No abstract

Solution-processable copolymers with pendant phosphorescent iridium complexes and 2,7-di(carbazol-9-yl)fluorene-type host moieties were synthesized using ruthenium-catalyzed ring-opening metathesis polymerization. Low polydispersity indices and molecular weights around 20 000 Da were obtained for all copolymers. As a result of the living character of the polymerization of the monomer containing the host moiety, a high degree of control over the molecular weights of all copolymers can be obtained. The photo-and electroluminescence properties of the copolymers were investigated. All copolymers retained the photo-and electrophysical properties of the corresponding nonpolymeric iridium complexes. Furthermore, as a proof of principle for the potential use of these materials, organic light-emitting devices were fabricated using the orange-emitting copolymer. A maximum external quantum efficiency of 1.9% at 100 cd/m 2 and a turn-on voltage of 3.7 V were obtained with photoluminescence quantum yield of 0.10 demonstrating the potential of these copolymers as emissive materials for display and lighting applications.

Passive radio frequency (RF) tags in the UHF and microwave bands have drawn considerable attention because of their great potential for use in many radio frequency identification (RFID) applications. However, more basic research is needed to increase the range and reliability of a passive RF tag's radio link, particularly when the RF tag is placed onto any lossy dielectric or metallic surface. This paper presents two new useful forms of the radio link budget that describe the power link of an RF tag system when the tag is attached to an object. These radio link budgets are dependent upon the gain penalty, a term which quantifies the reduction in RF tag antenna gain due to material attachment. A series of measurements, or radio assay, was used to measure the far-field gain pattern and gain penalty of several flexible 915 MHz antennas when attached to cardboard, pine plywood, acrylic, deionized water, ethylene glycol, ground beef, and an aluminum slab. It is shown that the gain penalty due to material attachment can result in more than 20 dB of excess loss in the backscatter communication link.

2,7‐Bis(p‐methoxyphenyl‐m′‐tolylamino)‐9,9‐dimethylfluorene (1′), 2,7‐bis(phenyl‐m′‐tolylamino)‐9,9‐dimethylfluorene (2′) and 2,7‐bis(p‐fluorophenyl‐m′‐tolylamino)‐9,9‐dimethylfluorene (3′) have been synthesized using the palladium‐catalyzed reaction of the appropriate diarylamines with 2,7‐dibromo‐9,9‐dimethylfluorene. These molecules have glass‐transition temperatures 15–20 °C higher than those for their biphenyl‐bridged analogues, and are 0.11–0.14 V more readily oxidized. Fluorescence spectra and fluorescence quantum yields for dimethylfluorene‐bridged and biphenyl‐bridged species are similar, but the peaks of the absorption spectra of 1′–3′ are considerably red‐shifted relative to those of their biphenyl‐bridged analogues. Time‐of‐flight hole mobilities of 1′–3′/polystyrene blends are in a similar range to those of the biphenyl‐bridged analogues. Analysis according to the disorder formalism yields parameters rather similar to those for the biphenyl species, but with somewhat lower zero‐field mobility values. Density functional theory (DFT) calculations suggest that the enforced planarization of the fluorene bridge leads to a slightly larger reorganization energy for the neutral/cation electron‐exchange reaction than in the biphenyl‐bridged system. Organic light‐emitting diodes have been fabricated using 1′–3′/polystyrene blends as the hole‐transport layer and tris(8‐hydroxy quinoline)aluminium as the electron‐transport layer and lumophore. Device performance shows a correlation with the ionization potential of the amine materials paralleling that seen in biphenyl‐based systems, and fluorene species show similar performance to biphenyl species with comparable ionization potential.