Toward a BT.2020 green emitter through a combined multiple resonance effect and multi-lock strategy

Abstract

Color-saturated green-emitting molecules with high Commission Internationale de L’Eclairage (CIE) y values have great potential applications for displays and imaging. Here, we linked the outer phenyl groups in multiple-resonance (MR)-type blue-emitting B (boron)-N (nitrogen) molecules through bonding and spiro-carbon bridges, resulting in rigid green emitters with thermally activated delayed fluorescence. The MR effect and multiple interlocking strategy greatly suppressed the high-frequency vibrations in the molecules, which emit green light with a full-width at half-maximum of 14 nm and a CIE y value of 0.77 in cyclohexane. These were the purest green molecules with quantum efficiency and color purity that were comparable with current best quantum dots. Doping these emitters into a traditional green-emitting phosphorescence organic light-emitting diode (OLED) endowed the device with a Broadcast Service Television 2020 color-gamut, 50% improved external quantum efficiency, and an extremely high luminescence of 5.1 × 105 cd/m2, making it the greenest and brightest OLED ever reported.

Multiple Fusion Strategy for High‐Performance Yellow OLEDs with Full Width at Half Maximums Down to 23 nm and External Quantum Efficiencies up to 37.4%

“…The remarkably longer TADF lifetimes (compared to traditional charge transfer (CT)‐type TADF emitters with similar Δ E ST values) can be ascribed to the small recombination energy of these MR molecules according to the Marcus–Levich–Jortner theory (Figure S6, Supporting Information). [ 10 ] The temperature‐dependent transient PL decay of the 3 wt% doped films was also performed, further verifying the TADF nature of BN‐DICz and DBN‐ICz (Figure S7, Supporting Information).…”

Metal‐Perturbed Multiresonance TADF Emitter Enables High‐Efficiency and Ultralow Efficiency Roll‐Off Nonsensitized OLEDs with Pure Green Gamut

“…To the best of our knowledge, the EQE max and the value at 10 000 cd m −2 (Figure 4f; Table S5, Supporting Information), together with the maximum brightness for DCzBN–Au, represent the state‐of‐the‐art performance for BN MR‐TADF OLEDs, including those using iridium(III) sensitizers. [ 34 ] It is necessary to point out that ten devices based on DCzBN–Au have been fabricated to verify the reproducible performances. Average values of 34.7% and 31.4% were obtained for EQE max and EQE at 10 000 cd m −2 , respectively (Figure S6, Supporting Information).…”

Highly Efficient and Stable Blue OLEDs Based on B—N Bonds Embedded 6,12‐Diphenyl‐5,11‐dihydroindolo[3,2‐b]carbazole with Narrowband Emission and Extended Lifetime†

“…This pioneering work paves a new way for the development of narrowband emitters with high color purities, and a wide variety of B,X‐doped MR emitters (X = N, O, S, and Se) covering the full‐color spectra range from blue to red/deep‐red have been extensively developed toward OLED display applications. [ 23‐28 ] However, those B,N‐doped MR emitters always suffer from tedious synthesis processes with low yields and dangerous lithium reagents. [ 25 ] In addition, narrowband blue emitters with high color purity and high stability are still relatively rare among the large number of B,N‐doped MR emitters reported previously.…”