Polymers

Research

17 pages, 4915 KiB

Open AccessArticle

Synthesis and Impedance Spectroscopy of Poly(p-phenylenediamine)/Montmorillonite Composites

by Udit Acharya, Patrycja Bober, Muhammed Arshad Thottappali, Zuzana Morávková, Magdalena Konefał and Jiří Pfleger

Polymers 2021, 13(18), 3132; https://doi.org/10.3390/polym13183132 - 16 Sep 2021

Cited by 7 | Viewed by 3241

Abstract

Poly(p-phenylenediamine)/montmorillonite (PPDA/MMT) composites were prepared by the oxidative polymerization of monomers intercalated within the MMT gallery, using ammonium peroxydisulfate as an oxidant. The intercalation process was evidenced by X-ray powder diffraction. The FT-IR and Raman spectroscopies revealed that, depending on the [...] Read more.

Poly(p-phenylenediamine)/montmorillonite (PPDA/MMT) composites were prepared by the oxidative polymerization of monomers intercalated within the MMT gallery, using ammonium peroxydisulfate as an oxidant. The intercalation process was evidenced by X-ray powder diffraction. The FT-IR and Raman spectroscopies revealed that, depending on the initial ratio between monomers and MMT in the polymerization mixture, the polymer or mainly oligomers are created during polymerization. The DC conductivity of composites was found to be higher than the conductivity of pristine polymer, reaching the highest value of 10⁻⁶ S cm⁻¹ for the optimal MMT amount used during polymerization. Impedance spectroscopy was performed over wide frequency and temperature ranges to study the charge transport mechanism. The data analyzed in the framework of conductivity formalism suggest different conduction mechanisms for high and low temperature regions. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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13 pages, 3573 KiB

Open AccessArticle

Three Destinies of Solution-Processable Polymer Light-Emitting Diodes under Long-Time Operation

by Ruslana Udovytska, Pavel Chulkin, Aleksandra Wypych-Puszkarz and Jaroslaw Jung

Polymers 2021, 13(11), 1853; https://doi.org/10.3390/polym13111853 - 2 Jun 2021

Cited by 4 | Viewed by 2385

Abstract

The article describes three different ways of polymer light-emitting diode (PLED) degradation, caused by damage of the protective layer. The electroluminescence and charge-transport properties of a completely encapsulated diode, the diodes with a leaky protective layer and diodes without encapsulation were compared under [...] Read more.

The article describes three different ways of polymer light-emitting diode (PLED) degradation, caused by damage of the protective layer. The electroluminescence and charge-transport properties of a completely encapsulated diode, the diodes with a leaky protective layer and diodes without encapsulation were compared under long-time exploitation. The studied devices incorporated Super Yellow light-emitting poly-(1,4-phenylenevinylene) PPV copolymer as an electroluminescence component, and (poly-(3,4-ethylenedioxythiophene)–poly-(styrene sulfonate) (PEDOT:PSS) as a charge-transport layer between the indium tin oxide (ITO) anode and aluminum–calcium cathode. To analyze the PLED degradation mechanism regarding charge transport, impedance spectroscopy was used. The values of resistance and capacitance of the internal layers revealed an effect of applied voltage on charge carrier injection and recombination. The factors responsible for the device degradation were analyzed on a macromolecular level by comparing the plots of voltage dependence of resistance and capacitance at different operation times elapsed. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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14 pages, 3293 KiB

Open AccessArticle

The Quinonoid Zwitterion Interlayer for the Improvement of Charge Carrier Mobility in Organic Field-Effect Transistors

by Adam Luczak, Angélina Torres Ruiz, Simon Pascal, Adrian Adamski, Jarosław Jung, Beata Luszczynska and Olivier Siri

Polymers 2021, 13(10), 1567; https://doi.org/10.3390/polym13101567 - 13 May 2021

Cited by 5 | Viewed by 2418

Abstract

The interface between the semiconductor and the dielectric layer plays a crucial role in organic field-effect transistors (OFETs) because it is at the interface that charge carriers are accumulated and transported. In this study, four zwitterionic benzoquinonemonoimine dyes featuring alkyl and aryl N [...] Read more.

The interface between the semiconductor and the dielectric layer plays a crucial role in organic field-effect transistors (OFETs) because it is at the interface that charge carriers are accumulated and transported. In this study, four zwitterionic benzoquinonemonoimine dyes featuring alkyl and aryl N-substituents were used to cover the dielectric layers in OFET structures. The best interlayer material, containing aliphatic side groups, increased charge carrier mobility in the measured systems. This improvement can be explained by the reduction in the number of the charge carrier trapping sites at the dielectric active layer interface from 10¹⁴ eV⁻¹ cm⁻² to 2 × 10¹³ eV⁻¹ cm⁻². The density of the traps was one order of magnitude lower compared to the unmodified transistors. This resulted in an increase in charge carrier mobility in the tested poly [2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (DPPDTT)-based transistors to 5.4 × 10⁻¹ cm² V⁻¹ s⁻¹. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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14 pages, 3285 KiB

Open AccessArticle

Charge Carrier Mobility Improvement in Diketopyrrolopyrrole Block-Copolymers by Shear Coating

by Kristina Ditte, Nataliya Kiriy, Jonathan Perez, Mike Hambsch, Stefan C. B. Mannsfeld, Yulia Krupskaya, Ramesh Maragani, Brigitte Voit and Franziska Lissel

Polymers 2021, 13(9), 1435; https://doi.org/10.3390/polym13091435 - 29 Apr 2021

Cited by 7 | Viewed by 3941

Abstract

Shear coating is a promising deposition method for upscaling device fabrication and enabling high throughput, and is furthermore suitable for translating to roll-to-roll processing. Although common polymer semiconductors (PSCs) are solution processible, they are still prone to mechanical failure upon stretching, limiting applications [...] Read more.

Shear coating is a promising deposition method for upscaling device fabrication and enabling high throughput, and is furthermore suitable for translating to roll-to-roll processing. Although common polymer semiconductors (PSCs) are solution processible, they are still prone to mechanical failure upon stretching, limiting applications in e.g., electronic skin and health monitoring. Progress made towards mechanically compliant PSCs, e.g., the incorporation of soft segments into the polymer backbone, could not only allow such applications, but also benefit advanced fabrication methods, like roll-to-roll printing on flexible substrates, to produce the targeted devices. Tri-block copolymers (TBCs), consisting of an inner rigid semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) block flanked by two soft elastomeric poly(dimethylsiloxane) (PDMS) chains, maintain good charge transport properties, while being mechanically soft and flexible. Potentially aiming at the fabrication of TBC-based wearable electronics by means of cost-efficient and scalable deposition methods (e.g., blade-coating), a tolerance of the electrical performance of the TBCs to the shear speed was investigated. Herein, we demonstrate that such TBCs can be deposited at high shear speeds (film formation up to a speed of 10 mm s⁻¹). While such high speeds result in increased film thickness, no degradation of the electrical performance was observed, as was frequently reported for polymer−based OFETs. Instead, high shear speeds even led to a small improvement in the electrical performance: mobility increased from 0.06 cm² V⁻¹ s⁻¹ at 0.5 mm s⁻¹ to 0.16 cm² V⁻¹ s⁻¹ at 7 mm s⁻¹ for the TBC with 24 wt% PDMS, and for the TBC containing 37 wt% PDMS from 0.05 cm² V⁻¹ s⁻¹ at 0.5 mm s⁻¹ to 0.13 cm² V⁻¹ s⁻¹ at 7 mm s⁻¹. Interestingly, the improvement of mobility is not accompanied by any significant changes in morphology. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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19 pages, 5515 KiB

Open AccessArticle

Effect of TADF Assistance on Performance Enhancement in Solution Processed Green Phosphorescent OLEDs

by Ewelina Witkowska, Gabriela Wiosna-Salyga, Ireneusz Glowacki, Tung-Huei Ke, Pawel Malinowski and Paul Heremans

Polymers 2021, 13(7), 1148; https://doi.org/10.3390/polym13071148 - 2 Apr 2021

Cited by 4 | Viewed by 3335

Abstract

Many methods have been proposed to increase the efficiency of organic electroluminescent materials applied as an emissive layer in organic light emitting diodes (OLEDs). Herein, we demonstrate enhancement of electroluminescence efficiency and operational stability solution processed OLEDs by employing thermally activated delayed fluorescence [...] Read more.

Many methods have been proposed to increase the efficiency of organic electroluminescent materials applied as an emissive layer in organic light emitting diodes (OLEDs). Herein, we demonstrate enhancement of electroluminescence efficiency and operational stability solution processed OLEDs by employing thermally activated delayed fluorescence (TADF) molecules as assistant dopants in host-guest systems. The TADF assistant dopant (SpiroAC–TRZ) is used to facilitate efficient energy transfer from host material poly(N–vinylcarbazole) (PVK) to a phosphorescent Ir(III) emitter. We present the analysis of energy transfer and charge trapping—two main processes playing a crucial role in light generation in host–guest structure OLEDs. The investigation of photo-, electro- and thermoluminescence for the double-dopant layer revealed that assistant dopant does not only harvest and transfer the electrically generated excitons to phosphorescent emitter molecules but also creates exciplexes. The triplet states of formed PVK:SpiroAC–TRZ exciplexes are involved in the transport process of charge carriers and promote long–range exciton energy transfer to the emitter, improving the efficiency of electroluminescence in a single emissive layer OLED, resulting in devices with luminance exceeding 18 000 cd/m² with a luminous efficiency of 23 cd/A and external quantum efficiency (EQE) of 7.4%. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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14 pages, 14795 KiB

Open AccessArticle

Effects of Counter Anions on AC and DC Electrical Conductivity in Poly(Dimethylsiloxane) Crosslinked by Metal-Ligand Coordination

by Angelika Wrzesińska, Aleksandra Wypych-Puszkarz, Izabela Bobowska and Jacek Ulański

Polymers 2021, 13(6), 956; https://doi.org/10.3390/polym13060956 - 20 Mar 2021

Cited by 4 | Viewed by 2151

Abstract

There is an urgent need for the development of elastic dielectric materials for flexible organic field effect transistors (OFETs). In this work, detailed analysis of the AC and DC electrical conductivity of a series of flexible poly(dimethylsiloxane) (PDMS) polymers crosslinked by metal-ligand coordination [...] Read more.

There is an urgent need for the development of elastic dielectric materials for flexible organic field effect transistors (OFETs). In this work, detailed analysis of the AC and DC electrical conductivity of a series of flexible poly(dimethylsiloxane) (PDMS) polymers crosslinked by metal-ligand coordination in comparison to neat PDMS was performed for the first time by means of broadband dielectric spectroscopy. The ligand was 2,2-bipyridine-4,4-dicarboxylic amide, and Ni²⁺, Mn²⁺, and Zn²⁺ were introduced for Cl⁻, Br⁻, and I⁻ salts. Introduction of metal salt and creation of coordination bonds resulted in higher permittivity values increasing in an order: neat PDMS < Ni²⁺ < Mn²⁺ < Zn²⁺; accompanied by conductivity values of the materials increasing in an order: neat PDMS < Cl⁻ < I⁻ < Br⁻. Conductivity relaxation time plot as a function of temperature, showed Vogel-Fulcher–Tammann dependance for the Br⁻ salts and Arrhenius type for the Cl⁻ and I⁻ salts. Performed study revealed that double-edged challenge can be obtained, i.e., dielectric materials with elevated value of dielectric permittivity without deterioration too much the non-conductive nature of the polymer. This opens up new perspectives for the production of flexible dielectrics suitable for gate insulators in OFETs. Among the synthesized organometallic materials, those with chlorides salts are the most promising for such applications. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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11 pages, 4147 KiB

Open AccessArticle

Influence of the Catalyst Layer Structure Formed by Inkjet Coating Printer on PEFC Performance

by Yushi Tamaki and Kimihiko Sugiura

Polymers 2021, 13(6), 899; https://doi.org/10.3390/polym13060899 - 15 Mar 2021

Cited by 4 | Viewed by 2383

Abstract

In this study, we investigated the influence of the Catalyst-Layer (CL) structure on Polymer Electrolyte Fuel Cell (PEFC) performance using an inkjet coating printer, and we especially focused on the CL thickness and the electrode area. In order to evaluate the influence of [...] Read more.

In this study, we investigated the influence of the Catalyst-Layer (CL) structure on Polymer Electrolyte Fuel Cell (PEFC) performance using an inkjet coating printer, and we especially focused on the CL thickness and the electrode area. In order to evaluate the influence of CL thickness, we prepared four Membrane Electrode Assemblies (MEAs), which have one, four, five and six CLs, respectively, and evaluated it by an overpotential analysis. As a result, the overpotentials of an activation and a diffusion increased with the increase of thickness of CL. From Energy Dispersive X-ray spectroscopy (EDX) analysis, because platinum twines most ionomers and precipitates, the CL separates into a layer of platinum with a big grain aggregate ionomer and the mixing layer of platinum and ionomer during the catalyst ink drying process. Consequently, the activation overpotential increased because the three-phase interface was not able to be formed sufficiently. The gas diffusivity of the multilayer catalyst electrode was worse than that of a single layer MEA. The influence of the electrode area was examined by two MEAs with 1 and 9 cm² of electrode area. As a result, the diffusion overpotential of 9 cm² MEA was worse than 1 cm² MEA. The generated condensate was multiplied and moved to the downstream side, and thereafter it caused the flooding/plugging phenomena. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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11 pages, 2997 KiB

Open AccessArticle

Efficient Inverted Solar Cells Using Benzotriazole-Based Small Molecule and Polymers

by Ja Eun Lee, Yoon Kim, Yang Ho Na, Nam Seob Baek, Jae Woong Jung, Yura Choi, Namchul Cho and Tae-Dong Kim

Polymers 2021, 13(3), 393; https://doi.org/10.3390/polym13030393 - 27 Jan 2021

Cited by 4 | Viewed by 1874

Abstract

We synthesized medium-band-gap donor-acceptor (D-A) -type conjugated polymers (PBTZCZ-L and PBTZCZ-H) consisting of a benzotriazole building block as an acceptor and a carbazole unit as a donor. In comparison with the polymers, a small conjugated molecule (BTZCZ-2) was developed, and its structural, thermal, [...] Read more.

We synthesized medium-band-gap donor-acceptor (D-A) -type conjugated polymers (PBTZCZ-L and PBTZCZ-H) consisting of a benzotriazole building block as an acceptor and a carbazole unit as a donor. In comparison with the polymers, a small conjugated molecule (BTZCZ-2) was developed, and its structural, thermal, optical, and photovoltaic properties were investigated. The power conversion efficiency (PCE) of the BTZCZ-2-based solar cell devices was less than 0.5%, considerably lower than those of polymer-based devices with conventional device structures. However, inverted solar cell devices configured with glass/ITO/ZnO:PEIE/BTZCZ-2:PC₇₁BM/MoO₃/Ag showed a tremendously improved efficiency (PCE: 5.05%, J_sc: 9.95 mA/cm², V_oc: 0.89 V, and FF: 57.0%). We believe that this is attributed to high energy transfer and excellent film morphologies. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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9 pages, 2950 KiB

Open AccessCommunication

Fluorescence Switchable Conjugated Polymer Microdisk Arrays by Cosolvent Vapor Annealing

by Hiroshi Yamagishi, Tokiya Matsui, Yusuke Kitayama, Yusuke Aikyo, Liang Tong, Junpei Kuwabara, Takaki Kanbara, Masakazu Morimoto, Masahiro Irie and Yohei Yamamoto

Polymers 2021, 13(2), 269; https://doi.org/10.3390/polym13020269 - 15 Jan 2021

Cited by 7 | Viewed by 2566

Abstract

Depositing minute light emitters into a regular array is a basic but essential technique in display technology. However, conventional lithographic methodologies involve multistep and energy-consuming processes. Here, we develop a facile method in which organic and polymeric fluorescent dyes spontaneously aggregate to form [...] Read more.

Depositing minute light emitters into a regular array is a basic but essential technique in display technology. However, conventional lithographic methodologies involve multistep and energy-consuming processes. Here, we develop a facile method in which organic and polymeric fluorescent dyes spontaneously aggregate to form a patterned microarray. We find that a thin film of fluorescent π-conjugated polymer transforms into micrometer-sized aggregates when exposed to binary organic vapor at ambient temperature. The arrayed microaggregates can be formed over the whole substrate surface when using a quartz substrate that is prepatterned with regular hydrophilic boxes and hydrophobic grids. The resultant microarray is applicable to optical memories and displays when photoswitchable fluorophores are doped into the polymer matrix. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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16 pages, 3097 KiB

Open AccessArticle

Effect of Metal-Ligand Coordination Complexes on Molecular Dynamics and Structure of Cross-Linked Poly(dimethylosiloxane)

by Angelika Wrzesińska, Izabela Bobowska, Paulina Maczugowska, Joanna Małolepsza, Katarzyna M. Błażewska and Aleksandra Wypych-Puszkarz

Polymers 2020, 12(8), 1680; https://doi.org/10.3390/polym12081680 - 28 Jul 2020

Cited by 6 | Viewed by 2869

Abstract

Poly(dimethylosiloxane) (PDMS) cross-linked by metal-ligand coordination has a potential functionality for electronic devices applications. In this work, the molecular dynamics of bipyridine (bpy)–PDMS-MeCl₂ (Me: Mn²⁺, Fe²⁺, Ni²⁺, and Zn²⁺) are investigated by means of [...] Read more.

Poly(dimethylosiloxane) (PDMS) cross-linked by metal-ligand coordination has a potential functionality for electronic devices applications. In this work, the molecular dynamics of bipyridine (bpy)–PDMS-MeCl₂ (Me: Mn²⁺, Fe²⁺, Ni²⁺, and Zn²⁺) are investigated by means of broadband dielectric spectroscopy and supported by differential scanning calorimetry and density functional theory calculations. The study of molecular motions covered a broad range of temperatures and frequencies and was performed for the first time for metal-ligand cross-linked PDMS. It was found that the incorporation of bpy moieties into PDMS chain prevents its crystallization. The dielectric permittivity of studied organometallic systems was elevated and almost two times higher (ε′ ~4 at 1 MHz) than in neat PDMS. BpyPDMS-MeCl₂ complexes exhibit slightly higher glass transition temperature and fragility as compared to a neat PDMS. Two segmental type relaxations (α and α_ac) were observed in dielectric studies, and their origin was discussed in relation to the molecular structure of investigated complexes. The α_ac relaxation was observed for the first time in amorphous metal-ligand complexes. It originates from the lower mobility of PDMS polymer chains, which are immobilized by metal-ligand coordination centers via bipyridine moieties. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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17 pages, 2978 KiB

Open AccessArticle

Impact of Hydrogen Bonds Limited Dipolar Disorder in High-k Polymer Gate Dielectric on Charge Carrier Transport in OFET

by Bartosz Paruzel, Jiří Pfleger, Jiří Brus, Miroslav Menšík, Francesco Piana and Udit Acharya

Polymers 2020, 12(4), 826; https://doi.org/10.3390/polym12040826 - 5 Apr 2020

Cited by 3 | Viewed by 3140

Abstract

The paper contributes to the characterization and understanding the mutual interactions of the polar polymer gate dielectric and organic semiconductor in organic field effect transistors (OFETs). It has been shown on the example of cyanoethylated polyvinylalcohol (CEPVA), the high-k dielectric containing strong polar [...] Read more.

The paper contributes to the characterization and understanding the mutual interactions of the polar polymer gate dielectric and organic semiconductor in organic field effect transistors (OFETs). It has been shown on the example of cyanoethylated polyvinylalcohol (CEPVA), the high-k dielectric containing strong polar side groups, that the conditions during dielectric layer solidification can significantly affect the charge transport in the semiconductor layer. In contrast to the previous literature we attributed the reduced mobility to the broader distribution of the semiconductor density of states (DOS) due to a significant dipolar disorder in the dielectric layer. The combination of infrared (IR), solid-state nuclear magnetic resonance (NMR) and broadband dielectric (BDS) spectroscopy confirmed the presence of a rigid hydrogen bonds network in the CEPVA polymer. The formation of such network limits the dipolar disorder in the dielectric layer and leads to a significantly narrowed distribution of the density of states (DOS) and, hence, to the higher charge carrier mobility in the OFET active channel made of 6,13-bis(triisopropylsilylethynyl)pentacene. The low temperature drying process of CEPVA dielectric results in the decreased energy disorder of transport states in the adjacent semiconductor layer, which is then similar as in OFETs equipped with the much less polar poly(4-vinylphenol) (PVP). Breaking hydrogen bonds at temperatures around 50 °C results in the gradual disintegration of the stabilizing network and deterioration of the charge transport due to a broader distribution of DOS. Full article

(This article belongs to the Special Issue Printed Organic Electronics—Solution Processable Polymers and Interlayers)

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