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1.
Langmuir ; 33(39): 10118-10124, 2017 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-28873309

RESUMO

We demonstrate a facile approach to designing transparent electron-collecting electrodes by depositing thin layers of medium and low work function metals on top of transparent conductive metal oxides (TCOs) such as ITO and FTO. The modified electrodes were fairly stable for months under ambient conditions and maintained their electrical characteristics. XPS spectroscopy data strongly suggested integration of the deposited metal in the TCO structure resulting in additional doping of the conducting oxide at the interface. Kelvin probe microscopy measurements revealed a significant decrease in the ITO work function after modification. Organic solar cells based on three different conjugated polymers have demonstrated state of the art performances in inverted device geometry using Mg- or Yb-modified ITO as electron collecting electrode. The simplicity of the proposed approach and the excellent ambient stability of the modified ITO electrodes allows one to expect their wide utilization in research laboratories and electronic industry.

2.
Chem Commun (Camb) ; 53(35): 4830-4833, 2017 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-28418056

RESUMO

We report an unusual thermal condensation of readily available tetracyanocyclopropanes to tetracyanosubstituted triazaphenalenes, which revealed interesting optoelectronic properties such as strongly pronounced solvatochromism and bright photoluminescence. Optical memory elements and organic light emitting diodes with a deep red electroluminescence were designed using triazaphenalenes, thus highlighting the potential of these compounds as materials for electronic applications.

3.
ChemSusChem ; 8(24): 4209-15, 2015 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-26663820

RESUMO

The application of conjugated materials in organic photovoltaics (OPVs) is usually demonstrated in lab-scale spin-coated devices that are processed under controlled inert conditions. Although this is a necessary step to prove high efficiency, testing of promising materials in air should be done in the early stages of research to validate their real potential for low-cost, solution-processed, and large-scale OPVs. Also relevant for approaching commercialization needs is the use of printing techniques that are compatible with upscaling. Here, solution processing of organic solar cells based on three new poly(2,7-carbazole) derivatives is efficiently transferred, without significant losses, to air conditions and to several deposition methods using a simple device architecture. High efficiencies in the range between 5.0 % and 6.3 % are obtained in (rigid) spin-coated, doctor-bladed, and (flexible) slot-die-coated devices, which surpass the reference devices based on poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT). In contrast, inkjet printing does not provide reliable results with the presented polymers, which is attributed to their high molecular weight. When the device area in the best-performing system is increased from 9 mm(2) to 0.7 cm(2), the efficiency drops from 6.2 % to 5.0 %. Photocurrent mapping reveals inhomogeneous current generation derived from changes in the thickness of the active layer.


Assuntos
Carbazóis/química , Fontes de Energia Elétrica , Polímeros/química , Energia Solar , Ar , Peso Molecular , Tiadiazóis/química , Tiofenos/química
4.
Chem Commun (Camb) ; 51(35): 7562-4, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25848656

RESUMO

We report the application of a statistical Suzuki-Miyaura polycondensation reaction for synthesis of a family of carbazole-fluorene-TTBTBTT terpolymers with tailored physical and optoelectronic properties. Organic bulk heterojunction solar cells based on the designed materials with optimal fluorene to carbazole ratios yielded reproducible power conversion efficiencies of 6.5-6.7%.

5.
Chem Commun (Camb) ; 51(28): 6130-2, 2015 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-25748821

RESUMO

Optical memory elements based on photoswitchable organic field-effect transistors have been designed by using an interfacial layer of photochromic spirooxazine molecules sandwiched between semiconductor and dielectric layers. Optical and electrical programming of the designed devices leads to multiple discrete states demonstrating drastically different electrical characteristics (VTH, IDS) and advanced stability.

6.
Chem Commun (Camb) ; 51(12): 2239-41, 2015 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-25370184

RESUMO

Here we report the application of the Electron Spin Resonance (ESR) spectroscopy as a highly sensitive analytical technique for assessment of the electronic quality of organic semiconductor materials, particularly conjugated polymers. It has been shown that different batches of the same conjugated polymer might contain substantially different amounts of radical species which were attributed to structural defects and/or impurities behaving as traps for mobile charge carriers. Good correlations between the concentrations of radicals in various batches of conjugated polymers and their performances in organic solar cells have been revealed.

7.
Chem Commun (Camb) ; 51(12): 2242-4, 2015 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-25435101

RESUMO

It was shown that ESR spectroscopy is a very useful technique for monitoring the photochemical and thermal degradation of conjugated polymers commonly used in organic solar cells. The relative stability of materials can be quantified by comparing the rates of trap accumulation (dC(R)/dt) estimated from their ESR profiles.

8.
Chem Commun (Camb) ; 50(57): 7639-41, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-24893780

RESUMO

Here we report a systematic investigation of indigo thin films grown on different dielectric underlayers. It has been revealed that aliphatic hydrocarbon chains serve as templates inducing the formation of a new crystal modification of indigo which possesses advanced charge transport properties and affords a dramatic improvement in the electrical performance of organic field-effect transistors.

9.
Adv Mater ; 24(3): 375-80, 2012 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-22109816

RESUMO

Millenniums-old natural dye indigo--a "new" ambipolar organic semiconductor. Indigo shows balanced electron and hole mobilities of 1 × 10(-2) cm(2) V(-1) s(-1) and good stability against degradation in air. Inverters with gains of 105 in the first and 110 in the third quadrant are demonstrated. Fabricated entirely from natural and biodegradable compounds, these devices show the large potential of such materials for green organic electronics.


Assuntos
Produtos Biológicos/química , Corantes/química , Índigo Carmim/química , Semicondutores , Eletroquímica , Compostos de Estanho/química
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