Although the electroluminescence (EL) stability of phosphorescent organic light-emitting devices (PHOLEDs) has long been known to depend on the stability of the phosphorescent guest emitter, we recently found that the host also plays an important role. More specifically, we found that interactions between excitons and polarons to result in molecular aggregation of the host material, a phenomenon that appears to play a significant role in the deterioration in efficiency with electrical aging in these devices. The question of whether it is the guest or the host that plays the more leading role in device stability becomes therefore quite relevant. In this work we present data from a comparative systematic study on various host and guest materials used in PHOLEDs. The host materials include CBP, 26DCzPPy and TAPC, and the guest materials include Ir(ppy)3, Ir(ppy)2(acac), Ir(piq)3 and FIrpic. Changes in EL and time resolved photoluminescence characteristics are used in order to understand the interplay between the host and the guest under various electrical and thermal stress conditions. Results suggest that the host plays a more dominant role in determining PHOLED stability. They also shed some light on the interplay between host and guest materials and the effect on device stability. Results from this work will be presented and analyzed.

Date Published: 4 November 2016
PDF: 1 pages
Proc. SPIE 9941, Organic Light Emitting Materials and Devices XX, 99410Q (4 November 2016); doi: 10.1117/12.2237857

Published in SPIE Proceedings Vol. 9941:
Organic Light Emitting Materials and Devices XX
Franky So; Chihaya Adachi; Jang-Joo Kim, Editor(s)