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. 2020 Jun 14;7(15):2000804.
doi: 10.1002/advs.202000804. eCollection 2020 Aug.

Axially Chiral Biphenyl Compound-Based Thermally Activated Delayed Fluorescent Materials for High-Performance Circularly Polarized Organic Light-Emitting Diodes

Zhen-Long Tu  1 , Zhi-Ping Yan  1 , Xiao Liang  1 , Lei Chen  1 , Zheng-Guang Wu  1 , Yi Wang  1 , You-Xuan Zheng  1 , Jing-Lin Zuo  1 , Yi Pan  1
Affiliations

Axially Chiral Biphenyl Compound-Based Thermally Activated Delayed Fluorescent Materials for High-Performance Circularly Polarized Organic Light-Emitting Diodes

Zhen-Long Tu et al. Adv Sci (Weinh). .

Abstract

To boost intrinsic circularly polarized luminescence (CPL) properties of chiral emitters, an axially chiral biphenyl unit is inlaid in thermally activated delayed fluorescent (TADF) skeleton, urging the participation of chiral source in frontier molecular orbital distributions. A pair of enantiomers, (R)-BPPOACZ and (S)-BPPOACZ, containing the cyano as electron-withdrawing moieties and carbazole and phenoxazine as electron-donating units are synthesized and separated. The circularly polarized TADF enantiomers exhibit both high photoluminescence quantum yield of 86.10% and excellent CPL activities with maximum dissymmetry factor |g PL| values of almost 10-2 in solution and 1.8 × 10-2 in doped film, which are among the best values of previously reported small chiral organic materials. Moreover, the circularly polarized organic light-emitting diodes based on the TADF enantiomers achieve the maximum external quantum efficiency of 16.6% with extremely low efficiency roll-off. Obvious circularly polarized electroluminescence signals with |g EL| values of 4 × 10-3 are also recorded.

Keywords: axially chiral biphenyl compound; circularly polarized electroluminescence; circularly polarized luminescence; organic light‐emitting diodes; thermally activated delayed fluorescence.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
a) Molecular design and chemical structures of the TADF enantiomers (S)‐BPPOACZ and (R)‐BPPOACZ. b) Single crystal of (R)‐BPPOACZ. c) HOMO and LUMO distributions of (R)‐BPPOACZ.
Figure 2
Figure 2
a) Absorption and fluorescence spectra of (rac)‐BPPOACZ in toluene (5.0 × 10−5 m), and fluorescence spectra of doped film ((rac)‐BPPOACZ:26DCzPPy = 2:10) at room temperature. b) ECD spectra of (R/S)‐BPPOACZ in toluene (5.0 × 10−5 m). c) CPL spectra of (R/S)‐BPPOACZ in toluene (5.0 × 10−5 m). d) g PL versus wavelength curves of (R/S)‐BPPOACZ in toluene. e) CPL spectra in doped film ((R/S)‐BPPOACZ:26DCzPPy = 2:10). f) g PL versus wavelength curves in doped film ((R/S)‐BPPOACZ:26DCzPPy = 2:10).
Figure 3
Figure 3
Device D‐RAC performances: a) EL spectrum, b) current density–luminance–voltage curves, c) EQE–luminance curves, and d) current‐efficiency/power‐efficiency–luminance curves.
Figure 4
Figure 4
a) CPEL spectra of devices D‐R and D‐S. b) g EL curves of devices D‐R and D‐S.
See this image and copyright information in PMC

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