Highly Efficient Green and Red Narrowband Emissive Organic Light‐Emitting Diodes Employing Multi‐Resonant Thermally Activated Delayed Fluorescence Emitters**

Abstract

Herein, we demonstrate how judicious selection of the donor decorating a central multi-resonant thermally activated delayed fluorescence (MR-TADF) core based on DiKTa can lead to very high-performance OLEDs. By decorating the DiKTa core with triphenylamine (TPA) and diphenylamine (DPA), 3TPA-DiKTa and 3DPA-DiKTa exhibit bright, narrowband green and red emission in doped films, respectively. The OLEDs based on these emitters showed record-high performance for this family of emitters with maximum external quantum efficiencies (EQE max ) of 30.8 % for 3TPA-DiKTa at λ EL of 551 nm and 16.7 % for 3DPA-DiKTa at λ EL = 613 nm. The efficiency roll-off in the OLEDs was improved significantly by using 4CzIPN as an assistant dopant in hyperfluorescence (HF) devices. The outstanding device performance has been attributed to preferential horizontal orientation of the transition dipole moments of 3TPA-DiKTa and 3DPA-DiKTa.

Efficient, narrow-band, and stable electroluminescence from organoboron-nitrogen-carbonyl emitter

“…However, their device performances were less ideal, showing broader spectral bands and poor e ciencies with serious e ciency roll-offs. [24][25][26][27][28][29][30][31][32][33] In short, our calculation results have thus demonstrated that the newly proposed h-BNCO strategy not only reduces ΔE S1T1 and ΔE T2T1 but also increases the SOC values, eventually substantially accelerating the RISC process.…”

Recent progress and prospects of fluorescent materials based on narrow emission

“…14i), which contain three diphenylamine or triphenylamine donor groups and modify a central MR-TADF core ( DiKTa ). 111 In 2 wt% doped mCP films, 3TPA-DiKTa shows a green emission at λ PL of 551 nm with an FWHM of 58 nm and a PLQY of 93%, while 3DPA-DiKTa exhibits red emission at λ PL of 617 nm with an FWHM of 56 nm and a PLQY of 60%. Compared to 3TPA-DiKTa with a Δ E ST of 0.13 eV, a τ d of 131 μs and a k RISC of 2.49 × 10 4 s −1 , 3DPA-DiKTa has a larger Δ E ST of 0.20 eV, a longer τ d of 323 μs and a k RISC of 0.14 × 10 4 s −1 .…”

“…14 (a-j) Chemical structures of emitters discussed in Section 3.2.3. [103][104][105][106][107][108][109][110][111]113 (EQE max = 6.1%). The PhDMAC-BN-based OELD exhibited an EQE max of 27.2%, a l EL of 480 nm, an FWHM of 34 nm, and CIE color coordinates of (0.105, 0.264), and the EQE max was further improved to 33.9% when 3tPAB was employed as a sensitizer for PhDMAC-BN.…”

Carbonyl (CO)/N-based thermally activated delayed fluorescent materials with high efficiency and fast reverse intersystem crossing rate: a theoretical design and study

“…[1][2][3][4][5][6][7] The feature of TADF is the efficient conversion from the triplet-excited state to the singlet state by the reverse intersystem crossing (RISC) process and can achieve a theoretical internal quantum efficiency (IQE) of 100%. 2,[8][9][10][11] In principle, a small energy gap DE ST between the lowest singlet excited state S 1 and the lowest triplet excited state T 1 is crucial to achieving fast RISC rates and low efficiency roll-off. [12][13][14] By designing highly twisted electron donor (D)electron acceptor (A) molecular configurations, DE ST can be reduced with effective separation between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).…”