Open Access Published by De Gruyter Open Access

Volume 4 Issue 1

January 2016

Issue of Organic Photonics and Photovoltaics

Contents
Journal Overview

Open Access April 25, 2016

Ultra-low p-doping of poly(3-hexylthiophene) and its impact on polymer aggregation and photovoltaic performance

Marcel M. Said, Yadong Zhang, Raghunath R. Dasari, Dalaver H. Anjum, Rahim Munir, Hanlin Hu, Aram Amassian, Stephen Barlow, Seth R. Marder

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Abstract

Poly(3-hexylthiophene) (P3HT) films and P3HT / fullerene photovoltaic cells have been p-doped with very low levels (< 1 wt. %) of molybdenum tris[1-(trifluoromethylcarbonyl)- 2-(trifluoromethyl)-ethane-1,2-dithiolene]. The dopants are inhomogenously distributed within doped P3HT films, both laterally and as a function of depth, and appear to aggregate in some instances. Doping also results in subtle changes in the local and long range order of the P3HT film. These effects likely contribute to the complexity of the observed evolutions in conductivity, mobility and work function with doping levels. They also negatively affect the open-circuit voltage and fill factor of solar cells in unexpected ways, indicating that dopant aggregation and non-uniform distribution can harm device performance.

Open Access December 5, 2016

Impact of scaling to the resistive switching effect in organic polymer – based structures

M.S. Kotova, M.A. Dronov, A.V. Rzhevskiy, S.V. Amitonov, T.V. Dubinina, V.E. Pushkarev, L.I. Ryabova, D.R. Khokhlov

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Abstract

The resistive switching effect has been studied in a set of organic polymer - based structures of a different composition and size scale from macro to micro. It is shown that scaling down reduces both the threshold switching voltage Vth and the respective effective electric field Eth. Furthermore, introduction of metal micro particles into a macro scale polymer matrix provides the same effect. Therefore the metal particle incorporation may be regarded as an alternative method of effective scaling, depending on an application. Switching speed of less than 15 ns, threshold voltage Vth ~ (2 – 25) V, 105 cycle endurance, no significant moisture dependence and high retention time 3.5 months for scaled down samples aswell as for metal doped macro samples have been demonstrated. These characteristics are suitable for constructing memory devices. The switching effect mechanisms are discussed.

Open Access December 5, 2016

Ultrafast electron and hole transfer in bulk heterojunctions of low-bandgap polymers

Oleg V. Kozlov, Vlad G. Pavelyev, Hilde D. de Gier, Remco W. A. Havenith, Paul H.M. van Loosdrecht, Jan C. Hummelen, Maxim S. Pshenichnikov

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Abstract

In modern bulk heterojunction (BHJ) organic solar cells, blends of low-bandgap polymer and [70]PCBM acceptor are used in the active layer. In this combination, the polymer absorbs photons from the red and near-IR parts of the solar spectrum, while the blue and near-UV photons are harvested by [70]PCBM. As a result, both electron transfer from polymer to [70]PCBM and hole transfer from [70]PCBM to polymer are of utmost importance in free charge generation and have to be optimized simultaneously. Here we study electron and hole transfer processes in BHJ blends of two low-bandgap polymers, BTT-DPP and PCPDTBT, by ultrafast photoinduced spectroscopy (PIA). By tracking the PIA dynamics, we observed substantially different charge separation pathways in BHJs of the two polymers with [70]PCBM. From the photoinduced anisotropy dynamics, we demonstrated that in the PCPDTBT:[70]PCBM system both electron and hole transfer processes are highly efficient, while in the BTTBPP:[ 70]PCBM electron transfer is blocked due to the unfortunate energy level alignment leaving hole transfer the only pathway to free charge generation. Calculations at the density functional theory level are used to gain more insight into our findings. The presented results highlight the importance of the energy level alignment on the charge separation process. Graphical Abstract

Open Access December 29, 2016

Synthesis, optical and electrochemical study of bipolar heterocyclic systems, including 1,2,4-oxadiazole moiety

D. G. Selivanova, O. A. Mayorova, A. A. Gorbunov, A. N. Vasyanin, M. V. Dmitriev, E. V. Shklyaeva, G. G. Abashev

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Abstract

Two new 3,5-dihetarylsubstituted 1,2,4- oxadiazoles 8 a,b, including N-alkyl substituted carbazole and thiophene moieties, were synthesized as potential components of materials for organic electronics devices. Optical and electrochemical properties of all new compounds were investigated. On the basis of the experimental UV absorption data, the values of bandgap energies equal to 3.44 eV (8a) and 3.05 eV (8b) were determined. The values of their ionization potentials, HOMO levels (−5.62 eV for 8a, −5.46 eV – for 8b), as well as their electron affinity levels, LUMO levels (−2.2 eV for 8a, −2.4 eV – for 8b), were calculated from the results of electrochemical studies. The energy of the triplet excited states of 8 a,b was defined with the help of time-dependent density functional theory (TD-DFT), comprising 2.68 eV (8a) and 2.32 eV (8b), where the greatest value of this parameter was for the compound with a shorter conjugation chain.

Open Access December 30, 2016

New chromophores based on combination of ethylenedioxythiophene and carbazole fragments: synthesis and optoelectronic properties

A.N. Bakiev, O.A. Mayorova, A.A. Gorbunov, I.V. Lunegov, E.V. Shklyaeva, G.G. Abashev

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Abstract

Two new D-π-A chromophores composed of an electron-donating carbazole unit linked through π- bridges, bearing 3,4-ethylenedioxythiophene (EDOT) moiety, with an electron withdrawing dicyanovinyl group (DCV) were successfully synthesized involving Suzuki or Heck cross-coupling and Knöevenagel reactions as the key steps. The obtained compounds absorb light over a broad spectral range, including the visible spectrum. The HOMO/LUMO energies and band gap energy values (Eg) were calculated on the basis of the experimental optical and electrochemical data: HOMO, LUMO, Eg (eV), −5.51, −3.14, 2.37 (4), −5.34, −3.14, 2.20 (7). The presence of the HC=CH unit in compound 7 resulted in the increase of the HOMO energy level, the decrease of a band gap value and red shifts of the absorption and emission bands in comparison with those of 4. Large Stokes shifts and broadband luminescence inherent to both chromophores suggest their use as materials for luminescent solar collectors (LSCs). The obtained compounds demonstrated good solubility and suitable thin-film forming properties. For this reason, they may be suitable for solution-processable photovoltaic applications.

Open Access December 30, 2016

Group 14 metalloles condensed with heteroaromatic systems

Joji Ohshita

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Abstract

There has been keen interest in group 14 metalloles as building units of conjugated organic functional materials. This short review summarizes our recent work on group 14 metalloles condensed with heteroaromatic systems, including thiophene and pyridine. These condensed metalloles show interesting properties depending on both the group 14 metallole elements and the heteroaromatic systems. High planarity of the condensed systems and interaction between the element σ*-orbital and the heteroaromatic π*-orbital enhance the conjugation in these systems leading to their potential applications as functional materials, such as carrier transporting materials and emissive materials.

Open Access December 30, 2016

Synthesis and luminescence of some rare earth metal complexes

Mikhail N. Bochkarev, Anatoly P. Pushkarev

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Abstract

In the present paper the synthesis, photoand electroluminescent properties of new rare earth metal complexes prepared and studied at the Razuvaev Institute of Organometallic Chemistry during the last decade are reviewed. The obtained compounds give luminescence in UV, visible and NIR regions. The substituted phenolates, naphtholates, mercaptobenzothiazolate, 8-oxyquinolinolate, polyfluorinated alcoholates and chalcogenophosphinates were used as ligands. The synthesis and structure of unusual three–nuclear sulfidenitride clusters of Nd and Dy are described. The new excitation mechanism of ytterbium phenolates and naphtholates, which includes the stage of reversible reduction of Yb to divalent state and oxidation of the ligands in the excitation process, is discussed.

Open Access December 30, 2016

Plausible role of nanoparticle contamination in the synthesis and properties of organic electronic materials

Valentine P. Ananikov

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Abstract

Traceless transition metal catalysis (Pd, Ni, Cu, etc.) is very difficult to achieve. Metal contamination in the synthesized products is unavoidable and the most important questions are: How to control metal impurities? What amount of metal impurities can be tolerated? What is the influence of metal impurities? In this brief review, the plausible origins of nanoparticle contamination are discussed in the framework of catalytic synthesis of organic electronic materials. Key factors responsible for increasing the probability of contamination are considered from the point of view of catalytic reaction mechanisms. The purity of the catalyst may greatly affect the molecular weight of a polymer, reaction yield, selectivity and several other parameters. Metal contamination in the final polymeric products may induce some changes in the electric conductivity, charge transport properties, photovoltaic performance and other important parameters.

About this journal

The Organic Photonics and Photovoltaics (OPP) journal has been closed since the beginning of the 2019.

The journal covered topics of the most important advances in the chemistry, physics, materials science, and engineering of organic photo-active materials for primary applications in photovoltaic cells but extending other photonic devices involving the generation, propagation, detection, and processing of light. Papers The journal was published in Open Access model and is archived in Portico.

All authors retain copyright, unless – due to their local circumstances – their work is not copyrighted. The copyrights are governed by the Creative-Commons license.