Improved performance in the aged electron-only devices based on tris-(8-hydroxyquinoline) aluminum thin film as electron transport layer for OLED applications

Abstract

We fabricated the electron-only devices (EODs) based on tris-(8-hydroxyquinoline) aluminum (Alq3) as an electron transport layer (ETL) with the structure of ITO/Alq3 as ETL/LiF/Al and the devices were exposed under the normal ambient for various time periods of aging. The EODs after 6 hrs of aging showed the higher electron current density (1.516 mA/cm2 at 4 V, 3.472 mA/cm2 at 6V, and 6.443 mA/cm2 at 8V) when compared to that (0.406 mA/cm2 at 4V, 0.582 mA/cm2 at 6V, and 5.18 mA/cm2 at 8V) of pristine EOD device. The TRPL spectra of pristine and aged (under the normal ambient) Alq3 samples show the decrease of PL decay lifetimes as the aging period increases, which is consistent with the decreased device performances of the further aged devices. The improved device electrical performance of the 6 hrs aged EODs may be attributed to the improved interface properties in the device upon biasing of the pristine device. It is reported that upon aging the luminescent quencher (carbonyl group) formed in the Alq3 i...