The authors report on highly efficient phosphorescent organic light-emitting diodes (OLEDs) based on a low-molecular weight electron-conducting, bis-spirobifluorene host doped with a soluble derivative of the green emitter fac-tris(2-phenylpyridine) iridium (III) [Ir(ppy)3]. All organic layers were spin coated and a strong improvement of performance was achieved by introduction of a hole-transporting double layer based on cross-linkable low-molecular weight molecules. The devices combine the easy fabrication procedure known from polymer-based OLEDs with the higher efficiency of small molecules. Maximum luminous and power efficiencies of 59cd∕A and 58lm∕W, respectively, are obtained, combined with a low driving voltage and high efficiencies even at high brightnesses. At 1000cd∕m2 the efficiencies are as high as 55cd∕A and 49lm∕W.

Transition-metal complexes in organic light-emitting diodes (OLEDs) can overcome the efficiency limit of fluorescent devices. Due to the strong spin-orbit coupling of these complexes, both singlet and triplet excitons can be harvested and an internal quantum efficiency of 100 % is possible.[1-3] Many complexes with transition-metals, such as iridium, ruthenium, osmium and platinum have been synthesized to develop highly efficient phosphorescent OLEDs (PHOLEDs), [4][5][6][7][8] because a simple ligand-variation allows for a wide range of emission-colors and for tuning of the chemical properties.

Enlightening the memory: The integration of a crosslinkable photochromic dithienylperfluorocyclopentene (DTE) into organic light-emitting diodes (OLED) allows for the individualization of the emissive area of the OLED device, for example, for signage applications. The operation principle is based on switching the injection barrier for holes (positive charge carriers). Very large ON/OFF ratios of up to 3000 for current as well as electroluminescence have been achieved.

New 4-fold alkoxy-substituted poly(p-phenylene-ethynylene)-alt-poly(p-phenylene-vinylene) polymers (PPE-PPV) have been synthesized in order to elucidate the previously observed effect of side chains on the thin film properties (i.e., color variation) of PPE-PPVs. The length of the side chains attached to the PPE segments, C n H 2n+1 , has been varied from n ) 12 to 19. The side chains attached to the PPV segments have been kept fixed to C 8 H 17 . Polymers with n < 16 are yellow in color, whereas those with n g 16 are orange. Differential scanning calorimetry and nanoindentation analyses reveal side chain crystallization above room temperature in samples with longer side chains (n g 16). Reorganization of the longer side chains attached to the PPE units seems to support stronger π-π overlap between the chain backbones. The red shift for n g 16 was confirmed by photoluminescence (PL) and electroluminescence (EL) spectra obtained for inkjet printed and spin-coated thin films. However, the obtained orange-red EL emission colors are unstable upon increase of the applied voltage. A blue shift of up to 100 nm was observed. All the polymers exhibited very high relative and absolute PL quantum yields in solution (∼70%). Their solid-state absolute PL quantum yield was found to be between 10 and 20%. Polymeric light emitting diodes (PLED) with the following structure ITO//PEDOT:PSS//Pn/8//Ca//Ag were fabricated. The devices were fully characterized and showed low turn-on voltages.