Inside Front Cover: Polarized‐Light‐Emitting Quantum‐Rod Diodes (Adv. Mater. 11/2005)

Polarized‐light‐emitting quantum‐rod diodes have been successfully produced using thin layers of quantum rods oriented by a rubbing technique, as shown on the inside cover. Hikmet and co‐workers report on p. 1436 that diode emission at 620 nm with a luminance efficiency of 0.65 cd A^–1 and an external quantum efficiency of 0.49 % is obtained. Light emitted polarized parallel to the long axis of the rods is 1.5 times more intense than that polarized perpendicular to the rods.     

OLEDs: Degradation Mechanisms in Small‐Molecule and Polymer Organic Light‐Emitting Diodes (Adv. Mater. 34/2010)

Degradation in organic light‐emitting diodes (OLEDs) is a complex problem. Depending upon the materials and the device architectures used, the degradation mechanism can be very different. In this Progress Report, using examples in both small molecule and polymer OLEDs, the different degradation mechanisms in two types of devices are examined. Some of the extrinsic and intrinsic degradation mechanisms in OLEDs are reviewed, and recent work on degradation studies of both small‐molecule and polymer OLEDs is presented. For small‐molecule OLEDs, the operational degradation of exemplary fluorescent devices is dominated by chemical transformations in the vicinity of the recombination zone. The accumulation of degradation products results in coupled phenomena of luminance‐efficiency loss and operating‐voltage rise. For polymer OLEDs, it is shown how the charge‐transport and injection properties affect the device lifetime. Further, it is shown how the charge balance is controlled by interlayers at the anode contact, and their effects on the device lifetime are discussed.     

Cover Picture: Multilayer Polymer Light‐Emitting Diodes: White‐Light Emission with High Efficiency (Adv. Mater. 17/2005)

White‐light‐emitting polymer diodes can be fabricated by solution processing using a blend of luminescent semiconducting polymers and organometallic complexes as the emission layer, and water‐soluble (or ethanol‐soluble) polymers and/or small molecules as the hole‐injection/transport layer (HIL/HTL) and the electron injection/transport layer (EIL/ETL), as reported on p. 2053 by Gong, Bazan, Heeger and co‐workers. Illumination‐quality light is obtained from these multilayer, high‐performance devices, with stable CIE coordinates, color temperatures, and high color‐rendering indices all close to those of “pure” white light. The cover illustration envisages the incorporation of the fabrication technique with low‐cost manufacturing technology in order to produce large areas of high‐quality white light.