Triptycene‐Fused Sterically Shielded Multi‐Resonance TADF Emitter Enables High‐Efficiency Deep Blue OLEDs with Reduced Dexter Energy Transfer

Abstract

Designing multi-resonance (MR) emitters that can simultaneously achieve narrowband emission and suppressed intermolecular interactions is challenging for realizing high color purity and stable blue organic lightemitting diodes (OLEDs). Herein, a sterically shielded yet extremely rigid emitter based on a triptycene-fused B,N core (Tp-DABNA) is proposed to address the issue. Tp-DABNA exhibits intense deep blue emissions with a narrow full width at half maximum (FWHM) and a high horizontal transition dipole ratio, superior to the wellknown bulky emitter, t-DABNA. The rigid MR skeleton of Tp-DABNA suppresses structural relaxation in the excited state, with reduced contributions from the medium-and high-frequency vibrational modes to spectral broadening. The hyperfluorescence (HF) film composed of a sensitizer and Tp-DABNA shows reduced Dexter energy transfer compared to those of t-DABNA and DABNA-1. Notably, deep blue TADF-OLEDs with the Tp-DABNA emitter display higher external quantum efficiencies (EQE max = 24.8 %) and narrower FWHMs (� 26 nm) than t-DABNA-based OLEDs (EQE max = 19.8 %). The HF-OLEDs based on the Tp-DABNA emitter further demonstrate improved performance with an EQE max of 28.7 % and mitigated efficiency roll-offs.

High efficiency and high color purity deep‐blue organic light‐emitting diodes with blue index >500

“…Device C1 exhibits CIEy coordination of 0.097, which are almost identical to the EL performance of Device A1, implying efficient transfer from PBD to FBD1. 16 In addition, the EQE of Device C1 has shown remarkable increased over two times compared with Device B. In comparison to nonsensitized devices, Device C1 achieved a higher EQE, current efficiency, and BI, suggesting its superior exciton utilization and efficient energy transfer.…”

“…[13][14][15] Besides, favorable terminal fluorescent emitter is required with narrow FWHM for outstanding color purity. 16 In our study, a deep-blue phosphorescent material was involved as sensitizer for narrow FWHM blue fluorescent emitter. Sufficient FRET process occurred by large spectral overlap between the absorption spectra of the terminal fluorescent emitter and the photoluminescence (PL) spectra of the sensitizer.…”

“…Apparently, fast FRET process can effectively reduce triplet exciton concentration, suppress triplet exciton annihilations, alleviate efficiency roll‐off at high brightness, and ensure a high efficiency for sensitized OLEDs 13–15 . Besides, favorable terminal fluorescent emitter is required with narrow FWHM for outstanding color purity 16 …”

Systematic Study to Choose Appropriate Materials Combination for Green Hyperfluorescent Organic Light-Emitting Diodes

“…Lately, thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs) have drawn attention in both academia and industry due to their high efficiency and low cost as they can boost the device performance with absolute exciton utilization. − The TADF emitters can undergo efficient up-conversion through a fast reverse intersystem crossing (RISC) process owing to minimal energy gap between the lowest excited singlet and triplet states (Δ E ST ), where all singlet and triplet excitons can be harvested for light emission. − Despite these advantages, the main challenge with TADF emitters is their long exciton lifetime, invoking poor device stability and suffering severe efficiency roll-off at high current density . In addition, the intramolecular charge transfer characteristics of the emitters offer a broad spectrum, hence low color purity. , …”

Unraveling Degradation Processes and Strategies for Enhancing Reliability in Organic Light-Emitting Diodes

“…Organic light-emitting diodes (OLEDs) are poised to become the leading technology in high-quality flat-panel display [1] and solid-state lighting. Their disruptive features, including energy efficiency [2], wide viewing angles, fast response times, high contrast, and exceptional color purity (Figure 1a), make them ideal candidates for various applications (a few of them are shown in Figure 1b). In contrast, traditional LEDs require complex processing to achieve comparable light quality, and achieving uniform dispersion into a near-plane light source remains a challenge for them.…”