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Highlights: [•] SuperYellow shows a PLQY among the highest ever reported for a PPV-derivative polymer. [•] This higher photoluminescence has not been gained at the expense of carrier mobility. [•] Hole mobility measured both using the standard TOF and the charge generation layer TOF. [•] Mobility values are quite similar for both solution-cast and spin-coated films. [•] Charge transport is almost independent of the processing conditions for this material. [ABSTRACT FROM AUTHOR]

Abstract: 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/Vs 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”. [Copyright &y& Elsevier]

Many displays involve the use of color conversion layers. QDs are attractive candidates as color converters because of their easy processability, tuneable optical properties, high photoluminescence quantum yield, and good stability. Here, we show that emissive QDs with narrow emission range can be made in-situ in a polymer matrix, with properties useful for color conversion. This was achieved by blending the blue-emitting pyridine based polymer with a cadmium selenide precursor and baking their films at different temperatures. To achieve efficient color conversion, blend ratio and baking temperature/time were varied. We found that thermal decomposition of the precursor leads to highly emissive QDs whose final size and emission can be controlled using baking temperature/time. The formation of the QDs inside the polymer matrix was confirmed through morphological studies using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Hence, our approach provides a cost-effective route to making highly emissive color converters for multi-color displays. [ABSTRACT FROM AUTHOR]

The synthesis, characterization and evaluation in solid-state devices of a series of 8 cationic iridium complexes bearing different numbers of methoxy groups on the cyclometallating ligands are reported. The optoelectronic characterization showed a dramatic red shift in the absorption and the emission and a reduction of the electrochemical gap of the complexes when a methoxy group was introduced para to the Ir-C bond. The addition of a second or third methoxy group did not lead to a significant further red shift in these spectra. Emission maxima over the series ranged from 595 to 730 nm. All complexes possessing a motif with a methoxy group at the 3-position of the cyclometalating ligands showed very short emission lifetimes and poor photoluminescence quantum yields whereas complexes having a methoxy group at the 4-position were slightly blue shifted compared to the unsubstituted parent complexes, resulting from the inductively electron withdrawing nature of this directing group on the Ir-C bond. Light-emitting electrochemical cells were fabricated and evaluated. These deep red emitters generally showed poor performance with electroluminescence mirroring photoluminescence. DFT calculations accurately modelled the observed photophysical and electrochemical behavior of the complexes and point to an emission from a mixed charge transfer state. [ABSTRACT FROM AUTHOR]

A joint experimental and theoretical study of singlet exciton diffusion in spin-coated poly(3-hexylthiophene) (P3HT) films and its dependence on molecular weight is presented. The results show that exciton diffusion is fast along the co-facial π- π aggregates of polymer chromophores and about 100 times slower in the lateral direction between aggregates. Exciton hopping between aggregates is found to show a subtle dependence on interchain coupling, aggregate size, and Boltzmann statistics. Additionally, a clear correlation is observed between the effective exciton diffusion coefficient, the degree of aggregation of chromophores, and exciton delocalization along the polymer chain, which suggests that exciton diffusion length can be enhanced by tailored synthesis and processing conditions. [ABSTRACT FROM AUTHOR]

Phosphorescent poly(dendrimers) with a norbornene-derivedbackbonehave been synthesized using ring-opening metathesis polymerizationwith the Grubbs III catalyst. The dendrimers are comprised of a heterolepticiridium(III) complex core with two 2-phenylpyridyl ligands and a phenyltriazolylligand, biphenyl-based dendrons, and 2-ethylhexyloxy surface groups.The phenyltriazolyl ligand provides the attachment point to the polymerbackbone, and the two poly(dendrimers) differ in the number of dendronsattached to the 2-phenylpyridyl ligands. The poly(dendrimer) withone and two dendrons per ligand are termed mono- and doubly dendronized.The mono- and doubly dendronized poly(dendrimers) were found to haverelatively narrow polydispersities, around 1.4, viscosities approachingthose required for inkjet printing, and could be solution processedto form thin films. The dendrons played an important role in controllingthe photophysical properties of the materials. The parent homopolymerwith the same iridium(III) complex but no dendrons attached to theligands had a solution photoluminescence quantum yield (PLQY) of 48%.The solution PLQY was found to increase with increasing number ofdendrons with the mono- and doubly dendronized materials having solutionPLQYs of 65% and 71%, respectively. The increase in PLQY is due todecreased intrachain interchromophore interactions. A similar trendwas observed in the solid state with the parent, mono-, and doublydendronized polymers having film PLQYs of 2%, 44%, and 58%, respectively,demonstrating that both intra- and interchain interactions are controlledby the dendrons. [ABSTRACT FROM AUTHOR]

Exciton diffusion plays an important role in functional materials used in organic optoelectronic devices, such as solar cells, organic light emitting diodes, and lasers. Here we explore how exciton diffusion can be controlled in highly fluorescent blue‐emitting polyfluorene materials by changing the length and type of side chains. We find that the exciton diffusion coefficient (D) decreases from 1.2 × 10−3 cm2 s−1 to 0.2×10−3 cm2 s−1 when the side chain length is increased from 8 to 12 carbon atoms. Other changes to the side chains led to enhancement of D up to 1.6 × 10−3 cm2 s−1. Our results show that small adjustments to the molecular structure can be helpful for the future development of high‐brightness organic light emitting devices. Exciton diffusion measurements in highly fluorescent blue‐emitting polyfluorenes are reported. It is shown that the exciton diffusion coefficient can be tuned by up to a factor of 8 by the choice of side group. These results are important for high‐brightness organic light emitting diodes and lasers. [ABSTRACT FROM AUTHOR]