Multiple‐Resonance‐Type TADF Emitter as Sensitizer Improving the Performance of Blue Fluorescent Organic Light‐Emitting Diodes

Abstract

Due to the limitation of donor and acceptor group selection, the efficient thermally activated delayed fluorescence (TADF) type sensitizer used for blue organic light‐emitting diodes (OLEDs) is rare. Multiple resonance (MR) type TADF emitters can easily achieve efficient blue emission. And the compounds exhibit small Stokes shift and lower absorption energy under the same emission color compared with traditional TADF, mitigating the damage of high‐energy absorption of sensitizer on material stability. However, their characteristics as sensitizers have not been explored. In this work, a deep‐blue MR‐TADF compound (3tPAB) is selected as a sensitizer for both blue traditional fluorescence and MR‐TADF OLED. Given the improved photoluminescence quantum yield and the utilization of triplet excitons, the TADF‐sensitized fluorescent device using 3tPAB as sensitizer presents a maximum external quantum efficiency (EQEmax) of 14.4%, showing ≈2.4 times increase compared with the device without sensitizer. More impressively, TADF‐sensitized TADF (TST) device using 3tPAB as sensitizer and MR‐TADF compound PhDMAC‐BN as emitter exhibits EQEmax of 33.9%. And in TST device, efficient Förster energy transfer is demonstrated, thus, the device can maintain high color purity. The work first demonstrates the feasibility of MR‐TADF as a sensitizer and provides a new strategy for developing high‐performance blue OLED with high color purity.

Triphenylamine‐Functionalized Multiple‐Resonance TADF Emitters with Accelerated Reverse Intersystem Crossing and Aggregation‐Induced Emission Enhancement for Narrowband OLEDs

“…In specific, the BNCz-pTPA-based device exhibited a maximum EQE of 27.3% without utilizing using any TADF-sensitizing host for efficient triplet-to-singlet conversion. [20,[60][61][62] This study offers a facile tactic for designing MR-TADF emitters with ACQ suppression and RISC enhancement simultaneously for efficient high-color-purity OLEDs.…”

Synthetic progress of organic thermally activated delayed fluorescence emitters via C–H activation and functionalization

“…Given its deep-blue emission, weak concentration dependence, highly radiative process, and potentially suppressed Dexter energy transfer, t -DAB-DPA was further used as a sensitizer for the improvement of blue TADF-sensitized fluorescent (TSF) and TADF-sensitized TADF (TST) OLEDs. 239 These works signify an efficient quenching-resistant molecular synthesis and design strategy for high-performance B/N-based MR-TADF emitters through BBr 3 -mediated C−H borylation.…”

Recent progress and prospects of fluorescent materials based on narrow emission

“…14j). 113 3tPAB was chosen as a sensitizer for two reasons: one is a large spectral overlap between the PL spectra of the sensitizer and the absorption of the emitter, and the other is the introduction of tert-butyl in the sensitizer prepared using DtPaPy as an emitter, which further induced the occurrence of Fo ¨rster energy transfer (FET) and effectively inhibited the Dexter energy transfer (DET). First, the corresponding nonsensitized OLEDs were prepared using DtPaPy as an emitter, and TADF-sensitized fluorescence (TSF) OLEDs were prepared using DtPaPy as an emitter and 3tPAB as a sensitizer.…”

“…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.…”