No abstract

Two series of copolyimides, poly(quinoxaline perylene bisimide)s and poly(quinoxaline perylene bisimide ether)s, carrying quinoxaline units and varying amounts of substituted perylene bisimides in the main chain have been synthesized. The polymers were characterized by FT-IR, NMR, UV/vis, and fluorescence spectroscopy as well as GPC, DSC, and TGA measurements. They are highly soluble in usual solvents like CHCl3, THF, etc., and form optically transparent films. The incorporation of varying amounts of perylene diimides with different substitution patterns allowed the control of fluorescence wavelength and intensity in solution and in thin films. The copolyimides with 1 mol % of perylene diimide content exhibit highest solid-state fluorescence. The observed intense fluorescence and a constant maximum wavelength of absorption in the solid state for copolymers containing up to 2.82 mol % perylene content indicate the absence of chromophore aggregation. Both types of copolymers are thermally stable up to 420 °C and exhibit glass transition temperatures in the range 225−270 °C. Blends of these perylene-containing polymers with hole transport molecules show complete photoluminescence quenching due to efficient electron transfer.

A combinatorial approach combining vapor deposition of organic molecules and a mask technique was used to prepare on one substrate a matrix of 49 organic light emitting diodes (OLEDs) with di †erent conÐgurations and layer thicknesses. A landscape library with two orthogonal, linear gradients of an emitter and a hole blocking electron transport material on top of a hole transport layer of constant thickness was prepared. The aim of this experiment was to investigate the inÑuence of an additional electron transport material on the efficiency. Using a semi-automated measurement set-up, the device parameters for each of the 49 OLEDs were evaluated. The existence of an optimum layer thickness for two-layer devices was Alq 3 ITO/TPD/Alq 3 /Al conÐrmed and such an optimized two-layer structure could not be improved by adding an additional hole blocking layer to the optimum layer. However, an improvement in photometric efficiency can be achieved Alq 3 by replacing the optimum layer thickness by certain combinations of layers. Alq 3 Alq 3 /spiro-quinoxaline Paper 8/09256G

In this paper polymeric light‐emitting diodes (LEDs) based on alkoxy‐substituted poly(p‐phenylene ethynylene) EHO‐OPPE as emitter material in combination with poly(triphenyldiamine) as hole transport material are demonstrated. Different device configurations such as single‐layer devices, two‐layer devices, and blend devices were investigated. Device improvement and optimization were obtained through careful design of the device structure and composition. Furthermore, the influence of an additional electron transporting and hole blocking layer (ETHBL), spiroquinoxaline (spiro‐qux), on top of the optimized blend device was investigated using a combinatorial method, which allows the preparation of a number of devices characterized by different layer thicknesses in one deposition step. The maximum brightness of the investigated devices increased from 4 cd/m2 for a device of pure EHO‐OPPE to 260 cd/m2 in a device with 25 % EHO‐OPPE + 75 % poly(N,N′‐diphenylbenzidine diphenylether) (poly‐TPD) as the emitting/hole‐transporting layer and an additional electron‐transport/hole‐blocking spiro‐qux layer of 48 nm thickness.

No abstract