Dataset Information

Asymmetrical-Dendronized TADF Emitters for Efficient Non-doped Solution-Processed OLEDs by Eliminating Degenerate Excited States and Creating Solely Thermal Equilibrium Routes.

ABSTRACT: The mechanism of thermally activated delayed fluorescence (TADF) in dendrimers is not clear. We report that fully-conjugated or fully-nonconjugated structures cause unwanted degenerate excited states due to multiple identical dendrons, which limit their TADF efficiency. We have synthesized asymmetrical "half-dendronized" and "half-dendronized-half-encapsulated" emitters. By eliminating degenerate excited states, the triplet locally excited state is ≥0.3 eV above the lowest triplet charge-transfer state, assuring a solely thermal equilibrium route for an effective spin-flip process. The isolated encapsulating tricarbazole unit can protect the TADF unit, reducing nonradiative decay and enhancing TADF performance. Non-doped solution-processed devices reach a high external quantum efficiency (EQE_max ) of 24.0 % (65.9 cd A^-1 , 59.2 lm W^-1 ) with CIE coordinates of (0.24, 0.45) with a low efficiency roll-off and EQEs of 23.6 % and 21.3 % at 100 and 500 cd m^-2 .

SUBMITTER: Li C

PROVIDER: S-EPMC9306820 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Asymmetrical-Dendronized TADF Emitters for Efficient Non-doped Solution-Processed OLEDs by Eliminating Degenerate Excited States and Creating Solely Thermal Equilibrium Routes.

Li Chensen C Harrison Alastair K AK Liu Yuchao Y Zhao Zhennan Z Zeng Cheng C Dias Fernando B FB Ren Zhongjie Z Yan Shouke S Bryce Martin R MR

Angewandte Chemie (International ed. in English) 20220120 19

The mechanism of thermally activated delayed fluorescence (TADF) in dendrimers is not clear. We report that fully-conjugated or fully-nonconjugated structures cause unwanted degenerate excited states due to multiple identical dendrons, which limit their TADF efficiency. We have synthesized asymmetrical "half-dendronized" and "half-dendronized-half-encapsulated" emitters. By eliminating degenerate excited states, the triplet locally excited state is ≥0.3 eV above the lowest triplet charge-transfe ...[more]

PMID: 34870886

Similar Datasets

Project description:Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials of polycyclic heteroaromatics are attractive narrowband emitters in wide-color-gamut organic light-emitting diodes (OLEDs). However, deep-blue MR-TADF emitters with CIE coordinates fulfilling the BT.2020 standard and high efficiency still remain a significant challenge. Herein, two novel emitters NBO-mSAF and NBO-pSAF were developed by incorporating an electron donor, 10H-spiro[acridine-9,9'-fluorene] (SAF), at the para-position of the oxygen atom and the para-position of the boron atom in the nitrogen/boron/oxygen (N/B/O) ternary doped asymmetric MR skeleton. With appropriate electron-donating capacity and rigid spiro-structure, SAF was selected as the donor so that the long-range charge transfer triplet state (3LRCT) is induced to accelerate the reverse intersystem crossing (RISC) process, while the 1LRCT aligns higher than the short-range CT state (1SRCT) of the N/B/O core to retain the MR characters. As a result, these optimized emitters exhibit deep-blue TADF with narrow spectra and a high RISC rate constant of 3.4 × 105 s-1. In hyperfluorescence OLEDs with a TADF emitter DMAC-DPS as the sensitizer and PPF as the host, NBO-mSAF and NBO-pSAF achieved maximum external quantum efficiencies (EQEmax) of 26.7% and 25.2%. Interestingly, improved performance was realized in a traditional device configuration with a single bipolar host 26DCzPPy but without any sensitizer, where NBO-mSAF realized a higher EQEmax of 29.5% and CIE (0.128, 0.114), and NBO-pSAF exhibited an EQEmax of 20.5% and CIE of (0.147, 0.048). Narrow full width at half maximum (FWHM) values of 26-28 nm were achieved in both devices. Among all the deep-blue N/B/O type MR-TADF emitters with CIEx ≤ 0.15 and CIEy ≤ 0.12 ever reported so far, NBO-mSAF exhibited a highest EQEmax of 29.5%, which is even higher than those obtained with sensitizers, while the CIEy = 0.048 of the NBO-pSAF device is close to the standard blue (0.046) according to BT.2020, with a decent EQE of 20%.

Dataset Information

Asymmetrical-Dendronized TADF Emitters for Efficient Non-doped Solution-Processed OLEDs by Eliminating Degenerate Excited States and Creating Solely Thermal Equilibrium Routes.

Publications

Asymmetrical-Dendronized TADF Emitters for Efficient Non-doped Solution-Processed OLEDs by Eliminating Degenerate Excited States and Creating Solely Thermal Equilibrium Routes.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets