Achieving Simultaneously Ultrahigh Brightness, Extremely Low Efficiency Roll‐Off and Ultralong Lifetime of Blue Fluorescent OLEDs by Using Donor–Acceptor‐Type 5,9‐Diarylamine Functionalized Pyrenes

Abstract

In this study, four new donor–acceptor (DA)‐type blue emitters (Py(5,9)BDPA, Py(5,9)BMTBA, Py(5,9)BDTBA, and Py (5,9)BTTBA) are developed by adopting benzene ring as A units and the diphenylamine (DPA) with different electron‐donating substituents as D units connected to 1,3‐positions and 5,9‐positions of pyrene ring, respectively. Gratifyingly, single‐crystal X‐ray analysis of the compounds demonstrates that the disgusting excimers in solid‐state could be effectively inhibited by the D units even the unsubstituted DPA resorting to the superiority of introducing D‐units at the 5,9‐positions of pyrene. The corresponding doped devices display ultrahigh luminance and extremely low efficiency roll‐off characteristics, especially for Py(5,9)BDPA, a roll‐off of external quantum efficiency is less than 4.9% when the luminance is up to 30 000 cd m−2, also showing good operation stability of devices. The optimized advanced device of the representative blue emitter Py(5,9)BDPA with a low manufacturing cost achieves extremely long LT95 (lifetime to 95% of the initial luminance) of 74 and 534 h at an initial luminance of 3000 and 1000 cd m−2, respectively. The ultralong lifetime of the emitter Py(5,9)BDPA is eye‐catching in the reported blue OLED lifetime and further demonstrates the practical applications in display and lighting of these DA‐type pyrene‐based blue emitters.

Aggregation behaviour of pyrene-based luminescent materials, from molecular design and optical properties to application

“…205 Recently, electron-donating substituents derived from diphenylamine were introduced at the 5,9-positions of pyrene. Compounds 90 199 display ultrahigh luminance and extremely low-efficiency roll-off characteristics with the maximum luminance of 48 280, 37 490, 37 850, and 44 450 cd m −2 with considerable EQE max of 4.30%, 4.31%, 4.06%, and 4.25% at a high luminance of ∼10 000 cd m −2 for 90a-90d , respectively. In addition, the high EQE may contribute to the high triplet exciton utilization efficiency (29% for 90a , 29% for 90b , 27% for 90c , and 28% for 90d ) via a triplet–triplet annihilation (TTA) process.…”

The Blue Problem: OLED Stability and Degradation Mechanisms

“…Reported OLED LT95 values, sampled focusing on blue devices, and reported lifetimes of OLEDs used in industry. ,,− ,,,− ,− ,− ,− …”

“…In another study, a donor–acceptor material based on pyrene Py­(5,9)­BDPA (Figure b) was used with α,β-ADN (Figure a) as the host to develop a TTA-UC OLED. It produced a blue color at (0.132, 0.27), and an extrapolated LT95 of 534 h; however, the EQE max was just over 4% . Another report disclosed a device with a LT95 of just under 500 h (LT50 of 8000 h) and an EQE max of 11.9% with a different pyrene-based compound as the emitter (Figure b) and CzPA (Figure b) as the host in a TTA-UC system .…”

“…It produced a blue color at (0.132, 0.27), and an extrapolated LT95 of 534 h; however, the EQE max was just over 4%. 60 Another report disclosed a device with a LT95 of just under 500 h (LT50 of 8000 h) and an EQE max of 11.9% with a different pyrene-based compound as the emitter ( Figure 2 b) and CzPA ( Figure 3 b) as the host in a TTA-UC system. 52 In terms of color, while the peak of the EL spectrum was at a reasonably blue 466 nm, it also included a strong, red-shifted component, likely arising from an aggregate state, and consequently the device emitted at CIE coordinates of (0.14, 0.16).…”