposed areas. The non-linear nature of the light absorption and energy transfer processes resulted in the creation of holes with critical dimensions well below the used wavelength reaching the sub 50 nm domain. Arrays of holes having various dimensions were fabricated in the laser ablation experiments using a directwrite laser system developed specifically for the purposes of this project.

Sustainable Energy and Fuels, 2022

The presence of defects formed during the growth and crystallization of perovskite films is a lim... more The presence of defects formed during the growth and crystallization of perovskite films is a limiting factor to achieve high efficiency and stability in perovskite solar cells.

Nano Energy, Apr 1, 2017

Polymer solar cells have undergone rapid development in recent years. Their limited stability to ... more Polymer solar cells have undergone rapid development in recent years. Their limited stability to environmental influence and during illumination, however, still remains a major stumbling block to the commercial application of this technology. Several attempts have been made to address the instability issue, mostly concentrated on the insertion of charge transport interlayers in the device stack. Although zinc oxide (ZnO) is one of the most common electron transport materials in those cells, the presence of defects at the surface and grain boundaries significantly affects the efficiency and stability of the working devices. To address these issues, we herein employ hydrogen-doping of the ZnO electron extraction material. It is found that devices based on photoactive layers composed of blends of poly(3-hexylthiophene) (P3HT) with electron acceptors possessing different energy levels, such as [6,6]-phenyl-C70butyric acid methyl ester (PC70BM) or indene-C60 bisadduct (IC60BA) enhanced the photovoltaic performance considerably when using the hydrogen-doped ZnO. In particular, it is observed that the maximum power conversion efficiency (PCE) reaches values of 4.62% and 6.65%, respectively, which are much higher than those of the cells with the pristine ZnO (3.08% and 4.51%). Most significantly, the degradation of non-encapsulated solar cells when exposed to ambient or under prolonged illumination is studied and it is found that devices based on un-doped ZnO showed poor environmental stability and significant photo-degradation while those using hydrogen-doped ZnO interlayers exhibited high long-term ambient stability and maintained nearly 80-90% of their initial PCE values after 40 hours of 1.5 AM illumination. All mechanisms responsible for this enhanced device stability are elucidated and corresponding models are proposed. This work successfully addresses and tackles the device instability problem of polymer solar cells and the key findings pave the way for the upscaling of these and, perhaps, of related devices such as perovskite solar cells.

Two gallium porphyrins, a tetraphenyl GaCl porphyrin, termed as (TPP)GaCl, and an octaethylporphy... more Two gallium porphyrins, a tetraphenyl GaCl porphyrin, termed as (TPP)GaCl, and an octaethylporphyrin GaCl porphyrin, termed as (OEP)GaCl were synthesized to use as electron cascade in ternary organic bulk heterojunction films. A perfect matching of both gallium porphyrins energy levels with that of poly(3-hexylthiophene-2,5-diyl) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) polymer donor and the 6,6-phenyl C71 butyric acid methyl ester (PCBM) fullerene acceptor forming an efficient cascade system that could facilitate electron transfer between donor and acceptor was demonstrated. Therefore, ternary organic solar cells (OSCs) using the two porphyrins in various concentration were fabricated, where a performance enhancement was obtained. In particular, (TPP)GaCl-based ternary OSCs of low concentration (1:0.05 vv%) exhibited a ~17 % increase of the power conversion efficiency (PCE) compared with the binary device due to improved exciton dissociation, electron transport and reduced recombination. On the other hand, ternary OSCs with the (TPP)GaCl of high concentration (1:0.1 vv%) and (OEP)GaCl (1:0.05 and 1:0.1 vv%) showed poorest efficiencies due to very rough nanomorphology and suppressed crystallinity of ternary films when the GaCl porphyrin introduced in the blend, as revealed from X-ray diffraction (XRD) and atomic force microscopy (AFM). The best performed devices exhibited also improved photostability, when exposed to sunlight illumination for a period of 8 h than the binary OSCs, attributed to the suppressed photodegradation of the ternary (TPP)GaCl 1:0.05-based photoactive film.

Research Square (Research Square), Mar 10, 2021

The development of all-printed, exible solar cells of high e ciency and ultra-low weight will off... more The development of all-printed, exible solar cells of high e ciency and ultra-low weight will offer advancements for new market entrants. Herein, we report the design and fabrication of all-printed in ambient air, super-exible perovskite solar cells with approaching 20% power conversion e ciency and extremely low weight of 5.1 g m-2 leading to an unprecedented power-to-weight ratio of 38,470 W Kg-1. This performance advance was achieved through the design of a highly transparent and conducting nanopaper used as a free-standing bottom electrode (FSBE). The FSBE consisted of cellulose nanocrystals grafted with semi-metallic super-reduced polyoxometalate clusters that enabled high conductivities up to 18 S cm-1 combined with transparency >96%. It also acted as a conformal barrier preventing performance loss upon heating at 95 oC under continuous illumination in inert environment; and strong resistance to decomposition when immersed in a mild citric acid water solution for 100 days, which we further exploit to demonstrate full device recyclability. The inherent exibility of cellulose nanocrystals enabled remarkable exibility of these cells under 2,000 repeated bending and folding cycles and mechanical strength upon extensive strain up to 20%. Notably, the nanopaper remained unaffected for strains up to 60%. These ndings open the door for e cient and lightweight solar cells with a low environmental impact. Main Text Thin and lightweight solar cells of high speci c power that are exible and elastic under tensile strain are appealing for emerging applications in aerospace, unmanned aerial vehicles and integration in automobiles, buildings, textiles and moving parts of machinery 1. Key elements that will enable the exible solar cell technology to further evolve are the development of low-cost and abundant materials for the device substrate, electrodes and functional layers combined with the capability to be printed using highyield low-cost methods. Promising candidates are the emerging photovoltaic technologies based-on solution-processed semiconductors, such as organics 2 , colloidal quantum dots 3 and organic-inorganic halide perovskites 4. Particularly, perovskite solar cells (PSCs) have already reached commercially viable power conversion e ciencies (PCEs) up to 25.2% 5-8 for rigid devices fabricated on glass substrates and up to 20.7% for exible ones fabricated on plastics 9-13. This progress was realized by tailoring the composition and dimensionality of the perovskite absorber, advancements related to low-temperature deposition methods to improve the perovskite layer's properties, and interface materials to improve the energy level alignment 14-20. However, the majority of the existing solar cells, including perovskite ones, are fabricated either on glass or on plastic substrates coated with indium tin oxide (ITO) or uorinated tin oxide. These substrates increase the device thickness and weight (especially glass) and are unsuitable when considering fully solution printing capability of solar cells 21-23. More importantly, the conductive ITO layer (a commonly utilized electrode material for a vast variety of optoelectronic devices), is both expensive and mechanically fragile. Low-cost, Earth-abundant, and easily recyclable materials for substrates and

Proceedings of SPIE, Mar 21, 2016

The main target of the current work was to develop new polymeric materials for lithographic appli... more The main target of the current work was to develop new polymeric materials for lithographic applications, the main chain of which is cleaved under the influence of photogenerated acid. Acetals have been chosen as functional groups in the main polymer chain since they can be cleaved in the presence of an acid while they remain untouched in alkaline ambient. The synthesized polymers were designed to bear in addition suitable functional groups for the achievement of desirable lithographic characteristics (thermal stability, acceptable glass transition temperature, etch resistance, proper dissolution behaviour). The synthesis was carried out via polyaddition of a vinyloxyl compound and a diol compound to produce novel polymers with acetal repeating units in their backbone. We chose polyaromatic hydrocarbons as diol units to achieve increased etch resistance. In addition, the polyaromatic units allow exposure at 193 nm as well, where the absorption of simple aromatics is prohibitively high. Good solubility and increased surface adhesion were achieved by choosing cycloaliphatic vinyloxyl ethers as the second component for the polyaddition. In addition, the same route can be followed to incorporate chromophores that can tune the resist absorbance in different spectral regions. Furthermore, single component systems can be designed following this approach by the incorporation of suitable PAGs in the main chain.

In this work, the effect of microwave annealing of tungsten oxide films, which are widely used to... more In this work, the effect of microwave annealing of tungsten oxide films, which are widely used to enhance hole extraction in organic optoelectronic devices such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs), on the nanomorhology and optical properties of bulk heterojuction (BHJ) OPVs, is demonstrated. It is found that a short microwave exposure of under-stoichiometric oxide film enhances the crystallinity/ordering of poly(3-hexylthiophene):[6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) blends when coated on microwave annealed tungsten oxide films, as revealed from X-ray diffraction and UV-Vis absorption measurements. The performance of OPVs using microwave annealed tungsten oxides and based on a P3HT:PC71BM blend as the photoactive layer reached values of 3.97%, an increase of about 53% compared with the device using the under-stoichiometric tungsten oxide hole extraction layer not subjected to microwave annealing.

The aim of the current work was to develop new sensitive polymeric materials for lithographic app... more The aim of the current work was to develop new sensitive polymeric materials for lithographic applications, focusing in particular to EUV lithography, where the main polymer chain is cleaved under the influence of photogenerated acid. Resist materials based on the cleavage of polymer main chain are in principle capable to create very small structures, to the dimensions of the monomers that they consist of. Nevertheless, in the case of the commonly used non-chemically amplified materials of this type issues like sensitivity and poor etch resistance limit their areas of application, whereas inadequate etch resistance and unsatisfactory process reliability are the usual problems encountered in acid catalyzed materials based on main chain scission. In our material design, the acid catalyzed chain cleavable polymers contain very sensitive moieties in their backbone while they remain intact in alkaline ambient. These newly synthesized polymers bear in addition suitable functional groups for the achievement of desirable lithographic characteristics (thermal stability, acceptable glass transition temperature, etch resistance, proper dissolution behavior, adhesion to the substrate). Our approach for achieving acceptable etch resistance, a main drawback in other main chain cleavable resists, is based on the introduction of polyaromatic hydrocarbons in the polymeric backbone, whereas the incorporation of an inorganic component further enhances the etch resistance. Single component systems can also be designed following the proposed approach by the incorporation of suitable PAGs and base quencher molecules in the main chain. Resist formulations based on a random copolymer designed according to the described rules evaluated in EUV exhibit ultrahigh sensitivity, capability for high-resolution patterning and overall processing characteristics that make them strong candidates upon further optimization.

Advanced Materials Interfaces, Jun 24, 2022

Journal of Physical Chemistry C, Sep 8, 2016

A method is developed for extracting the direct current conductivity (σdc) of ion-conducting mate... more A method is developed for extracting the direct current conductivity (σdc) of ion-conducting materials from frequency- and time-domain dielectric spectroscopy measurements. This method exploits the electrode polarization effects arising from the charging of an ion-blocking capacitor and provides a useful way of obtaining σdc for ionic conductors that do not exhibit a frequency- (time-) independent conductivity plateau; the latter absence of plateau is often encountered in the case of thin-film materials. It allows, by proper design of the test cells, the estimation of σdc independently of the specimen thickness, as demonstrated herein for SiO2 blocking layers and electrolyte systems made of a polyoxometalate (POM) molecule embedded in poly(methyl methacrylate) (PMMA) polymeric matrices. For different postpreparation and measurement conditions, the σdc values obtained for thick (8 μm) POM–PMMA layers are in good agreement not only with the observed conductivity plateaus but also with the values determined ...

Advanced Energy Materials, Jun 3, 2020

materials design and synthesis and to ingenious device and interfacial engineering. Such impressi... more materials design and synthesis and to ingenious device and interfacial engineering. Such impressive performance was enabled by two terminal monolithically integrated organic/organic and perovskite/silicon tandem architectures, respectively. [1,2] Further advances toward commercialization require increased cell stabilities, an area where significant efforts have been devoted recently. As interfaces have been shown to play a critical role in optimizing both cell efficiency and stability, interface engineering has proven to be a key method with many significant successes but with some critical issues remaining still unresolved. [5-8] Two interfacial engineering strategies have been mainly employed: chemical modification or treatment of the organic or the perovskite active layer with various materials to passivate surface and bulk defects and modulate the interface energetics [9-11] or incorporation of a suitable interfacial layer. The latter should possess multiple functionalities such as alleviating interfacial recombination losses, assisting carrier transport and extraction and enhancing charge collection efficiency. [12] Interfacial materials such as inorganic transition metal oxides (TiO 2 , ZnO, MoO x , WO x , NiO x , V 2 O 5 , SnO 2 , Al 2 O 3 , ZrO 2 , etc.) either in their pristine state or upon doping, [13-34] molecular oxides such as polyoxometalates, [35,36] fluorides, [37] organic molecules and conductive polymers, [38-43] self-assembled monolayers (SAMs) and ionic

Chemistry of Materials, Jun 1, 2004

In this paper we describe the lithographic behavior and related material properties of a new clas... more In this paper we describe the lithographic behavior and related material properties of a new class of chemically amplified, positive tone, silicon-containing methacrylate photoresists incorporating the polyhedral oligomeric silsesquioxane (POSS) group as the etch-resistant component. POSS-bearing monomers were copolymerized with methacrylic acid (MA), tertbutyl methacrylate (TBMA), tert-butyl trifluoro methacrylate (TBTFMA), itaconic anhydride (IA), and 2-(trifluoromethyl) acrylic acid (TFMA), in various compositions. A perfluorooctylsulfonate-based photoacid generator (PAG) was used to deprotect TBMA (or TBTFMA) to base soluble carboxylic acid by heating after exposure. XPS and angular XPS analysis were used to examine possible surface segregation phenomena. It was proven that POSS surface enrichment occurs for the POSS-TBMA copolymers while surface segregation may be reduced if suitable additional resist components are selected. The POSS-based resists were studied for 157-nm lithographic applications and found to have high sensitivity (<10 mJ/cm 2 under open field exposure), no silicon outgassing, and sub-100-nm resolution capabilities. Ninety nanometer patterns in 100-nm thick films were resolved. At present, their absorbance is high (∼4 µm-1) for single-layer lithographic applications at 157 nm; however, high etch resistance in oxygen plasma makes them suitable for bilayer schemes.

Chemical Society Reviews, 2020

Here we review the recent strategies for developing organic and inorganic molecular materials for... more Here we review the recent strategies for developing organic and inorganic molecular materials for application as electron and hole transport layers and as additives to achieve high efficiency and stability perovskite solar cells.

Here we report on organic light-emitting diodes incorporating two porphyrin compounds exhibiting ... more Here we report on organic light-emitting diodes incorporating two porphyrin compounds exhibiting red to near infra-red (IR) emission. Especially, the compound with the long side groups (porphyrin II) has a red-shifted emission (λPLmax = 793 nm) compared to the compound with the single porphyrin ring (porphyrin I, (λPLmax = 723 nm) as a consequence of its extended π-conjugation. We studied the electroluminescence of blends with poly(9-vinyl carbazole) (PVK), achieving high color purity near-infrared electroluminescence.

ΟΡΙΣΜΕΝΑ 2:18 ΚΑΙ 1:12 ΕΤΕΡΟΠΟΛΥΟΝΙΟΝΤΑ ΦΩΤΟΑΝΑΓΟΝΤΑΙ ΟΤΑΝ ΦΩΤΙΣΘΟΥΝ ΜΕ ΦΩΣ ΤΗΣΠΕΡΙΟΧΗΣ ΤΟΥ ΥΠΕΡΙ... more ΟΡΙΣΜΕΝΑ 2:18 ΚΑΙ 1:12 ΕΤΕΡΟΠΟΛΥΟΝΙΟΝΤΑ ΦΩΤΟΑΝΑΓΟΝΤΑΙ ΟΤΑΝ ΦΩΤΙΣΘΟΥΝ ΜΕ ΦΩΣ ΤΗΣΠΕΡΙΟΧΗΣ ΤΟΥ ΥΠΕΡΙΩΔΟΥΣ ΚΑΙ ΚΟΝΤΙΝΟΥ ΟΡΑΤΟΥ ΠΑΡΟΥΣΙΑ ΠΟΙΚΙΛΙΑΣ ΟΡΓΑΝΙΚΩΝ ΟΥΣΙΩΝ. ΣΤΗΝ ΠΕΡΙΠΤΩΣΗ ΤΟΥ P2W180626 - Η ΦΩΤΟΑΝΑΓΩΓΗ ΠΡΟΧΩΡΕΙ ΚΑΤΑ ΣΤΑΔΙΑ ΚΑΙ ΟΔΗΓΕΙΣΤΟ ΣΧΗΜΑΤΙΣΜΟ ΠΡΟΙΟΝΤΩΝ ΙΚΑΝΩΝ, ΑΠΟ ΘΕΡΜΟΔΥΝΑΜΙΚΗ ΑΠΟΨΗ, ΝΑ ΠΡΟΚΑΛΕΣΟΥΝ ΑΝΑΓΩΓΗ ΤΟΥ Η2Ο ΠΑΡΑΓΟΝΤΑΣ Η2. ΠΑΡΑΓΩΓΗ Η2 ΠΡΑΓΜΑΤΙ ΛΑΜΒΑΝΕΙ ΧΩΡΑ ΤΟΣΟ ΠΑΡΟΥΣΙΑ ΟΣΟ ΚΑΙ ΑΠΟΥΣΙΑ ΚΑΤΑΛΥΤΗ ΡΤ. ΟΙ ΣΤΑΘΕΡΕΣ ΤΑΧΥΤΗΤΑΣ ΓΙΑ ΤΗΝ ΠΑΡΑΓΩΓΗ ΑΥΤΗ ΗΤΑΝ ΣΥΝΑΡΤΗΣΗ ΤΟΥ ΑΝΑΓΩΓΙΚΟΥ ΣΤΑΔΙΟΥ, ΤΟΥ ΡΗ ΚΑΙ ΤΗΣ ΠΑΡΟΥΣΙΑΣ ΚΑΤΑΛΥΤΗ ΡΤ ΚΑΙ ΗΤΑΝ ΤΗΣ ΤΑΞΗΣ ΤΟΥ 10-4 5-1. ΑΝΤΙΚΑΤΑΣΤΑΣΗ ΑΤΟΜΩΝ ΜΟ 'Η W ΑΠΟ ΑΤΟΜΑ V ΣΕ 1:12 ΕΤΕΡΟΠΟΛΥΑΝΙΟΝΤΑ ΜΕΤΑΤΟΠΙΖΕΙ ΤΟ ΦΑΣΜΑ ΑΠΟΡΡΟΦΗΣΗΣ ΤΟΥΣ ΠΡΟΣ ΤΟ ΟΡΑΤΟ ΚΑΘΙΣΤΩΝΤΑΣ ΔΥΝΑΤΗ ΤΗΝ ΦΩΤΟΑΝΑΓΩΓΗ ΤΟΥΣ ΜΕ ΠΑΡΑΛΛΗΛΗ ΟΞΕΙΔΩΣΗ ΟΡΓΑΝΙΚΩΝ ΕΝΩΣΕΩΝ ΜΕ ΦΩΣ ΤΗΣ ΠΕΡΙΟΧΗΣΑΥΤΗΣ. Η ΦΩΤΟΑΝΑΓΩΓΗ ΑΥΤΗ ΟΜΩΣ ΠΡΟΧΩΡΕΙ ΜΕ ΜΙΚΡΟΤΕΡΗ ΚΒΑΝΤΙΚΗ ΑΠΟΔΟΣΗ ΚΑΤΑ ΤΟΝΦΩΤΙΣΜΟ ΣΤΙΣ ΤΑΙΝΙΕΣ Ο -> V (Λ > 400ΝΜ) ΣΕ ΣΥΓΚΡΙΣΗ ΜΕ ΤΙΣ ΑΝΤΙΣΤΟΙΧΕΣ ΤΑΙΝΙΕΣΟ -> W ΚΑΙ O -> MO. ΕΠΙΣΗΣ ΜΕ ΦΩΣ Λ > 400ΝΜ ΔΕΝ ΠΡΟΣΤΙΘΕΝΤΑΙ ΠΕΡΙΣΣΟΤΕΡΑ ΑΠΟ 2ΗΛΕΚΤΡΟΝΙΑ ΣΤΑ ΔΥΟ ΜΙΚΤΑ ΕΤΕΡΟΠΟΛΥΑΝΙΟΝΤΑ ΚΑΙ ΔΕΝ ΠΑΡΑΓΕΤΑΙ Η2.

Springer eBooks, 1986

Heteropoly electrolytes (HPC) of molybdenum and tungsten are photosensitive in near visible and u... more Heteropoly electrolytes (HPC) of molybdenum and tungsten are photosensitive in near visible and ultra violet light in presence of a great variety of organic compounds. Photoexcitation results in “reversible” stepwise reduction of HPC with concomitant oxidation of organic compounds. Photoreduction proceeds to the extent that the rate of photo- reduction is matched by the back reoxidation by H+ or oxygen. At:his stage a steady state is obtained at which H2 is produced with a quantum yield of 1%, whereas, maximum quantum yield for alcohol oxidation in presence of oxygen is 10–15%. Coupling the photoreduced and oxidized species into a photogalvanic (photofuel) cell a current is produced with an efficiency of 1–2 electron per 100 photons. Incorporation of vanadium into HPC shifts the absorption toward the visible, but there seems to be no improvement in photochemistry.