Design of highly efficient deep-blue organic afterglow through guest sensitization and matrices rigidification

Shen Xu,Shuang Wang,Chao Zheng,Hui Li,Jingyu Zhang,Guichuan Xing,Runfeng Chen,Chunyuan Song,Wei Huang,Wu Wang

doi:10.1038/s41467-020-18572-9

Abstract

Blue/deep-blue emission is crucial for organic optoelectronics but remains a formidable challenge in organic afterglow due to the difficulties in populating and stabilizing the high-energy triplet excited states. Here, a facile strategy to realize the efficient deep-blue organic afterglow is proposed via host molecules to sensitize the triplet exciton population of guest and water implement to suppress the non-radiative decays by matrices rigidification. A series of highly luminescent deep-blue (405–428 nm) organic afterglow materials with lifetimes up to 1.67 s and quantum yields of 46.1% are developed. With these high-performance water-responsive materials, lifetime-encrypted rewritable paper has been constructed for water-jet printing of high-resolution anti-counterfeiting patterns that can retain for a long time (>1 month) and be erased by dimethyl sulfoxide vapor in 15 min with high reversibility for many write/erase cycles. These results provide a foundation for the design of high-efficient blue/deep-blue organic afterglow and stimuli-responsive materials with remarkable applications.

Highlights

Blue/deep-blue emission is crucial for organic optoelectronics but remains a formidable challenge in organic afterglow due to the difficulties in populating and stabilizing the highenergy triplet excited states
The deep-blue Organic ultralong room temperature phosphorescence (OURTP) materials were prepared by using cyanuric acid (CA) as a universal host owing to its abundant interaction positions that can efficiently suppress the luminescence quenching effects and non-radiative decay processes, and phthalic acid derivatives as the guest molecules because they can interact effectively with CA for single molecular dispersion and suppressed non-radiative vibration through H-bonding (Fig. 1a)[24,25]
Trimesic acid (TMA) with three carboxyl moieties which can facilitate the n–π* transition, spin–orbit coupling, and molecular interactions with CA is chosen as the guest molecule (Supplementary Fig. 1)

Summary

Results

After being doped into CA at a low concentration of 5 wt‰ via ultrasonicating aqueous mixture of TMA and CA at room temperature (Fig. 1b), the as-prepared powder of CT5-0 after removing the solvent under vacuum at 40 °C for 24 h exhibits long phosphorescent lifetime of 1.13 s and PhQY of 9.3% under ambient conditions (Fig. 1c) This efficient OURTP is deep blue (406 nm), which is very different to its intrinsic green emission. TMA shows a decent phosphorescence band around 400 nm even at single molecular state in ethanol, while the steady-state photoluminescence (PL) spectrum of CA is dominated by the blue phosphorescence Both CA and TMA are capable of populating T1 upon photoexcitation for blue phosphorescence with weak brightness, low quantum efficiencies, and short lifetimes (Supplementary Table 2).

H OO OHH

78 K 158 K 198 K 238 K 258 K 278 K

Discussion

Methods