Phosphorescence Quantum Efficiency Research Articles

Visualization Detection of Ultralow Temperature Based on Flexible Cross–linked Polymer Systems

AbstractUltralow temperature storage has sparked considerable attention with the development of the economy, showing promising applications ranging from biomedical to national defense and other fields. However, the development of ultralow temperature detection is constrained by the brittleness of current materials at low temperatures and the complexity of detection techniques. Consequently, the challenge exists in finding efficient solutions to material tolerance issues and achieving rapid detection of ultralow temperature. Herein, a novel flexible cross–linked polymer TPTA@PU film with long afterglow, high phosphorescence quantum efficiency, and excellent mechanical properties are successfully fabricated. Interestingly, the obtained TPTA@PU films demonstrate a notable thermoresponsive behavior, with the afterglow color shifting rapidly from blue to green within the temperature ranges from 80 to 280 K. Additionally, there is a positive linear correlation between the RGB values of the afterglow color and the corresponding temperature. Based on these prominent features, an ultralow temperature sensor is realized by utilizing TPTA@PU films as thermoresponsive elements. This work can be expected to provide more inspiration and possibilities for using RTP materials in a more cutting‐edge field.

Organic doped red room-temperature afterglow materials based on 2,3,5-triarylfuro[3,2-b]pyridines through Förster-resonance energy transfer

A series of novel 2,3,5-triarylfuro[3,2-b]pyridines are designed and acquired to be used as the guest molecules in organic doped room-temperature phosphorescence (RTP) system. Phenyl(pyridin-2-yl)methanone which can provide the rigid and tight microenvironment is chosen as the host molecule, which enables the two-component doped materials to emit RTP emissions of 0.5–8 s with 41–565 ms phosphorescence lifetimes and 2.9–19.4 % phosphorescence quantum efficiencies through constricting the non-radiative decay of triplet excitons. Furthermore, using commercial dyes Erythrosin B sodium salt and Eosin Y sodium salt as the third component and energy acceptor, the three-component materials emit bright red afterglows of 2 s with delayed lifetimes of 252–286 ms and emission quantum yields of 5.1–5.6 %, which are demonstrated to come from the triplet-to-singlet Förster-resonance energy transfer (FRET) from phosphorescence emission of 2,3,5-triarylfuro[3,2-b]pyridine derivative to fluorescence emission of commercial dye. This work not only provides valuable reference for the development of furo[3,2-b]pyridine-based afterglow materials, but also proves that the strategy of the FRET process provides new possibilities for molecules that can only emit fluorescence to participate in constructing afterglow materials.

Modulating Heavy Atom Effect in Germylene for Persistent Room Temperature Phosphorescence.

It is worth but still challenging to develop the low-valent main group compounds with persistent room temperature phosphorescence (pRTP). Herein, we presented germylene-based persistent phosphors by introduction of low-valent Ge center into chromophore. A novel phosphors CzGe and its series of derivatives, namely CzGeS, CzGeSe, CzGeAu, and CzGeCu, were synthesized. Experiments and theoretical calculations reveal that the pRTP behavior were "turn on" due to the heavy atom effect of germylene. More importantly, the low-valent of oxidation state and structural traits propelled GeCz had a balance between the intersystem crossing and the shortening of lifetime caused by the heavy atoms, resulting the ultralong lifetime of 309 ms and phosphorescent quantum efficiency of 15.84 %, which is remarkable among heavy main group phosphors. This research provides valuable insights to the design of heavy atoms in phosphors and expand the applications of germylene chemistry.

Nylons with Highly-Bright and Ultralong Organic Room-Temperature Phosphorescence

Endowing the widely-used synthetic polymer nylon with high-performance organic room-temperature phosphorescence would produce advanced materials with a great potential for applications in daily life and industry. One key to achieving this goal is to find a suitable organic luminophore that can access the triplet excited state with the aid of the nylon matrix by controlling the matrix-luminophore interaction. Herein we report highly-efficient room-temperature phosphorescence nylons by doping cyano-substituted benzimidazole derivatives into the nylon 6 matrix. These homogeneously doped materials show ultralong phosphorescence lifetimes of up to 1.5 s and high phosphorescence quantum efficiency of up to 48.3% at the same time. The synergistic effect of the homogeneous dopant distribution via hydrogen bonding interaction, the rigid environment of the matrix polymer, and the potential energy transfer between doped luminophores and nylon is important for achieving the high-performance room-temperature phosphorescence, as supported by combined experimental and theoretical results with control compounds and various polymeric matrices. One-dimensional optical fibers are prepared from these doped room-temperature phosphorescence nylons that can transport both blue fluorescent and green afterglow photonic signals across the millimeter distance without significant optical attenuation. The potential applications of these phosphorescent materials in dual information encryption and rewritable recording are illustrated.

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.

Host-guest doped room/high-temperature phosphorescence of diarylfuro[3,2-b]pyridine derivatives

Due to the high temperature that can easily lead to non-radiative transitions of triplet excitons, obtaining high-temperature phosphorescence (HTP) materials is challenging. Herein, using diarylfuro[3,2-b]pyridines as the guest molecules and polyacrylic acid (PAA) as the host molecule, the two-component doped materials exhibit green room-temperature phosphorescence (RTP) with afterglow times of 2–8 s, delayed lifetimes of 256–939 ms, and phosphorescence quantum efficiencies of 140.3–21.2 %, and green HTP emissions with 2 s afterglow and 208 ms delayed lifetime at 373 K. The HTP activity of the doped system originates from the rigid environment provided by PAA, planar and rigid molecular structures of diarylfuro[3,2-b]pyridines, and strong interactions between PAA and diarylfuro[3,2-b]pyridines. Furthermore, using organic small molecules as the reference host molecules, compared to benzophenone, 5-methylphthalic anhydride, and butane-1,2,3,4-tetracarboxylic acid with chemical structures similar to PAA result in better RTP/HTP properties, revealing that strong interactions between host and guest molecules play a very important role in ultralong phosphorescence emissions of these host–guest doped materials. Moreover, these doped materials based on diarylfuro[3,2-b]pyridines can be developed as advanced anti-counterfeiting and encryption materials. This result provides valuable reference for developing excellent RTP/HTP materials based on N,O-containing fused-ring compounds.

Carbon Dot/Al2O3 Nanocomposites with an Enhanced Lifetime, Phosphorescence Quantum Efficiency, and Stability for Anticounterfeiting Applications

Carbon Dot/Al₂O₃ Nanocomposites with an Enhanced Lifetime, Phosphorescence Quantum Efficiency, and Stability for Anticounterfeiting Applications

Incorporation of deuterated coronene into cage-like sodalite-type porous organic salts and improvement of room-temperature phosphorescence properties

Abstract Host materials with external heavy atom effects do not change the chemical structures of incorporated luminescent molecules but promote intersystem crossing from the excited singlet state to the excited triplet state, which induces room-temperature phosphorescence (RTP). The deuteration of luminescent molecules suppresses non-radiative deactivation via C–H stretching vibration; therefore, the improvement of both phosphorescence lifetime and quantum efficiency (i.e. isotope effect) is expected. Although a combination of the external heavy atom effect and isotope effect could be expected to improve phosphorescent performances dramatically, an environment with a strong external heavy atom effect (density of iodine atoms ≥0.65 gcm−3) increases non-radiative deactivation via spin-orbit coupling; therefore, the isotope effect is hindered, and the phosphorescent lifetime and quantum efficiency are not usually improved. In the current work, we constructed cage-like sodalite-type porous organic salts (s-POSs) where the density of iodine atoms (0.55 gcm−3) was moderate (0.13 ̶ 0.65 gcm−3). Incorporation of a deuterated representative luminescent molecule such as coronene (coronene-d12) into s-POSs enabled the exerting of both the external heavy atom effect and isotope effect, which successfully improved both RTP lifetime (1.1 times) and quantum efficiency (1.6 times) over those of an incorporated ordinary coronene (coronene-h12).

Ultralong afterglow of heavy-atom-free carbon dots with a phosphorescence lifetime of up to 3.7 s for encryption and fingerprinting description.

Metal-free room-temperature phosphorescent (RTP) materials with changeable colors have attracted great attention in anti-counterfeiting information encryption. Most ultralong-lifetime RTP (URTP) luminophores are traditionally obtained through heavy atom effects via enhancing the spin-orbit coupling efficiency. Here, we report the self-assembly of URTP carbon dots (CDs) using diphenylaminourea as the precursor through a thermal-evaporation assisted covalent-binding approach in the presence of boric acid (BA). The BA-functionalized diphenylaminourea-derived CDs (denoted as D-CDs1.5/BA composites) show a rigid network structure with B-C linkages connected to the surface of the CDs, which can effectively suppress the free vibration of CDs to promote intersystem crossover, finally resulting in an excellent URTP afterglow performance. They feature a low singlet-triplet energy gap and reduced nonradiative attenuation properties. As a result, the D-CDs1.5/BA composites exhibit a bifunctional fluorescence/phosphorescence performance with a high phosphorescence quantum efficiency (12.67%) and an ultra-long green afterglow phosphorescence lifetime of up to 3.66 s. A high-level information encryption and fingerprinting description based on the URTP D-CDs1.5/BA composites were then investigated. This work contributes to the feasible design and preparation of novel URTP CD materials with both ultra-long afterglow and a high phosphorescence efficiency, making them promising candidates for advanced anti-counterfeiting applications.

High-Quality Circularly Polarized Organic Afterglow from Nonconjugated Amorphous Chiral Copolymers.

Organic materials featuring circularly polarized luminescence (CPL) and/or afterglow emission represent an active research frontier with promising applications in various fields, but the achievement of high-performance CPL organic afterglow (CPOA) remains a huge challenge due to the intrinsic contradictions between the luminescent lifetime/dissymmetry factor (glum) and phosphorescent quantum efficiency (PhQY). Herein, we report a simple and universal approach to design efficient CPOA from amorphous copolymers by incorporating chiral chromophores into a nonconjugated clusterization-triggered emissive polymer with plenty of hydron-bonding interactions, followed by aggregation engineering using water dissolution and evaporation. With this chiral copolymerization and aggregation engineering (CCAE) strategy, high-performance CPOA polymers with PhQYs of up to 6.32%, ultralong lifetimes of over 650 ms, glum values of 3.54 × 10-3, and the highest figure-of-merit were achieved at room temperature. Given the impressive CPOA performance of these polymers, the applications in multilevel data anticounterfeiting and reversible displays with high stability were demonstrated. These findings through the CCAE strategy to overcome the inherent restraints of CPOA materials lay the foundation for the development of amorphous polymers with superior CPOA, significantly expanding the understanding of CPL and the design of organic afterglow materials.

Inorganic salt recrystallization strategy for achieving ultralong room temperature phosphorescence through structural confinement and aluminized reconstruction

Achieving highly efficient and stable room temperature phosphorescence (RTP) with ultralong lifetime is critical for the multi-purpose applications of phosphorescent materials. In this work, we propose an inorganic salt heating recrystallization strategy to simultaneously improve the lifetime, quantum efficiency, and stability of phosphorescent scandium/leucine microspheres (Sc/Leu-MSs). Inorganic salt-treated Sc/Leu-MSs are obtained by simply heating and drying inorganic salt solution containing Sc/Leu-MSs, which can achieve a maximum lifetime increase of 4.42-times from 208.37 ms (Sc/Leu-MSs) to 920.08 ms (Al2(SO4)3-treated Sc/Leu-MSs), accompanied by a RTP intensity increase up to 24.08-times. The enhancement mechanism of RTP efficiency is attributed to the stabilization of triplet excitons caused by inorganic salt coating that suppresses molecular motion and isolates oxygen on the one hand, and the efficient intersystem crossing promoted by aluminized reconstruction-caused duplex heavy atom effects on the other hand. This study provides new design principle and a facile strategy to construct RTP materials with ultralong lifetime, high phosphorescent quantum efficiency, and high stability for promising applications such as anti-counterfeiting and light emitting diodes.

A theoretical study on the electronic structures and phosphorescence properties of light-emitting electrochemical cell champions reported in early 2022

The electronic structure, absorption properties, phosphorescence quantum efficiency and emission spectra, of a series of iridium(III) complexes containing phenyltriazole-type cyclometallated ligands (1–4) were studied using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The simulated electronic/photophysical properties of the iridium complexes are in good agreement with the experimental observations. The results of the calculations show that the lowest lying singlet absorptions for 1–4 are located at 3.83, 3.91, 3.01, and 2.98 eV, respectively. All complexes show emissions characterised as a mixture of triplet ligand-to-ligand charge transfer (3LLCT) and metal-to-ligand charge transfer (3MLCT) states. The fluorination of the attached phenyl groups (complex 2) and the introduction of –CF3 moieties (complex 3) in the phenyltriazole cyclometallated ligands results in a strong interaction in the T1 states, due to the contracted Ir–Ns bonds with the bpy ancillary ligand. Therefore, both complexes show a moderate contribution of the metal character (%Mc), a lower energy gap between the T1 and the S1 states (ΔET1-S1) together with the largest transition dipole moment (μS1), resulting in an enhanced phosphorescence quantum efficiency. The introduction of –CH3 groups (complex 4) in the phenyltriazole cyclometallated ligands stabilises the triplet metal-centred (3MC) state, resulting in a fast nonradiative decay along with a lower quantum yield. The vertical emission energies calculated at the B3LYP level for the 1–4 complexes are located at 2.60, 2.38, 2.68, and 2.62 eV, respectively. Based on these results, the theoretical calculations can provide an accurate prediction of the electronic and the photophysical properties of iridium complexes, and then can be used to guide the synthesis of new phosphorescent materials.

Boosting the Phosphorescence Efficiency in Doped Organic Crystals: Critical Role of Hydrogen Bonding.

Host-guest doping systems with phthalimides (BI) and N-methylphthalimide (NMeBI) as the host and 1,8-naphthalimide (NI) and 4-bromo-1,8-naphthalimide (4BrNI) as the guest have been developed. The 0.2% NI/BI (molar ratio) with a strong C=O···H-N hydrogen bond exhibited a phosphorescence quantum efficiency (29.2%) higher than that of NI/NMeBI with a weak C=O···H-C hydrogen bond (10.1%). A similar trend was observed in the 4BrNI guest system. A remarkable phosphorescent efficiency of 42.1% was achieved in a 0.5% 4BrNI/BI composite, which represents the highest value in NI-based phosphors. This research indicates stronger hydrogen bonding may have a greater contribution in boosting the phosphorescence efficiency.

Ultra‐Long Room Temperature Phosphorescence with the Efficiency Over 64% Induced by 1‰ Impurity Doping

AbstractUltra‐long room temperature phosphorescence (ULRTP) materials show valuable applications in encryption, biological imaging, and many other fields. Amazingly, the concomitant impurities from raw materials that are normally ignored contribute dramatically to the ULRTP. In this study, CzPMB [9‐(4‐bromo‐3‐methylphenyl)‐9H‐carbazole] with phosphorescent quantum efficiency of 64% is prepared from commercial carbazole, but the phosphorescent efficiency is drastically reduced to < 2% once trace impurity (5‐(4‐bromo‐3‐methylphenyl)‐5H‐benzo[b]carbazole) is separated. HPLC studies demonstrated the separated impurity is a byproduct derived from trace benzocarbazole in commercial carbazole. Subsequently, the ULRTP for the CzPMB synthesized from lab‐made carbazole is totally unobserved, strongly confirming the dramatic impact of impurity. A defect trapping mechanism in multicomponent system rather than heavy atom effect is proposed for highly efficient ULRTP after carefully analyzing the crystal packings and molecular energy levels. Inspired by this discovery, a series of effective ULRTP bi‐component systems with the highest phosphorescence efficiency of 64.1% are reproduced by directed host‐guest doping. This strategy paves a viable path for the design of organic materials with highly efficient ULRTP.

Suppression of nonradiative transitions of triplet excitonsviaa fused/non-fused strategy for realizing efficient room-temperature phosphorescence

Through transformation of non-fused ring structure into fused-ring structure, the phosphorescence quantum efficiency of room temperature phosphorescence materials containing sulfur atoms and carbonyl groups in doped films increased from 0.3% to 47.0%.

A Molecular Engineering Strategy for Achieving Blue Phosphorescent Carbon Dots with Outstanding Efficiency above 50.

Highly efficient emission has been a long-lasting pursuit for carbon dots (CDs) owing to their enormous potential in optoelectronic applications. Nevertheless, their room-temperature phosphorescence (RTP) performance still largely lags behind their outstanding fluorescence emission, especially in the bluespectral region. Herein, high-efficiency blue RTP CDs have been designed and constructed via a simple molecular engineering strategy, enabling CDs with an unprecedented phosphorescence quantum efficiency of to 50.17% and a long lifetime of 2.03 s. This treating route facilitates the formation of high-density (n, π*) configurations in the CD π-π conjugate system through the introduction of abundant functional groups, which can evoke a strong spin-orbit coupling and further promote the intersystem crossing from singlet to triplet excited states and radiative recombination from triplet excited states to ground state. With blue phosphorescent CDs as triplet donors, green, red, and white afterglow composites are successfully fabricated via effective phosphorescence Förster resonance energy transfer. Importantly, the color temperature of the white afterglow emission can be widely and facilely tuned from cool white to pure white and warm white. Moreover, advanced information encryption, light illumination, and afterglow/dynamic visual display have been demonstrated when using these multicolor-emitting CD-based afterglow systems.

Excitation‐Dependent and Efficient Phosphorescence Based on Benzophenone Derivatives

AbstractThe design of organic molecules with high photoluminescence quantum efficiency and adjustable emission colors has led to the development of high‐performance optoelectronic devices. However, the task of generating color‐tunable luminescence originating from different excited states has achieved limited success. Here, a design strategy is presented for improving phosphorescence quantum efficiency and extending emission spectral range by introducing high luminous acenes in benzophenone derivatives. The experimental data reveal that the maximum phosphorescence efficiency of the designed molecule can reach 84% in solution and 61% in crystals, which is the most efficient benzophenone phosphor so far. Importantly, the excited states can be selectively expressed by varying the excitation wavelengths, including thermally activated delayed fluorescence (TADF) from T2 to S1 excited state, and dual phosphorescence from T2 and T1 excited states. The design strategy of using rigid acenes to suppress nonradiative transition provides an opportunity to improve phosphorescence efficiency comparable with fluorescence efficiency, presenting great potential in high‐performance optoelectronic devices.

Recent Advances in Organic Room-Temperature Phosphorescence of Heteroatom (B/S/P)-Containing Chromophores

Recent Advances in Organic Room-Temperature Phosphorescence of Heteroatom (B/S/P)-Containing Chromophores

Ultra-stable dual-color phosphorescence Carbon-Dot@Silica material for advanced anti-counterfeiting

Room temperature phosphorescence (RTP) materials have motivated massive attention due to their great advantages in anti-counterfeiting and optical encryption. However, the commonly used carbon-based RTP materials suffer from drawbacks of photobleaching, quenching and single phosphorescence color outputs, which obstruct their performance in high-level anti-counterfeiting techniques. Herein, we present a universal method for the fabrication of a carbon-dot@silica (CDs@SiO2) composite that possesses ultralong lifetime, high phosphorescence quantum efficiency (PQE), excellent luminescence stability, and dual-color phosphorescence emission. Taking advantage of the restriction by rigid network of SiO2 and stable covalent bonding between CDs and SiO2, the triplet excited states of CDs are stabilized. As a result, the CDs@SiO2 exhibit ultralong lifetime of 1.33 s and 0.38 s under excitation at 254 nm and 365 nm, respectively. Furthermore, the phosphorescence color of CDs@SiO2 can change from cyan to yellow when the exciting wavelength switches from 254 nm to 365 nm. The obtained CDs@SiO2 also exhibit outstanding characteristics of anti-photobleaching and phosphorescence stability in an aqueous solution. Based on the unique phosphorescent properties of the CDs@SiO2, a stable and dual-color phosphorescence security label is designed for advanced information encryption.

Orthogonal conformation regulation enables highly efficient phosphorescence emission in BODIPY-fluorene derivatives without heavy atoms

The BODIPY-Fluorene derivatives with an orthogonal conformation were prepared for the emission of efficient phosphorescence. The derivatives show visible light absorption (497–513 nm), high phosphorescence quantum efficiency (36.2%) and realize control of luminescence color from green to orange-red. Typical orthogonal conformation and smaller excited state (S1 and T4) energy gap (0.05 eV) are favorable for intersystem crossing (ISC) process. The calculation are carried out for rationalization between the photophysical properties and conformation of the BODIPY-Fluorene derivatives. We demonstrate that the conformational substitution positions and the distance between D-A are promising strategy to regulate the emission lifetime and quantum efficiency for BODIPY derivatives. Moreover, the ability to generate singlet oxygen was measured by photooxidation of 1,3-diphenylisobenzofuran (DPBF) by singlet oxygen (1O2) photosensitization. At the same time, the LED device displays bright orange-red emission. This work paves the way for further research into the design and application of such materials in advanced optics.