A Series of Fused Carbazole/Carbonyl Based Blue to Yellow‐Green Thermally Activated Delayed Fluorescence Materials for Efficient Organic Light‐Emitting Diodes. Issue 21 (26th August 2021)

• Record Type: Journal Article
• Authors: Luo, Xu‐Feng; Li, Fang‐Ling; Zou, Jian‐Wei; Zou, Qian; Su, Jian; Mao, Meng‐Xi; Zheng, You‐Xuan
• Is Part Of: Advanced optical materials. Volume 9:Issue 21(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-26
• Subjects: carbazole -- carbonyl -- high‐efficiency -- organic light‐emitting diodes -- thermally activated delayed fluorescence; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202100784
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: The exploitation of novel fused carbazole/carbonyl emitters is essential to broaden the application of thermally activated delayed fluorescence (TADF) materials for organic light‐emitting diodes (OLEDs). Here, with the aid of the addition and cyclization of the cyano group with the ortho‐carbazole, fused carbazole/carbonyl based TADF emitters are effectively synthesized via this new synthetic strategy. The attachment of ancillary donors including carbazole, diphenylamine, and phenolazine to the fused carbazole/carbonyl skeletons further tunes their emissions from blue to yellow‐green. Particularly, pure‐blue OLEDs incorporating the peripheral carbazole attached emitter exhibit a maximum external quantum efficiency (EQEmax ) of 22.3%, with a small full width at half maximum (FWHM) of 48 nm. In addition, the peripheral phenolazine attached yellow‐green emitter shows extremely small singlet−triplet state energy gap (Δ E ST ) of 0.01 eV, high photoluminescence quantum efficiency of 82.5%, short delayed fluorescence lifetime of 6.2 µs and good OLED performances with an EQEmax of 21.7%, an FWHM of 68 nm and low efficiency roll‐off. These results demonstrate that the new synthetic strategy for fused carbazole/carbonyl molecules provide a valuable reference for the design of high‐efficient TADF emitters. Abstract : Five carbazole/carbonyl‐based thermally activated delayed fluorescence emitters are synthesized via the addition and cyclization of cyano group with ortho‐carbazole. Photoelectric properties can be effectively mediated through changing the substitution positions and peripheral donors. Three organic light‐emitting diodes achieve the external quantum efficiencies of 22.3, 21.2, and 21.7% with full widths at half maximum of 48, 66, and 68 nm, respectively.