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Viewing upcoming talks containing the keyword: 12
Speaker: Mr Bernd Ebenhoch (University of St Andrews)
Organic solar cells have great potential for cost-effective and large area electricity production, but their applicability is limited by the relatively low efficiency. In this talk I report investigations of novel materials and the underlying principles of organic solar cells. I will show that â‘ the charge carrier mobility of organic semiconductors in the active layer of polymer solar cells has a rather small influence on the power conversion efficiency. Cooling solar cells of the polymer:fullerene blend PTB7:PC71BM from room temperature to 77 K decreased the hole mobility by a factor of thousand but the device efficiency only halved. â‘¡Subphthalocyanine molecules, which are commonly used as electron donor materials in vacuum-deposited active layers of organic solar cells, can, by a slight structural modification, also be used as efficient electron acceptor materials in solution-deposited active layers. These acceptors offer, compared to standard fullerene acceptors, advantages of a stronger light absorption at the peak of the solar spectrum. â‘¢A low band-gap polymer donor material requires a careful selection of the acceptor material in order to achieve efficient charge separation and a maximum open circuit voltage. â‘£The use of a processing additive in the casting solution for the active layer of organic solar cells of PTB7:PC71BM strongly influences the morphology, which leads not only to an optimum of charge separation but also to optimal charge collection.
On: July 9, 2015 From: 13h00 To: 14h00View talk
Speaker: Prof Bart Jan Ravoo (University of Muenster)
Selfâ€assembly is emerging as a superior method to prepare adaptive and responsive nanomaterials. Responsive multivalent interactions are key to such versatile materials. This lecture will highlight soft material composed of cyclodextrins and/or superparamagnetic nanoparticles. It will be shown that using the hostâ€guest chemistry of cyclodextrins, we can form hydrogels as well as nanocapsules. We can also make “magnetic vesicles” that selfâ€assemble in microscale linear aggregates in aqueoussolution under the influence of a magnetic field. The metastable linear aggregates can be stabilized by a noncovalent and photoresponsive crossâ€linker, which can be photoisomerized between an adhesive and a nonadhesive configuration. Thus, the hybrid material responds to magnetic field as well as to light and a stable selfâ€assembled structure can only be obtained in a magnetic field in the presence of the noncovalent crossâ€linker. We have recently extended this strategy to superparamagnetic nanoparticles modified with cyclodextrin. These hybrid nanoparticles can befurther functionalized using host guest interaction and molecular recognition and they can be used to capture and isolate proteins.
References:1. A. Samanta, B. J. Ravoo, Angew. Chem. Int. Ed. 2014, 53, 12946–12950.2. S. Himmelein, V. Lewe, M. C. A. Stuart, B. J. Ravoo, Chem. Sci. 2014, 5, 1054â€1058.3. J. H. Schenkel, A. Samanta, B. J. Ravoo, Adv. Mater. 2014, 26, 1076–1080.
On: August 24, 2015 From: 15h30 To: 16h30View talk
Speaker: Prof Osamu Ishitani (Tokyo Institute of Technology)
Both the problems of the global warming and shortage of the fossil fuels have brought about great interest in photochemical utilization of CO2 with solar energy. Efficient photocatalysts for CO2 reduction must be necessary for development of such an important technology.
We have developed novel types of photocatalytic systems using metal complexes and/or semiconductors as a photocatalyst.1 In this presentation, I will focus on the architecture of two types of the photocatalysts using transition metal complexes:
(1) A mixed photocatalytic system including a ring-shaped Re(I) multinuclear complex as a photosensitizer2
(2) Ru(II)-Re(I) and Ru(II)-Re(I) supramolecular photocatalysts.3
The efficiency of the former photocatalytic system has been highest in the reported CO2-reduction photocatalysts (ï† = 82%), and the latter photocatalysts have been most robust (TON > 3000).
On: September 11, 2015 From: 15h30 To: 16h30View talk
Physics and Astronomy Colloquia
Speaker: Professor Isabelle Ledoux-Rak (Laboratoire de Photonique Quantique et MolÃ©culaire, Ecole Normale SupÃ©rieure de Cachan, France)
2015 Holweck Prize Lecture
Joint Physics/Chemistry Colloquium
The emergence of molecular photonics at the cross-roads of physics, chemistry and device engineering has being triggered by increasing demand in various fields such as high bitrate telecommunications, sensors, and bio-imaging. The wealth of molecular structures and the exploitation of their functional and structural flexibility opens-up new, exciting horizons for this area of research. Designing highly efficient molecules with optimised photonic properties remains a major challenge after 50 years of continuous development, based on fruitful and interdisciplinary cooperation between chemists and physicists.
In this lecture, the principles of molecular engineering for quadratic nonlinear optics will be discussed, with an emphasis on metal complexes and lanthanide derivatives, on nonlinear optical characterization methods. This will be followed by a review of intermolecular interactions and various orientation methods, in order to bridge the gap between molecules to materials, towards a wide range of applications. Finally, perspectives will be provided on molecular photonics towards device–rel.
On: September 16, 2015 From: 17h15 To: 18h30View talk
Speaker: Dr Roger De Souza (RWTH Aachen)
There is renewed interest in the behaviour of point defects in bulk SrTiO3 and at its extended defects due to the material's possible application in all-oxide electronics and as a memristive device. The combination of 18O/16O exchange and Secondary Ion Mass Spectrometry (SIMS) analysis constitutes a powerful tool for probing the behaviour of oxygen vacancies in oxides. In this contribution, after a brief introduction to the technique and its capabilities and limitations, I demonstrate the application of this method to investigating the behaviour of oxygen vacancies in SrTiO3 and at its extended defects (dislocations, surfaces, hetero-interfaces). Three systems will be examined: (1) single crystal SrTiO3 substrates; (2) low-angle grain boundaries in SrTiO3 comprising periodic arrays of edge dislocations; and (3) thin films samples. In general, I will emphasize the need to combine experimental and computational approaches, and I will draw attention to current challenges and outstanding problems.
On: September 30, 2015 From: 15h30 To: 16h30View talk