Exceeding 10 000 h of Lifetime in Blue Fluorescent Organic Light‐Emitting Diodes by Introducing an Electron Leakage Pathway

Abstract

Electron leakage is one of the most critical factors for the degradation of blue fluorescent organic light‐emitting diodes (FOLEDs), as it occurs when electrons injected from the cathode flow to an electron‐blocking layer (EBL) without being entirely consumed within an emissive layer (EML). To address this issue, this study introduces the concept of an electron leakage‐pathway (ELP). Anthracene core materials, used as hosts for blue FOLEDs were doped in the EBL to prevent its direct damage to the EBL molecules by constructing the ELP. This study shows that using an anthracene core with high bond dissociation energy (BDE) in the anionic state as the ELP is the most effective way to increase the lifetime of the FOLED, demonstrating over 400 h. of LT90 (the time taken for the luminance to decrease to 90% of its initial value), which corresponds to an increase of 33% compared to the lifetime without the ELP. Remarkably, under a commonly used brightness level of 500 cd m−2 in smartphones, an LT50 of over 10 000 h was obtained. Ultimately, this study outlines a strategy for increasing the lifetime of blue FOLEDs through simple modifications to the device structure, without requiring the development of EBL materials or complex device engineering.

Colour-tuning of multiple resonance thermally activated delayed fluorescence emitters for hyperfluorescence with long-lifetime device characteristics

“…In addition to the effects of FETs and DETs, the difference in lifetime between devices A2 and A4 can be attributed to molecular degradation due to electron injection. 50 In particular, 4CzIPN and TCz-4mCNTrz have a donor–acceptor type TADF structure, and the bond between the donor and acceptor is composed of C–N bonds. However, the injected electrons easily degrade the C–N bonds, leading to a shortened lifetime.…”