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From Macromolecules to Materials for Optoelectronic Devices

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 December 2018) | Viewed by 35046

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Special Issue Editor

Dr. Ana Charas

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Guest Editor

Organic Electronics Group, Instituto de Telecomunicações, Instituto Superior Técnico-Torre Norte, Av. Rovisco Pais,1, 1049-001 Lisboa, Portugal
Interests: organic conductors and semiconductors; electroluminescent materials; organic photovoltaic cells; organic field-effect transistors; self assembly, nanostructuring of organic polymers and small molecules
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The aim of this Special Issue, devoted to the theme "From Macromolecules to Materials for Optoelectronic Devices" is to address current challenges and developments in the field of organic optoelectronics engaging the inherent technological benefits of organic functional elements. For this issue, we invite research contributions reporting advances on topics such as the design/synthetic methods, structural characterization (including nanostructure), study of relevant properties (including morphological, physical, optical, electric, etc.) of macromolecules (single molecules, oligomers, polymers and dendrimers) aiming at their integration, e.g., through thin film processing (as roll-to-roll, inkjet printing, patterning techniques), as functional materials (including self-assembled materials and hybrid organic/inorganic materials) in devices, e.g., light-emitting diodes (LEDs), lasers, photodetectors, photovoltaic cells, transistors or others relevant devices suitable for flexible electronics.

Considering your outstanding contribution in this fascinating research filed, I would like to cordially invite you to submit a paper to this Special Issue.

Dr. Ana Charas
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

organic conductors and semiconductors
organic–inorganic hybrid semiconductors
structure-processing-property relationships
thin film processing
organic field-effect-transistors
organic light-emitting diodes
organic photovoltaics
transparent conducting electrodes
stability and lifetime of materials and devices

Published Papers (7 papers)

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Research

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14 pages, 3756 KiB

Open AccessFeature PaperArticle

Effect of the Number of Anchoring and Electron-Donating Groups on the Efficiency of Free-Base- and Zn-Porphyrin-Sensitized Solar Cells

by Raheleh Nasrollahi, Luis Martín-Gomis, Fernando Fernández-Lázaro, Saeed Zakavi and Ángela Sastre-Santos

Materials 2019, 12(4), 650; https://doi.org/10.3390/ma12040650 - 21 Feb 2019

Cited by 2 | Viewed by 3838

Abstract

A series of porphyrin compounds, free base (H₂P) and their Zn (II) metallated analogues (ZnP), bearing one, two or three carboxylic acid groups, have been synthesized, characterized, and used as sensitizers in dye sensitized solar cells (DSSCs). The performance of these devices has been analyzed, showing higher efficiencies of those sensitized with ZnP compounds. These results have been explained, on one hand, taking into account the electronic character of the metal ion, which acts as mediator in the injection step, and, on the other, considering the number of anchoring groups, which determines both the stereoelectronic character of the dye and the way it binds to TiO₂ surface. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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18 pages, 3039 KiB

Open AccessArticle

CuPc: Effects of its Doping and a Study of Its Organic-Semiconducting Properties for Application in Flexible Devices

by Mariel Leyva Esqueda, María Elena Sánchez Vergara, José Ramón Álvarez Bada and Roberto Salcedo

Materials 2019, 12(3), 434; https://doi.org/10.3390/ma12030434 - 31 Jan 2019

Cited by 9 | Viewed by 4656

Abstract

This study refers to the doping of organic semiconductors by a simple reaction between copper phthalocyanine and tetrathiafulvalene or tetracyanoquinodimethane. The semiconductor films of copper phthalocyanine, doped with tetrathiafulvalene donor (CuPc-TTF) and tetracyanoquinodimethane acceptor (CuPc-TCNQ) on different substrates, were prepared by vacuum evaporation. The structure and morphology of the semiconductor films were studied with infrared (IR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The absorption spectra for CuPc-TTF, recorded in the 200–900 nm UV–vis region for the deposited films, showed two peaks: a high energy peak, around 613 nm, and a second one, around 695 nm, with both peaks corresponding to the Q-band transition of the CuPcs. From the spectra, it can also be seen that CuPc-TTF has a B-band at around 330 nm and has a bandgap of approximately 1.4 eV. The B-band in the CuPc-TCNQ spectrum is quite similar to that of CuPc-TTF; on the other hand, CuPc-TCNQ does not include a Q-band in its spectrum and its bandgap value is of approximately 1.6 eV. The experimental optical bandgaps were compared to the ones calculated through density functional theory (DFT). In order to prove the effect of dopants in the phthalocyanine semiconductor, simple devices were manufactured and their electric behaviors were evaluated. Devices constituted by the donor-acceptor active layer and by the hollow, electronic-transport selective layers, were deposited on rigid and flexible indium tin oxide (ITO) substrates by the vacuum sublimation method. The current–voltage characteristics of the investigated structures, measured in darkness and under illumination, show current density values of around 10 A/cm² for the structure based on a mixed-PET layer and values of 3 A/cm² for the stacked-glass layered structure. The electrical properties of the devices, such as carrier mobility (μ) were obtained from the J–V characteristics. The mobility values of the devices on glass were between 1.59 × 10⁹ and 3.94 × 10¹⁰ cm²/(V·s), whereas the values of the devices on PET were between 1.84 × 10⁹ and 4.51 × 10⁹ cm²/(V·s). The different behaviors of the rigid and flexible devices is mainly due to the effect of the substrate. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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21 pages, 2984 KiB

Open AccessArticle

Bottom-Up Self-Assembled Supramolecular Structures Built by STM at the Solid/Liquid Interface

by Quirina Ferreira, Catarina L. Delfino, Jorge Morgado and Luís Alcácer

Materials 2019, 12(3), 382; https://doi.org/10.3390/ma12030382 - 25 Jan 2019

Cited by 15 | Viewed by 4587

Abstract

One of the lines of research on organic devices is focused on their miniaturization to obtain denser and faster electronic circuits. The challenge is to build devices adding atom by atom or molecule by molecule until the desired structures are achieved. To do this job, techniques able to see and manipulate matter at this scale are needed. Scanning tunneling microscopy (STM) has been the selected technique by scientists to develop smart and functional unimolecular devices. This review article compiles the latest developments in this field giving examples of supramolecular systems monitored and fabricated at the molecular scale by bottom-up approaches using STM at the solid/liquid interface. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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14 pages, 10694 KiB

Open AccessArticle

White-Light Emitting Di-Ureasil Hybrids

by Ming Fang, Lianshe Fu, Rute A. S. Ferreira and Luís D. Carlos

Materials 2018, 11(11), 2246; https://doi.org/10.3390/ma11112246 - 12 Nov 2018

Cited by 7 | Viewed by 3715

Abstract

White-light emitting materials have emerged as important components for solid state lighting devices with high potential for the replacement of conventional light sources. Herein, amine-functionalized organic-inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains codoped with lanthanide-based complexes, with Eu³⁺ and Tb³⁺ ions and 4,4′-oxybis(benzoic acid) and 1,10-phenanthroline ligands, and the coumarin 1 dye were synthesized by in situ sol–gel method. The resulting luminescent di-ureasils show red, green, and blue colors originated from the Eu³⁺, Tb³⁺, and C1 emissions, respectively. The emission colors can be modulated either by variation of the relative concentration between the emitting centers or by changing the excitation wavelength. White light emission is achieved under UV excitation with absolute quantum yields of 0.148 ± 0.015, 0.167 ± 0.017, and 0.202 ± 0.020 at 350, 332, and 305 nm excitation, respectively. The emission mechanism was investigated by photoluminescence and UV–visible absorption spectroscopy, revealing an efficient energy transfer from the organic ligands to the Ln³⁺ ions and the organic dye, whereas negligible interaction between the dopants is discerned. The obtained luminescent di-ureasils have potential for optoelectronic applications, such as in white-light emitting diodes. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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8 pages, 1863 KiB

Open AccessCommunication

Fullerene Aggregation in Thin Films of Polymer Blends for Solar Cell Applications

by Camilla Lindqvist, Ellen Moons and Jan Van Stam

Materials 2018, 11(11), 2068; https://doi.org/10.3390/ma11112068 - 23 Oct 2018

Cited by 5 | Viewed by 2651

Abstract

We report on the effects of the film morphology on the fluorescence spectra for a thin film including a quinoxaline-based co-polymer (TQ1) and a fullerene derivative ([6,6]-phenyl-C₇₁-butyric acid methyl ester—PC₇₀BM). The ratio between the polymer and the fullerene derivative, as well as the processing solvent, were varied. Besides the main emission peak at 700 nm in the fluorescence spectra of thin films of this phase-separated blend, a broad emission band is observed with a maximum at 520–550 nm. The intensity of this emission band decreases with an increasing degree of mixing in the film and becomes most prominent in thicker films, films with high PC₇₀BM content, and films that were spin-coated from solvents with lower PC₇₀BM solubility. We assign this emission band to aggregated PC₇₀BM. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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Review

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28 pages, 2777 KiB

Open AccessReview

Inorganic and Hybrid Perovskite Based Laser Devices: A Review

by Minas M. Stylianakis, Temur Maksudov, Apostolos Panagiotopoulos, George Kakavelakis and Konstantinos Petridis

Materials 2019, 12(6), 859; https://doi.org/10.3390/ma12060859 - 14 Mar 2019

Cited by 102 | Viewed by 8736

Abstract

Inorganic and organic-inorganic (hybrid) perovskite semiconductor materials have attracted worldwide scientific attention and research effort as the new wonder semiconductor material in optoelectronics. Their excellent physical and electronic properties have been exploited to boost the solar cells efficiency beyond 23% and captivate their potential as competitors to the dominant silicon solar cells technology. However, the fundamental principles in Physics, dictate that an excellent direct band gap material for photovoltaic applications must be also an excellent light emitter candidate. This has been realized for the case of perovskite-based light emitting diodes (LEDs) but much less for the case of the respective laser devices. Here, the strides, exclusively in lasing, made since 2014 are presented for the first time. The solution processability, low temperature crystallization, formation of nearly defect free, nanostructures, the long range ambipolar transport, the direct energy band gap, the high spectral emission tunability over the entire visible spectrum and the almost 100% external luminescence efficiency show perovskite semiconductors’ potential to transform the nanophotonics sector. The operational principles, the various adopted material and laser configurations along the future challenges are reviewed and presented in this paper. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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36 pages, 4280 KiB

Open AccessReview

Recent Developments in the Optimization of the Bulk Heterojunction Morphology of Polymer: Fullerene Solar Cells

by Hugo Gaspar, Flávio Figueira, Luiz Pereira, Adélio Mendes, Júlio C. Viana and Gabriel Bernardo

Materials 2018, 11(12), 2560; https://doi.org/10.3390/ma11122560 - 16 Dec 2018

Cited by 60 | Viewed by 6297

Abstract

Organic photovoltaic (OPV) devices, made with semiconducting polymers, have recently attained a power conversion efficiency (PCE) over 14% in single junction cells and over 17% in tandem cells. These high performances, together with the suitability of the technology to inexpensive large-scale manufacture, over lightweight and flexible plastic substrates using roll-to-roll (R2R) processing, place the technology amongst the most promising for future harvesting of solar energy. Although OPVs using non-fullerene acceptors have recently outperformed their fullerene-based counterparts, the research in the development of new fullerenes and in the improvement of the bulk-heterojunction (BHJ) morphology and device efficiency of polymer:fullerene solar cells remains very active. In this review article, the most relevant research works performed over the last 3 years, that is, since the year 2016 onwards, in the field of fullerene-based polymer solar cells based on the copolymers PTB7, PTB7-Th (also known as PBDTTT-EFT) and PffBT4T-2OD, are presented and discussed. This review is primarily focused on studies that involve the improvement of the BHJ morphology, efficiency and stability of small active area devices (typically < 15 mm²), through the use of different processing strategies such as the use of different fullerene acceptors, different processing solvents and additives and different thermal treatments. Full article

(This article belongs to the Special Issue From Macromolecules to Materials for Optoelectronic Devices)

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