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CPP: Chemische Physik und Polymerphysik

CPP 23: POSTER Functional Organic Thin Films

CPP 23.42: Poster

Donnerstag, 30. März 2006, 17:00–19:00, P2

Temperature Stability of Organic Light Emitting Diodes — •Philipp Wellmann, Michael Hofmann, Ansgar Werner, André Grüßing, Michael Limmert, Andrea Lux, and Jan Birnstock — Novaled GmbH, Tatzberg 49, 01307 Dresden, Germany

Organic Light Emitting Diodes (OLED) have received much attention during the last years and are now approaching mass production. Using the so-called PIN-Technology (p- and n-doped transport layers) we have demonstrated a combination of very low driving voltage, high efficiency and long lifetime. However, for applications (especially for automotive) a high temperature stability is an important issue. A well know material combination for n-doping is BPhen (4,7-diphenyl-1,10-phenanthroline) doped with pure Cs in a co-evaporation process. However, this system is known to have a low temperature stability. BPhen has a Tg of approx. 65^∘C and the conductivity of n-doped BPhen quickly decreases at temperatures about 70^∘C. Using improved host materials and newly developed organic dopands, we have been able to increase Tg and the thermal stability of our n-doped transport layers significantly. A storage test at 110^∘C leads to a significant increase in driving voltage and strongly decreased efficiency for BPhen:Cs, whereas the OLEDs using a molecular dopand stay essentially unchanged. The operational lifetime of PIN-OLEDs has strongly increased in the last year reaching values of more then 20.000h for red /green and 5.000h for a deep blue at 500 cd/m2 and room temperature. Using our molecular doping we have now been able to demonstrate a lifetime of more then 6.000h at 500 cd/m2 at 80^∘C.