Near-Infrared-Excitable Organic Ultralong Phosphorescence through Multiphoton Absorption.

Ye Tao,Huanhuan Li,Qingqing Yang,Lele Tang,Wei Huang,Ping Li,Wenbo Hu,Jibiao Jin,Guichuan Xing,Runfeng Chen,Chao Zheng,Qi Wei,Quli Fan

doi:10.34133/2020/2904928

Abstract

Organic ultralong room-temperature phosphorescence (OURTP) with a long-lived triplet excited state up to several seconds has triggered widespread research interests, but most OURTP materials are excited by only ultraviolet (UV) or blue light owing to their unique stabilized triplet- and solid-state emission feature. Here, we demonstrate that near-infrared- (NIR-) excitable OURTP molecules can be rationally designed by implanting intra/intermolecular charge transfer (CT) characteristics into H-aggregation to stimulate the efficient nonlinear multiphoton absorption (MPA). The resultant upconverted MPA-OURTP show ultralong lifetimes over 0.42 s and a phosphorescence quantum yield of ~37% under both UV and NIR light irradiation. Empowered by the extraordinary MPA-OURTP, novel applications including two-photon bioimaging, visual laser power detection and excitation, and lifetime multiplexing encryption devices were successfully realized. These discoveries illustrate not only a delicate design map for the construction of NIR-excitable OURTP materials but also insightful guidance for exploring OURTP-based nonlinear optoelectronic properties and applications.

Highlights

Long-lived organic phosphorescence with lifetime over 0.1 s has shown great significance in both scientific understandings and technological applications ranging from anticounterfeiting [1,2,3], persistent light-emitting diodes [4], bioimaging [5, 6], and temperature sensing [7] to logic computing [8]
organic ultralong room-temperature phosphorescence (OURTP) can only be excited by ultraviolet (UV) or blue light [24,25,26], owing to the intrinsic multiple exciton transformation features of OURTP (Figure 1(a)), where the photoexcited excitons on the lowest singlet excited state (S1) should be transformed to the triplet exciton through intersystem crossing (ISC) on the high-lying triplet excited state (Tn) firstly, followed by internal conversion (IC) and triplet stabilization processes to form the stabilized Tn (Tn∗) [24]
We choose the strong electron-withdrawing difluoroboron β-diketonate (BF2bdk) as the central acceptor moiety and two π-conjugation arylamines of carbazole and diamine as donor units. This design can motivate efficient intramolecular CT (ICT) and space CT (SCT) between arylamines and BF2bdk to boost multiphoton absorption (MPA) in both single molecular and aggregated states [36, 37] and facilitate ISC by the inherent nonbonding p electrons of boron (B) and lone pair electrons of nitrogen (N) and fluorine (F) [24, 38]; various interlocked interactions empowered by the multiple heteroatom incorporation (Figures 1(b) and 1(c)) result in the greatly suppressed nonradiative decay of the excited states for high luminescent efficiency; the implanted planar π-conjugation arylamine endows the construction of H-aggregation, which is crucial in the stabilization of triplet excitons for OURTP

Summary

Introduction

Long-lived organic phosphorescence with lifetime over 0.1 s has shown great significance in both scientific understandings and technological applications ranging from anticounterfeiting [1,2,3], persistent light-emitting diodes [4], bioimaging [5, 6], and temperature sensing [7] to logic computing [8]. We choose the strong electron-withdrawing difluoroboron β-diketonate (BF2bdk) as the central acceptor moiety and two π-conjugation arylamines of carbazole and diamine as donor units This design can motivate efficient ICT and SCT between arylamines and BF2bdk to boost MPA in both single molecular and aggregated states [36, 37] and facilitate ISC by the inherent nonbonding p electrons of boron (B) and lone pair electrons of nitrogen (N) and fluorine (F) [24, 38]; various interlocked interactions empowered by the multiple heteroatom incorporation (Figures 1(b) and 1(c)) result in the greatly suppressed nonradiative decay of the excited states for high luminescent efficiency; the implanted planar π-conjugation arylamine endows the construction of H-aggregation, which is crucial in the stabilization of triplet excitons for OURTP

Results

Discussion

Materials and Methods

Conflicts of Interest