P‐184: Boron Derivatives as Deep Blue Fluorescent Materials for High Efficiency and Long Lifetime

Abstract

Deep blue fluorescent organic light-emitting diodes were developed using boron derived 5emitters rather than thermally activated delayed fluorescent emitters for long lifetime. The DABNA and t-DABNA boron emitters were doped in a 9,10-bis (1-naphtyl) anthracene (-ADN) host to harvest singlet excitons only and stabilize triplet excitons for long periods. The t-DABNA emitter exhibits a high external quantum efficiency of 7.8% as a blue fluorescent emitter. The lifetime of the boron derived emitters was much longer than a blue emitter derived from pyrene. This work demonstrated the effectiveness of the boron derived emitters as deep blue fluorescent emitters.

The Blue Problem: OLED Stability and Degradation Mechanisms

“…The role of the host was assigned to α-ADN (Figure a), which has a high singlet energy, needed for exciton transfer to the blue MR-TADF terminal emitter, and a low-lying triplet level, suitable for triplet exciton quenching. The devices with DABNA-1 and t-DABNA showed deep blue emission at CIE coordinates of (0.126, 0.098) and (0.135, 0.072), respectively; however, the EQE max for the devices with 5 wt % emitter concentration in the host was only 5.5 and 7.8%, while the LT95 values were 2.7 and 10.0 h (when renormalized to an initial luminance of 1000 cd/m 2 ), respectively . 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.…”

“…One potential solution would be to replace the blue OLEDs with ones employing TADF emitters, so long as these The importance of developing both efficient and long-lasting devices becomes evident when surveying literature performance metrics for blue OLEDs, where a large array of compounds were investigated as emitters (Figure 2) and hosts (Figure 3). While some still assert that blue OLEDs based on fluorescent molecules are the only ones capable of reaching reasonable lifetimes, 59 recent progress to improve their efficiency to match that of red and green devices has hit a ceiling in term of their EQE max . There have been consistent efforts at producing stable OLEDs that operate by only harvesting singlet excitons for emission, but despite significant improvements in device lifetime, the EQE max was at best half of what could be achieved with phosphorescent or TADF emitters.…”

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

“…The devices with DABNA-1 and t-DABNA showed deep blue emission at CIE coordinates of (0.126, 0.098) and (0.135, 0.072), respectively; however, the EQE max for the devices with 5 wt % emitter concentration in the host was only 5.5 and 7.8%, while the LT95 values were 2.7 and 10.0 h (when renormalized to an initial luminance of 1000 cd/m 2 ), respectively. 59 In another study, a donor–acceptor material based on pyrene Py(5,9)BDPA ( Figure 2 b) was used with α,β-ADN ( Figure 3 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%.…”