Hermann Schenk

Temperature stability of OLEDs using amorphous compounds with spiro-bifluorene core

The temperature stability of OLEDs was investigated by observing the I-V and EL-V characteristics of various devices stored at elevated temperature (up to 140 degrees Celsius). Results reported in this paper concern the standard KODAK structure for a green OLED (i.e. anode/CuPc/NPB/AlQ3/cathode), the standard IDEMITSU structure for a blue OLED (i.e. anode/CuPc/NPB/DPVBi/AlQ3/cathode) and variants of those using high Tg materials consisting of a spiro- bifluorene core. Use of Spiro-TAD as a hole transport material (HTM) and of Spiro-DPVBi as an emitting material (EM) resulted in considerable improvements. While the initial performance of the virgin devices is considerably unchanged, the temperature stability increases dramatically: for the green OLED no significant deterioration up to 140 degrees Celsius is found, compared to the standard device including NPB already starting to degrade slightly above 100 degrees Celsius; the blue OLED is stable up to approximately 120 degrees Celsius (particularly the color coordinates of the emitted light) whereas the standard device using DPVBi already deteriorates at around 80 degrees Celsius.

Development of high performance PPVs: implications of the polymer-microstructure

Poly(p-phenylene vinylene)s (PPVs) are promising materials for optoelectronic applications, especially for displays based on polymer light emitting diodes (PLEDs). We report here our findings concerning defect structures in this class of materials and the implications of the discovered irregularities on important material properties, that is, the operational life in a PLED. Recent improvements, which were deduced from this findings, are presented: optimized PPVs with a lower amount of defects result in a strong increase of operational lifetime.

51.1: Invited Paper: Polymers for Efficient OLEDs

Polymer light-emitting diodes (PLEDs) and displays based on polymer technology have made dramatic progress during the last years. In particular, efficiency and device lifetime have improved to such a significant extent that first products will commercialized within this year. We report here on the technical status of materials and devices upon which this success is based. Efficiency and especially operational stability are now at a level which easily meets the requirements for a variety of applications, namely power efficiencies are well above 10 lm/W, operational lifetimes are exceeding 20000 hours at display brightness levels and room temperature). This progress has been achieved by the careful analysis of failure mechanisms and the systematic improvement of materials. The first products, i. e. back-lights (for LCD-displays), segmented displays, and finally passive-matrix-addressed low-information-content (LIC) graphical displays are described. Light emitting polymerss are now manufactured on industrial scale under high purity conditions; filling and packaging is done under a class 10 clean room condition. For details see H. Becker Paper 46.1.

46.1: Industrial Manufacturing of High Performance PPVs for PLED Displays

Advances in the manufacturing of high purity, high performance PPVs are presented. The detailed understanding of the reaction mechanism of the Dehydrohalogenation-Polymerization (GILCH-Procedure) allows reliable manufacturing of high performance PPVs for display applications. The high efficiencies and long lifetimes of these materials facilitate market introduction of PLED displays. The light emitting polymers are now available on an industrial scale and are manufactured under high purity conditions, filling and packaging is done under class 10 clean room conditions.