Room-temperature Phosphorescence Materials Research Articles

Excellent Persistent Near-Infrared Room Temperature Phosphorescence from Highly Efficient Host-Guest Systems.

Organic near-infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal-to-background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy-gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten-folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host-guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs.

Stretchable phosphorescent polymers by multiphase engineering

Stretchable phosphorescence materials potentially enable applications in diverse advanced fields in wearable electronics. However, achieving room-temperature phosphorescence materials simultaneously featuring long-lived emission and good stretchability is challenging because it is hard to balance the rigidity and flexibility in the same polymer. Here we present a multiphase engineering for obtaining stretchable phosphorescent materials by combining stiffness and softness simultaneously in well-designed block copolymers. Due to the microphase separation, copolymers demonstrate an intrinsic stretchability of 712%, maintaining an ultralong phosphorescence lifetime of up to 981.11 ms. This multiphase engineering is generally applicable to a series of binary and ternary initiator systems with color-tunable phosphorescence in the visible range. Moreover, these copolymers enable multi-level volumetric data encryption and stretchable afterglow display. This work provides a fundamental understanding of the nanostructures and material properties for designing stretchable materials and extends the potential of phosphorescence polymers.

Stimulus-responsive room temperature phosphorescent materials based on poly(vinylalcohol) with tunable multicolor afterglow

Stimulus-responsive room temperature phosphorescent materials based on poly(vinylalcohol) with tunable multicolor afterglow

Fully Exploiting Clusterization‐Triggered Room Temperature Phosphorescence of Cellulose by Stepwise Rigidification for Long‐Lived and Excitation Wavelength‐Dependent Afterglows

AbstractAchieving long‐lived room temperature phosphorescence (RTP) in nonconventional luminophores devoid of any conjugated units is fascinating but remains formidably challenging due to their low intersystem crossing efficiency and strong nonradiative decay. Herein, a stepwise rigidification strategy is developed to suppress the nonradiative decay and fully exploit the clusterization‐triggered RTP performance of cellulose. Specifically, the crystallinity is enhanced, and hydrogen bonding is reconstructed by a directed oxidation‐reduction reaction to afford a more rigid environment of cellulose; then, the reconstructed cellulose is further cross‐linked by boric acid to activate double confinement architecture. In return, the phosphorescence lifetime of the target cellulose increases almost one order of magnitude, and the phosphorescence quantum yield increases more than 27 folds. Moreover, the afterglow of the RTP cellulose can be regulated from blue to green by changing excitation wavelength, which is useful for advanced information encryption and anti‐counterfeiting. The stepwise rigidification strategy is also applicable for preparing other nature polysaccharides‐based long‐lived RTP materials, such as chitosan and sodium alginate. Nature polysaccharides are completely biodegradable; thus, this work paves the way for the development of eco‐friendly and practical color‐variable RTP materials.

Finely manipulating room temperature phosphorescence by dynamic lanthanide coordination toward multi-level information security

Room temperature phosphorescence materials have garnered significant attention due to their unique optical properties and promising applications. However, it remains a great challenge to finely manipulate phosphorescent properties to achieve desirable phosphorescent performance on demand. Here, we show a feasible strategy to finely manipulate organic phosphorescent performance by introducing dynamic lanthanide coordination. The organic phosphors of terpyridine phenylboronic acids possessing excellent coordination ability are covalently embedded into a polyvinyl alcohol matrix, leading to ultralong organic room temperature phosphorescence with a lifetime of up to 0.629 s. Notably, such phosphorescent performance, including intensity and lifetime, can be well controlled by varying the lanthanide dopant. Relying on the excellent modulable performance of these lanthanide-manipulated phosphorescence films, multi-level information encryption including attacker-misleading and spatial-time-resolved applications is successfully demonstrated with greatly improved security level. This work opens an avenue for finely manipulating phosphorescent properties to meet versatile uses in optical applications.

Circularly Polarized Room Temperature Phosphorescence through Twisting-induced Helical Structures from Polyvinyl Alcohol-based Fibers Containing Hydrogen-bonded Dyes.

Room temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting-induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q-NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6%, and the improved tensile strength being 1.7 times than pure PVA fiber (172 ± 5.82 vs 100 ± 5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP-RTP) is readily achieved by imparting left- or right-hand helical structure through simply twisting, enabling large-scale production of chiral Q-NH2@PVA fiber with dissymmetry factor of 10-2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA-based fibers with outstanding adaptivity in cutting-edge anti-counterfeiting technology.

Circularly Polarized Room Temperature Phosphorescence through Twisting‐induced Helical Structures from Polyvinyl Alcohol‐based Fibers Containing Hydrogen‐bonded Dyes

Room temperature phosphorescence (RTP) materials have garnered significant attention owing to its distinctive optical characteristics and broad range of potential applications. However, the challenge remains in producing RTP materials with more simplicity, versatility, and practicality on a large scale, particularly in achieving chiral signals within a single system. Herein, we show that a straightforward and effective combination of wet spinning and twisting technique enables continuously fabricating RTP fibers with twisting‐induced helical chirality. By leveraging the hydrogen bonding interactions between polyvinyl alcohol (PVA) and quinoline derivatives, along with the rigid microenvironment provided by PVA chains, typically, Q‐NH2@PVA fiber demonstrates outstanding phosphorescent characteristics with RTP lifetime of 1.08 s and phosphorescence quantum yield of 24.6%, and the improved tensile strength being 1.7 times than pure PVA fiber (172 ± 5.82 vs 100 ± 5.65 MPa). Impressively, the transformation from RTP to circularly polarized room temperature phosphorescence (CP‐RTP) is readily achieved by imparting left‐ or right‐hand helical structure through simply twisting, enabling large‐scale production of chiral Q‐NH2@PVA fiber with dissymmetry factor of 10‐2. Besides, an array of displays and encryption patterns are crafted by weaving or seaming to exemplify the promising applications of these PVA‐based fibers with outstanding adaptivity in cutting‐edge anti‐counterfeiting technology.

Thermally Enhanced Phosphorescent Carbon Nanodots for Monitoring Cold-Chain Logistics.

Room-temperature phosphorescent materials, renowned for their long luminescence lifetimes, have garnered significant attention in the field of optical materials. However, the challenges posed by thermally induced quenching have significantly hindered the advancement of luminescence efficiency and stability. In this study, thermally enhanced phosphorescent carbon nanodots (CND) are developed by incorporating them into fiber matrices. Remarkably, the phosphorescence lifetime of the thermally enhanced CND exhibits a twofold enhancement, increasing from 326 to 753ms, while the phosphorescence intensity experienced a tenfold enhancement, increasing from 25 to 245 as the temperature increased to 373K. Rigid fiber matrices can effectively suppress the non-radiative transition rate of triplet excitons, while high temperatures can desorb oxygen adsorbed on the surface of the CND, disrupting the interaction between the CND and oxygen. Consequently, a thermally enhanced phosphorescence is obtained. In addition, benefiting from the thermally enhanced phosphorescence property of CND, a warning indicator with an anti-counterfeiting function for monitoring cold-chain logistics is demonstrated based on CND.

Achieving Colorful Ultralong-Lifetime Room-Temperature Phosphorescence Based on Benzocarbazole Derivatives through Resonance Energy Transfer.

It is of practical significance to develop polymer-based room-temperature phosphorescence (RTP) materials with ultralong lifetime and multicolor afterglow. Herein, the benzocarbazole derivatives were selected and combined with a poly(vinyl alcohol) (PVA) matrix by a coassembly strategy. Owing to the hydrogen-bonding interactions between benzocarbazole derivatives and the PVA matrix, the nonradiative transition and the quenching of triplet excitons are effectively inhibited. Therefore, the maximum phosphorescence emission lifetime of 2202.17 ms from ABfCz-PVA and the maximum phosphorescence quantum efficiency of 34.97% from ABtCz-PVA were obtained, respectively. In addition, commercially available dye molecules were selected to construct phosphorescent resonance energy transfer (PRET) systems for energy acceptors, enabling full-color afterglow emission in blue, green, yellow, red, and even white. Based on the characteristics of prepared RTP materials, multifunctional applications to flexibility, information encryption, and erasable drawing were deeply explored.

Scalable fabrication of red Room-Temperature phosphorescent materials through molecular doping strategy for versatile applications

Room-temperature phosphorescence (RTP) materials renowned for their long emission lifetime have garnered tremendous research interest not only for elucidating their underlying mechanisms but also for exploring their potential applications in anti-counterfeiting, encryption, and bioimaging. Nevertheless, the RTP color of most organic materials has been limited to blue, green, and yellow. In this study, a series of red RTP materials have been successfully fabricated at a large scale through a straightforward molecular doping strategy. Remarkably, the doped materials exhibited red RTP at 622 nm and 678 nm with an ultralong lifetime of 373 ms and an efficiency of 5.21 %, which was among the best performances reported for organic RTP materials. The systematic investigation unveiled that the efficient RTP emanated from the robust interactions between the emitter and matrix molecules as well as the formation of D/A exciplexes. Furthermore, the red RTP materials could be easily manufactured into diverse forms, including fine powders, aqueous inks, and nanoparticles. Their multifunctional applications in fingerprint recognition, encryption, and live bioimaging were demonstrated. With distinctive advantages such as red RTP, ultralong lifetime, scalable production, and cost-effectiveness, these RTP materials pave the way for the extensive utilization of organic RTP materials in various engineering sectors.

Ultra-long room temperature phosphorescent materials based on tetraphenylethylene derivatives for anti-counterfeiting and encryption applications

Stimuli-responsive room temperature phosphorescent materials have been the subject of considerable research activity in recent years. In this study, the tetraphenylethylene group was selected in combination with arylboronic acid (TIPE-BOH) and used to dope a rigid polyvinyl alcohol (PVA) matrix to generate a film material (TIPE-BOH-PVA) that exhibited an aggregation-induced emission (AIE) effect. The prepared film exhibits excellent room temperature phosphorescence (RTP) performance, with an enhanced emission wavelength and an afterglow time of up to 12 s. The triplet-to-singlet Förster resonance energy transfer (TS-FRET) has been utilized to modify the afterglow color by adding butyl rhodamine B (BRhB) and rhodamine 6G (R6G), employing a water phase without the use of organic solvents. The resultant material exhibits stimulus responsiveness; the RTP properties disappear when the material is exposed to water vapor, but are restored following thermal treatment. The material has potential applications in information encryption and erasure, double anti-counterfeiting ink, and fingerprint acquisition systems. This work offers a new strategy for the design of stimuli-responsive ultra-long RTP materials with far-ranging end applications.

A carbon dot-based time-dependent color-changing room temperature phosphorescent material with facile synthesis.

Carbon dots have attracted widespread attention due to their excellent optical properties and so on and are therefore used in various fields such as anti-counterfeiting. There are many reports on carbon dot-based room-temperature phosphorescent materials, but there are still fewer reports on carbon dot-based room-temperature phosphorescent materials with time-dependent color-changing properties. In this work, a time-dependent color-changing carbon dot-based room-temperature phosphorescent material with the ability to change from green to blue was successfully prepared by a simple one-pot heating method using hydroxyurea as the only raw material. In this process, hydroxyurea is used as both a carbon and nitrogen source, and in the process of material formation, hydroxyurea also partially forms cyanuric acid as a matrix to make the carbon dots uniformly dispersed in it. By blending the ratio of the dual emission centers of the carbon dots themselves, the final effect of time-dependent color-changing is achieved by taking advantage of the intensity changes and color differences of each emission center. The present work provides new ideas for the preparation of time-dependent color-changing carbon dot-based room-temperature phosphorescent materials.

Purely Organic Room‐Temperature Phosphorescence Molecule for High‐Performance Non‐Doped Organic Light‐Emitting Diodes

Purely organic molecules with room‐temperature phosphorescence (RTP) are potential luminescent materials with high exciton utilization for organic light‐emitting diodes (OLEDs), but those exhibiting superb electroluminescence (EL) performances are rarely explored, mainly due to their long phosphorescence lifetimes. Herein, a robust purely organic RTP molecule, 3,6‐bis(5‐phenylindolo[3,2‐a]carbazol‐12(5H)‐yl)‐xanthen‐9‐one (3,2‐PIC‐XT), is developed. The neat film of 3,2‐PIC‐XT shows strong green RTP with a very short lifetime (2.9 μs) and a high photoluminescence quantum yield (72%), and behaviors balanced bipolar charge transport. The RTP nature of 3,2‐PIC‐XT is validated by steady‐state and transient absorption and emission spectroscopies, and the working mechanism is deciphered by theoretical simulation. Non‐doped multilayer OLEDs using thin neat films of 3,2‐PIC‐XT furnish an outstanding external quantum efficiency (EQE) of 24.91% with an extremely low roll‐off (1.6%) at 1000 cd m‒2. High‐performance non‐doped top‐emitting and tandem OLEDs are also achieved, providing remarkable EQEs of 24.53% and 42.50%, respectively. Delightfully, non‐doped simplified OLEDs employing thick neat films of 3,2‐PIC‐XT are also realized, furnishing an excellent EQE of 17.79% and greatly enhanced operational lifetime. The temperature‐dependent and transient EL spectroscopies demonstrate the electrophosphorescence attribute of 3,2‐PIC‐XT. These non‐doped OLEDs are the best devices based on purely organic RTP materials reported so far.

Purely Organic Room-Temperature Phosphorescence Molecule for High-Performance Non-Doped Organic Light-Emitting Diodes.

Purely organic molecules with room-temperature phosphorescence (RTP) are potential luminescent materials with high exciton utilization for organic light-emitting diodes (OLEDs), but those exhibiting superb electroluminescence (EL) performances are rarely explored, mainly due to their long phosphorescence lifetimes. Herein, a robust purely organic RTP molecule, 3,6-bis(5-phenylindolo[3,2-a]carbazol-12(5H)-yl)-xanthen-9-one (3,2-PIC-XT), is developed. The neat film of 3,2-PIC-XT shows strong green RTP with a very short lifetime (2.9 μs) and a high photoluminescence quantum yield (72%), and behaviors balanced bipolar charge transport. The RTP nature of 3,2-PIC-XT is validated by steady-state and transient absorption and emission spectroscopies, and the working mechanism is deciphered by theoretical simulation. Non-doped multilayer OLEDs using thin neat films of 3,2-PIC-XT furnish an outstanding external quantum efficiency (EQE) of 24.91% with an extremely low roll-off (1.6%) at 1000 cd m‒2. High-performance non-doped top-emitting and tandem OLEDs are also achieved, providing remarkable EQEs of 24.53% and 42.50%, respectively. Delightfully, non-doped simplified OLEDs employing thick neat films of 3,2-PIC-XT are also realized, furnishing an excellent EQE of 17.79% and greatly enhanced operational lifetime. The temperature-dependent and transient EL spectroscopies demonstrate the electrophosphorescence attribute of 3,2-PIC-XT. These non-doped OLEDs are the best devices based on purely organic RTP materials reported so far.

High pH Stability and Ultralong‐Lived Room Temperature Phosphorescence Carbon Dots in Aqueous Environment

AbstractLong‐lived room temperature phosphorescence (RTP) materials have many potential applications in areas such as luminescent lighting, biological imaging, and information security owing to their unique optical properties. However, traditional RTP materials are challenged by the fact that their phosphorescence can be easily quenched by dissolved oxygen and solvent‐assisted relaxation, making it difficult for them to emit phosphorescence in aqueous solutions, particularly in extreme pH environments. In this study, a multicolor RTP carbon dot‐based composite material (u‐CDs) is developed with urea and 3‐aminophenylboronic acid as raw materials. This material exhibits ultra‐long phosphorescence emission lifetime and high pH stability by constructing a rigid hydrogen bond network structure in an aqueous environment. The u‐CDs have an optimal emission of 448 nm, a quantum yield of 21.6%, a phosphorescence lifetime of 2.35 s, and an afterglow time of more than 50 s. With such unique properties, u‐CDs have great potential for applications in anti‐counterfeiting, information encryption, and 3D printing.

A co-doping strategy to fabricate ultralong organic room temperature phosphorescence (ORTP) materials: Designing, preparation and advanced applications

Isophthalic acid (IPA) is a star phosphorescence molecule, which is a commercially available raw material with simple chemical structure, but is of good phosphorescence performance. However, the great research vacancy is still maintained because of its limited applications. Absolutely, polymer-matrix strategy is a common method to produce phosphorescence amorphous material by dispersing IPA into matrix such as polyvinyl alcohol (PVA). But how to further optimize the phosphorescence property of the resulted doping material (PVA-IPA)? Up to now, this question is new and very little attention has been paid. In this work, a co-doping strategy was explored, that is, charging the second dopant of ClCH2COOH into PVA-IPA was verified as a promising method to further enhance the phosphorescence property of PVA-IPA, leading to the co-doping material PVA-IPA-ClCH2COOH with ultralong phosphorescence lifetime as 500 ms and high phosphorescence quantum yield (ΦP) as 23.7%. Depending on these promising phosphorescence behaviors, PVA-IPA-ClCH2COOH was successfully applied in the fields of information anti-counterfeiting and artificial light harvest.

3-Ethynyltriimidazo[1,2-a:1',2'-c:1″,2″-e][1,3,5]triazine Dual Short- and Long-Lived Emissions with Crystallization-Enhanced Feature: Role of Hydrogen Bonds and π-π Interactions.

Organic room temperature phosphorescent (ORTP) materials with stimuli-responsive, multicomponent emissive behaviour are extremely desirable for various applications. The derivative of cyclic triimidazole (TT) functionalized with an ethynyl group, TT-CCH, is isolated and investigated. The compound possesses crystallization-enhanced emission (CEE) comprising dual fluorescence and dual phosphorescence of both molecular and supramolecular origin with aggregation-induced components highly sensitive to grinding. The mechanisms involved in the emissions have been disclosed thanks to combined structural, spectroscopic and computational investigations. In particular, strong CH⋯N hydrogen bonds are deemed responsible, for the first time in the TT family, together with frequently observed π⋯π stacking interactions, for the aggregated fluorescence and phosphorescence.

3D Printed Room Temperature Phosphorescence Materials Enabled by Edible Natural Konjac Glucomannan.

Shaping room temperature phosphorescence (RTP) materials into 3D bodies is important for stereoscopic optoelectronic displays but remains challenging due to their poor processability and mechanical properties. Here, konjac glucomannan (KGM) is employed to anchor arylboronic acids with various π conjugations via a facile B─O covalent reaction to afford printable inks, using which full-color high-fidelity 3D RTP objects with high mechanical strength can be obtained via direct ink writing-based 3D printing and freeze-drying. The doubly rigid structure supplied by the synergy of hydrogen bonding and B─O covalent bonding can protect the triplet excitons; thus, the prepared 3D RTP object shows a striking lifetime of 2.14 s. The printed counterparts are successfully used for 3D anti-counterfeiting and can be recycled and reprinted nondestructively by dissolving in water. This success expands the scope of printable 3D luminescent materials, providing an eco-friendly platform for the additive manufacturing of sophisticated 3D RTP architectures.

Multifunctional applications of organic light-emitting diodes and room temperature phosphorescence based on benzoyl-fluorene hybrid molecules

Organic light-emitting diodes (OLEDs) and room temperature phosphorescence (RTP) materials have attracted great interests for their wide application in lighting and other fields. How to efficiently utilize triplet excitons to achieve the multifunctionality of OLED and RTP simultaneously is a major challenge. Herein, two blue molecules, 3PCZFB and 3PCZBF were reported. Theoretical calculations indicate that both molecules possess hybrid localized charge transfer (HLCT) characteristic. More importantly, both can simultaneously obtain electro-fluorescence and RTP properties by multiple harvesting of triplet excitons with high spin-orbit coupling matrix element (SOCME). The introduction of benzoyl fluorene increased the contribution of the n-orbital, resulting in a high SOCME, which is beneficial to both high exciton utilization efficiency (EUE) and RTP. The non-doped OLED of 3PCZFB achieved maximum external quantum efficiency (EQEmax) of 4.9 % and EUE of 58.6 % at 459 nm. Besides, 0.1 % 3PCZFB and 3PCZBF doped in PMMA sheets achieve RTP efficiencies of 6.6 % at 524 nm and 25.9 % at 506 nm, as well as lifetimes of 379.8 ms and 204.8 ms. This is the first time Benzoyl fluorene-based molecules achieved dual-function applications in OLED and RTP by utilizing and recycling triplet excitons of T1.

Achieving Efficient Dark Blue Room-Temperature Phosphorescence with Ultra-Wide Range Tunable-Lifetime.

Tunable-lifetime room-temperature phosphorescence (RTP) materials have been widely studied due to their broad applications. However, only few reports have achieved wide-range lifetime modulation. In this work, ultra-wide range tunable-lifetime efficient dark blue RTP materials were realized by doping methyl benzoate derivatives into polyvinyl alcohol (PVA) matrix. The phosphorescence lifetimes of the doped films can be increased from 32.8 ms to 1925.8 ms. Such wide range of phosphorescence lifetime modulation is extremely rare in current reports. Moreover, the phosphorescence emission of the methyl 4-hydroxybenzoate-doped film is located in the dark blue region and the phosphorescence quantum yield reaches as high as 15.4 %, which broadens their applications in organic optoelectronic information. Further studies demonstrated that the reason for the tunable lifetime was that the magnitude of the electron-donating ability of the substituent group modulates the HOMO-LUMO and singlet-triplet energy gap of methyl benzoate derivatives, as well as the ability to non-covalent interactions with PVA. Moreover, the potential applications of luminescent displays and optical anti-counterfeiting of these high-performance dark blue RTP materials have been conducted.