A new route to ladder-type pentaphenylenes has been developed in which both good hole-accepting p-type and electron-accepting n-type materials can be prepared from a common intermediate. This key intermediate is a pentaphenylene diester 5 obtained in high yield by Suzuki coupling of 2 equiv of fluorene boronates with 2,5-dibromoterephthalate. Addition of aryllithium followed by ring closure with boron trifluoride produced a blue-emitting ladder-type pentaphenylene. Bromination followed by reductive polymerization with nickel(0) gave new high molecular mass polymers, which show efficient blue emission with a very small Stokes shift. These polymers bridge the gap in emission between polyfluorenes and fully ladder-type polyphenylenes. An alternative ring closure of the dibromopentaphenylene diester 14 with acid made a diketone that is a good electron-accepting material, as it displays a reversible two-electron reduction. The reduction onset potential of -0.875 V against Ag/Ag(+) corresponds to a lowest unoccupied molecular orbital (LUMO) energy level of 3.53 eV, comparable to the work function of magnesium, suggesting that this unit could be used to greatly increase the injection of electrons into polymers containing it in a light-emitting diode (LED) or solar cell. A red-emitting material was prepared by Suzuki coupling of the dibromopentaphenylene 10b with a perylene dye, thus offering the prospect of tuning the emission from pentaphenylene materials over the whole visible range by attachment of suitable dyes. Unoptimized single-layer organic LEDs that used 11b showed stable pure-blue emission with brightnesses of over 200 cd/m(2) at 7 V, with moderate efficiencies.

A unique implementation of an organic image detector using resistive photo-switchable pixels is presented. This resistive photo-switch comprises the vertical integration of an organic photodiode and an organic resistive switching memory element. The photodiodes act as a photosensitive element while the resistive switching elements simultaneously store the detected light information.

Pyrene is one of the most important and thoroughly investigated organic chromophores. Among the attractive features of pyrene is its exceptionally long fluorescence lifetime, [1] the sensitivity of its excitation spectra to microenvironment changes, [2] and its high propensity for forming excimers. [3] This excimer formation has been utilized over the last 50 years in the investigation of water-soluble polymers, making pyrene, by far, the most frequently applied dye in fluorescence-labeled polymers. [4] Despite its chemical stability and high charge carrier mobility, its strong tendency to form excimers leads to a red-shift of its emission as well as a decrease in its fluorescence efficiency in condensed media, which has prohibited its use as an emissive material in organic light-emitting devices (OLED)s.Since the report of the first double-layer thin-film OLED by the Kodak Company in 1987, [5] OLEDs have attracted enormous attention in the scientific community thanks to their high technological potential for the next generation of fullcolor-flat-panel displays and lighting applications. [6,7] Whether polymers [8] or small molecules, [5] to date only red-and greenemitters have shown sufficient efficiencies and lifetimes to be of commercial value. [7] Here, we present a novel non-aggregating polypyrene, which can be synthesized via a simple three-step chemical route from pyrene in good yields. Our poly-7-tert-butyl-1,3-pyrenylene (3) shows a high solid-state fluorescence quantum yield with blue emission, excellent solubility and stability, no aggregation in thin films, and good electro-optical performance in single-layer OLEDs.The use of pyrene, a large conjugated aromatic system, as emitting material in OLED applications has been limited, due to aggregation between planar pyrene molecules. The formation of p-aggregates/excimers causes the quenching of fluorescence, resulting in low solid-state fluorescence quantum yields. In recent years, there has been an increasing interest in the use of pyrene units in OLEDs, including oligothiophenes with pyrenyl side groups, [9] bipyrenylbenzene molecules, [10] as well as pyrene-carbazole [11] and pyrene-fluorene systems, [12,13] due to their emissive properties combined with high charge carrier mobility. However, the pyrene derivatives that have been reported so far as efficient blue-emitters for OLED applications still present some degree of aggregation in the solid state. [13] A successful effort in the prevention of aggregation in small molecules was achieved with tetrasubstituted, highly sterically hindered pyrenes, which can emit blue light in solution as well in the solid state and with high quantum yield.[14] The well-known 1,3,6,8-tetraphenylpyrene, for example, has been used in OLEDs, [14] organic field-effect transistors (OFET)s, [15] as well in organic light-emitting field-effect transistors (OLEFET)s. [16] Additional tetrasubstituted systems including different phenyl derivatives [14] or pyridyl units [17] at the 1-, 3-, 6-, and 8-positions have been reported ...

An all‐solution processed organic light‐emitting diode with enhanced device efficiency based on an additional methanol‐soluble polyfluorene layer (see figure) with nonionic ethylene glycol side chains is presented. Due to an asymmetric shift of the energy levels at the polymer/polymer interface, significant efficiency enhancements were obtained.