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Saint Andrews, United Kingdom

Wang Y.,Organic Semiconductor Center | Tsiminis G.,Organic Semiconductor Center | Yang Y.,Organic Semiconductor Center | Ruseckas A.,Organic Semiconductor Center | And 6 more authors.
Synthetic Metals | Year: 2010

We report amplified spontaneous emission (ASE) and optically pumped deep-blue-emitting distributed feedback (DFB) lasers based on a star-shaped oligofluorene truxene molecule. A low ASE threshold of 2.1 kW/cm2 at 439 nm was achieved. The material exhibits a high net gain of 38 cm-1 and also low optical loss coefficient of 3.5 cm-1. Second-order DFB lasers show tuning of the emission wavelength from 422 to 473 nm, and a minimum threshold density of 515 W/cm2. This is the broadest tuning range (51 nm) reported for organic deep-blue/blue lasing materials. © 2010 Elsevier B.V. All rights reserved. Source


Ribierre J.C.,Organic Semiconductor Center | Yates C.J.,Organic Semiconductor Center | Ruseckas A.,Organic Semiconductor Center | Staton S.V.,University of Oxford | And 2 more authors.
Organic Electronics: physics, materials, applications | Year: 2010

We present evidence that the photoluminescence (PL) spectrum, PL kinetics and PL efficiency of solution-cast films of a phosphorescent fac-tris(2-phenylpyridyl)iridium(III)-cored dendrimer are not affected by the choice of solvent and thermal annealing. In contrast, when the dendrimer is dispersed into a 4,4′-bis(N-carbazolyl)biphenyl (CBP) host, thermal annealing induces phase separation at a micrometer scale, which results in incomplete energy transfer from CBP to the dendrimer. The insensitivity of the dendrimer film morphology and PL properties to the casting conditions and thermal treatment shows the advantage of host-free electrophosphorescent dendrimers for the further development of light-emitting displays, whilst blended systems are potentially more suitable for photovoltaic applications. © 2009. Source


Stevenson J.R.Y.,Organic Semiconductor Center | Lattante S.,University of Salento | Andre P.,Organic Semiconductor Center | Andre P.,RIKEN | And 2 more authors.
Applied Physics Letters | Year: 2015

We demonstrate a static fabrication approach to make free-standing ordered arrays of fluorescent nanofibres through control of the transverse electrospinning field. The alignment and the density of the nanofibre arrays are optimised by careful design of both the source and collector electrode geometries which can control the transverse electric field over the full path of the jet. In doing so, we fabricate suspended fluorescent nanofibres with an aspect ratio of 104, and with a substantially increased density and order parameter (by a factor of ∼10 compared to random deposition). Electrostatic modelling suggests that the field distribution of the component is the main contribution to the ordering between the plates. This method offers increased efficiency for the creation of ordered fibres collected over a small area and the characterisation of their photoluminescent properties. © 2015 AIP Publishing LLC. Source


Dalgarno P.A.,Organic Semiconductor Center | Traina C.A.,University of California at Santa Barbara | Penedo J.C.,Organic Semiconductor Center | Penedo J.C.,University of St. Andrews | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

The photophysical behavior of conjugated polymers used in modern optoelectronic devices is strongly influenced by their structural dynamics and conformational heterogeneity, both of which are dependent on solvent properties. Single molecule studies of these polymer systems embedded in a host matrix have proven to be very powerful to investigate the fundamental fluorescent properties. However, such studies lack the possibility of examining the relationship between conformational dynamics and photophysical response in solution, which is the phase from which films for devices are deposited. By developing a synthetic strategy to incorporate a biotin moiety as a surface attachment point at one end of a polyalkylthiophene, we immobilize it, enabling us to make the first single molecule fluorescence measurements of conjugated polymers for long periods of time in solution. We identify fluctuation patterns in the fluorescence signal that can be rationalized in terms of photobleaching and stochastic transitions to reversible dark states. Moreover, by using the advantages of solution-based imaging, we demonstrate that the addition of oxygen scavengers improves optical stability by significantly decreasing the photobleaching rates. © 2013 American Chemical Society. Source


Gambino S.,Organic Semiconductor Center | Bansal A.K.,Organic Semiconductor Center | Samuel I.D.W.,Organic Semiconductor Center
Organic Electronics: physics, materials, applications | Year: 2010

The problem that conventional time of flight (TOF) mobility measurements are made on much thicker films than typically used in organic optoelectronic devices is investigated by comparing the mobility of thick and thin films of the poly(phenylenevinylene) based copolymer "SuperYellow". We report for the first time mobility values perpendicular to the substrate for this widely used material and find them to be of the order of 10-6-10-7 cm2/V s for both spin-coated and drop-cast films. A high photoluminescence quantum yield (PLQY) of 60 ± 5% is measured for both types of films. The results indicate a trade-off between PLQY and charge transport in poly(arylenevinylene)s. The insensitivity of the charge transporting and photophysical properties to the film preparation procedure and thickness is a desirable characteristic that may result from the bulky side groups of "SuperYellow". © 2009 Elsevier B.V. All rights reserved. Source

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