Donor Extended Blue TADF Dendrimer for High-Performance Solution-Processed OLEDs.

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Efficient and stable blue organic light-emitting diodes (OLEDs) fabricated via solution processing are crucial for next-generation displays but remain a significant challenge.
• Existing Thermally Activated Delayed Fluorescence (TADF) emitters often face limitations in solubility and charge transport, hindering their performance in solution-processed devices.

Purpose of the Study:

• To introduce a rational donor decoration strategy for enhancing TADF emitters for blue solution-processed OLEDs.
• To improve the solubility and hole-transport properties of TADF emitters without sacrificing blue emission characteristics.

Main Methods:

• Synthesized a novel TADF emitter, DOBNA-SpAc-DCz, by introducing ter(tert-butylcarbazole) units onto the DOBNA-SpAc core.
• Characterized the photophysical properties, including photoluminescence quantum yield (Φ_PL) and singlet-triplet energy gap (ΔE_ST).
• Fabricated and tested solution-processed OLED devices using the synthesized emitter, evaluating external quantum efficiency (EQE) and color coordinates.

Main Results:

• DOBNA-SpAc-DCz exhibited a high Φ_PL of 93% and a small ΔE_ST of 0.01 eV, enabling fast reverse intersystem crossing (k_RISC > 1 × 10⁶ s^-1) and a short delayed lifetime of 2 µs.
• Solution-processed OLEDs achieved a maximum EQE_max of 29.4 ± 0.1% with CIE coordinates of (0.145, 0.211).
• Carbazole substituents improved hole transport and distributed the recombination zone, while faster k_RISC suppressed triplet-related annihilation.

Conclusions:

• Peripheral donor dendron decoration of spiroacridine-based TADF emitters is an effective strategy for achieving high-efficiency emitters.
• The developed DOBNA-SpAc-DCz emitter is suitable for high-performance, solution-processed blue OLED applications.
• This approach offers a pathway to overcome key challenges in blue OLED technology.