Pure Organic Room Temperature Phosphorescence Research Articles

High Efficiency Non‐Doped Organic Light Emitting Diodes Based on Pure Organic Room Temperature Phosphorescence by High‐Lying Singlet Exciton Fission

AbstractHeavy‐metal‐free pure organic room temperature phosphorescence (ORTP) holds great potential in the field of organic optoelectronic devices owing to low economic cost, simple preparation techniques, and high exciton utilization. However, it is still filled with challenges in realizing high efficiency organic light‐emitting diodes (OLEDs) and exploring the internal physical mechanism based on these ORTP molecules. Here, a high‐performance OLED induced by an unexpected interfacial spin‐mixing process between the ORTP molecule and interlayers is demonstrated, and the high efficiency electroluminescence (EL) mechanism is studied through magneto–electroluminescence (MEL) and magneto–photoluminescence (MPL) measurements. The steady‐state and transient PL properties imply that the interfacial effect is related to a high‐lying singlet fission (HLSF) process in the ORTP molecule itself. Further, the HLSF process and the corresponding energy level position are confirmed by the incident wavelength‐ and temperature‐dependent PL spectra and the magnetic‐field‐dependent transient PL. Finally, by optimizing the interfacial material adjacent to the emissive layer to utilize this interfacial spin mixing effect, a high‐efficiency non‐doped ORTP‐OLED with external quantum efficiency of 16% and CIE coordinates of (0.27, 0.49) is developed. The proposed mechanism during the EL process will give insight to produce more efficient OLEDs based on ORTP materials in the future.

Water-Soluble Luminescent Polymers with Room-Temperature Phosphorescence Based on the α-Amino Acids.

Nonconventional luminophores have received increasing attention, owing to their fundamental importance, advantages in outstanding biocompatibility, easy preparation, environmental friendliness, and potential applications in sensing, imaging, and encryption. Purely organic molecules with outstanding fluorescence and room-temperature phosphorescence (RTP) have emerged as a new library of benign afterglow agents. However, the cost, toxicity, high reactivity, and poor stability of materials also limit their practical applications. Therefore, some natural products, synthetic compounds, and biomolecules have entered horizons of people. The as-designed exhibits sky blue and green fluorescence emission and green RTP emission (a lifetime of 343ms and phosphorescence quantum of 15.3%) under air condition. This study presents an organic fluorescence for biological imaging and RTP for anti-counterfeiting and encryption based on amino acids, maleic anhydride and 4-vinylbenzenesulfonic acid sodium salt hydrate. This study provides a strategy for nonconventional luminophores in designing and synthesizing pure organic RTP materials.

A cucurbit[8]uril-based supramolecular phosphorescent assembly: Cell imaging and sensing of amino acids in aqueous solution

In recent years, host-guest interactions of macrocycles have emerged as a promising approach to effectively enhance pure organic room-temperature phosphorescence by inhibiting the nonradiative relaxation while isolating the effects of oxygen and water molecules. In this work, a supramolecular assembly Q[8]-BCPI was constructed by 6-bromoisoquinoline derivative (BCPI) and cucurbit[8]uril (Q[8]). The assembly produced intense green room temperature phosphorescence (RTP) emission and enabled supramolecular recognition and detection of l-tryptophan (L-Trp) and l-tyrosine (L-Tyr). Moreover, the Q[8]-BCPI assembly showed good biocompatibility and low biotoxicity, and had a good staining effect on HeLa cells.

Single component long-lived dynamic room temperature phosphorescence with large-scale preparation and visible light excitation

A pure organic room temperature phosphorescence (PORTP) luminogen named as DCP was successfully prepared and showed long room temperature phosphorescence (RTP) and afterglow lifetimes (3 ms and 4 s in sequence). Meanwhile, DCP showed high fluorescence (0.14) and RTP (0.39) quantum yields in crystalline state, simultaneously presented visible light excitation and dynamic RTP. By host-guest doping and optimization, Urea/DCP doping system emitted blue RTP, with RTP and afterglow lifetimes of 341 ms of 5 s in turn. Crystal analysis and theoretical calculations indicated H stacking, large spin orbit coupling constant, and small energy gap between the lowest singlet and triplet states result in long RTP lifetime and high quantum yield for DCP. Based on long phosphorescence emission, an advanced anti-counterfeiting pattern was constructed. As far as we know, it is the first report that such small molecules containing 3, 5-dicyanopyridine show long-lived RTP in both crystalline state and doping system. In this paper, not only ultralong and blue PORTP materials with the advantage of large-scale preparation, but also single component dynamic RTP, and RTP of visible light excitation were achieved.

Dual-Stimulus-Driven Dynamically Controllable [3]Rotaxane with Tunable Organic Room-Temperature Phosphorescence.

A dual-stimulus-driven stiff-stilbene-based dynamic [3]rotaxane has been facilely developed using the threading-stoppering strategy and exhibits reversible shuttling motions and bidirectional rotations upon encountering acid-base and distinct light stimulations, respectively. Herein, the two dibenzo-24-crown-8 macrocycles can undergo reversible switching motion between two different stations along the axle suffered from acid-base stimulation, and simultaneously, the two rotaxanes can also perform cis-trans rotations upon irradiation with distinct light. In other words, the constructed rotaxanes can conduct two modes of regular motions without interference. Interestingly, reciprocating switching motion of the rings along the axle enabled the rotaxanes to exhibit controllable and reversible photoisomerization speed, conversion yield, and quantum yield. Crucially, these rotaxanes also manifest adjustable solid-state organic room-temperature phosphorescence (RTP) and photoluminescence stimulated by dual factors (acid-base and diverse light), which are further applied in information encryption and anticounterfeiting. The presented study provides an instructive way for precisely boosting photoisomerization performances and the fabrication of dual-stimuli-induced molecular machines with functions of two-mode mechanical motions and controllable pure organic RTP switches.

Achieving color-tunable persistent afterglow from ultralong polyacrylamide-based room-temperature phosphorescence materials through phosphorescence Förster resonance energy transfer

Polymer-based pure organic room-temperature phosphorescence (RTP) materials have received widespread attention due to their great application prospects in many fields. However, the reports about polymer-based multicolor RTP materials were still rare. Herein, a series of monochromatic PAM-based RTP materials are constructed by facilely doping boric acid derivatives into polyacrylamide (PAM) matrices. Due to the strong intermolecular hydrogen-bonding interaction, 4-carboxyphenylboronic acid (CPBA) doped system PAM/CPBA achieves an ultralong RTP lifetime of 753 ms with a naked-eye visible blue afterglow up to 12 s. Significantly, PAM/CPBA as energy donor and the commercial fluorescent dye fluorescein (FL) or rhodamine B (RhB) as energy acceptor are used to fabricated ternary doping systems to achieve multicolor afterglow emission through phosphorescence Förster resonance energy transfer (FRET). The afterglow colors of PAM/CPBA/FL and PAM/CPBA/RhB can be easily adjusted from blue to yellow or purple by changing the doping content of FL or RhB. Inspiringly, a nearly white afterglow emission from the quaternary doping system PAM/CPBA/RhB/FL is achieved by varying the amount of FL content. Furthermore, the prepared PAM-based binary and ternary doping RTP materials can be applied in the field of information encryption.

Mechanochromism, tunable pure organic room temperature phosphorescence, single-molecule near-white emission, digital encryption, and anti-counterfeiting

The development of tunable pure organic room temperature phosphorescence and single-molecule white light emitters still faces a great challenge due to ineffective intersystem crossing and sensitive triplet excitons. Here, two phenothiazine based luminogens named PtzIP and PtzIPCN were designed and synthesized. PtzIP exhibits mechanochromic activity with hypsochromic shift of 25 nm, tunable room temperature phosphorescence from 613 nm to 530 nm and 560 nm, then to 540 nm and 585 nm by crushing and grinding, and single-molecule near-white light emission with the (CIE: Commission International de I'Eclairage) CIE coordinates of (0.33, 0.25), but PtzIPCN shows mechanochromism and room temperature phosphorescence inertness in crystalline state. By choosing polymethyl methacrylate (PMMA) and 4-fluorobenzophenone(F-BP) as host materials, as well PtzIP and PtzIPCN as guest materials, a series of host-guest doping systems were constructed and optimized by tuning doping ratio. PtzIP/PMMA and PtzIPCN/PMMA doping systems present concentration dependent fluorescence and phosphorescence emission, and RTP lifetime and afterglow of PtzIPCN/PMMA are up to 185.31 ms of 2.0 s. Furthermore, the lifetime of F-BP/PtzIPCN increases to 216.63 ms at doping ratio of 1:1000 for F-BP and PtzIPCN. Based on different luminescent properties of PtzIP and PtzIPCN in the doping systems, a series of high-level digital encryption and anti-counterfeiting patterns were successfully constructed. More importantly, the underlying mechanism behind luminescent properties were explored in detail by photophysical testing, crystal analysis, and theoretical calculations.

Recent Advances of Pure Organic Room Temperature Phosphorescence Based on Functional Polymers

Recent Advances of Pure Organic Room Temperature Phosphorescence Based on Functional Polymers

Accessing a Long‐Fluorescence‐Lifetime BODIPY Dye via Efficient Förster Resonance Energy Transfer Induced by Host‐Guest Doping

AbstractThe development of pure organic room temperature phosphorescence (RTP) luminophores with high quantum yield and long emission lifetime has attracted considerable attention due to their extensive optoelectronic and biomedical applications. The commonly used BODIPY dyes have strong UV‐Vis absorption, a relatively sharp emission peak, high quantum yield, and a short emission lifetime. By expending the molecular doping approach, we herein successfully achieved a long‐fluorescence‐lifetime BODIPY dye via efficient Förster resonance energy transfer (FRET) from RTP molecule o‐AI‐Cz to the short‐lived fluorescence emitter Bodipy‐2I. This host‐guest material possessed an ultralong lifetime of up to 595 ms and a long emission wavelength under ambient conditions, which has great potential in data encryption and anti‐counterfeiting applications. Moreover, this easily prepared FRET system exhibited an efficient response to two‐photon excitation in living cell fluorescence imaging.

A Heavy-atom-free Molecular Motif Based on Centrosymmetric Bird-like Structured Tetraphenylenes with Room-Temperature Phosphorescence (RTP) Afterglow over 8s.

In recent years, pure organic room-temperature phosphorescence (RTP) with highly efficient and long-persistent afterglow has drawn substantial awareness. Commonly, spin-orbit coupling can be improved by introducing heavy atoms into pure-organic molecules. However, this strategy will simultaneously increase the radiative and non-radiative transition rate, further resulting in dramatic decreases in the excited state lifetime and afterglow duration. Here in this work, a highly centrosymmetric bird-like structure tetraphenylene (TeP), and its three symmetrical halogenated derivatives (TeP-F, TeP-Cl and TeP-Br) are synthesized, while their RTP properties and mechanisms are systematically investigated by both theoretical and experimental approaches. As the results, the rigid, highly twisted conformation of TeP restricts the non-radiative processes of RTP and gives rise to the enhancement of electron-exchange, which can contribute to the RTP radiation process. Despite the faint RTP of the bromine and chlorine-substituted ones (TeP-Br, TeP-Cl), the fluoro-substituted TeP-F exhibited a long phosphorescent lifetime of up to 890 ms, corresponding to an extremely long RTP afterglow over 8 s, which could be incorporated into the best series of non-heavy-atom RTP materials reported in previous literature.

Switching Singlet Exciton to Triplet for Efficient Pure Organic Room-Temperature Phosphorescence by Rational Molecular Design.

The design and regulation of phosphors are attractive but challenging because of the spin-forbidden intersystem crossing (ISC) process. Here, a new perspective on the enhancement of the ISC is proposed and demonstrated. Different from current strategies, the ISC yield (ΦISC) is enhanced by decreasing the fluorescence radiative transition rate constant (kF) via rational molecular designing rather than boosting the spin-orbit coupling by decorating the molecular skeleton with a heavy atom, heteroatom, or carbonyl. The kF of the designed molecule in this case is associated with the substituent position of the methoxy group, which alters the distribution of the front orbitals. The S0 → S1 transition of these compounds evolves from a bright state to a dark state gradually with the variation of the substituent position, accompanied by the decrease of kF and increase of ΦISC. The fluorescence emission is switched to phosphorescence emission successfully by regulating the kF. This work provides an alternative strategy to design efficient room-temperature phosphorescence material.

Organic Binary and Ternary Cocrystal Engineering Based on Halogen Bonding Aimed at Room-Temperature Phosphorescence.

Recently, there has been intense interest in pure organic room-temperature phosphorescence (ORTP) from cocrystals composed of 1,4-diiodotetrafluorobenzene (DITFB) and a variety of polycyclic aromatic hydrocarbons (PAHs) or their derivatives. To expand the possibility of halogen bonding-based cocrystals, the relationship between the crystal packing motifs and ORTP characteristics in binary cocrystals composed of DITFB and PAHs of phenanthrene (Phen), chrysene (Chry), and pyrene (Pyr), respectively, is investigated. The σ-hole···π and π-hole···π interactions determine not only the crystal packing motifs but also photoluminescence quantum yields (PLQYs). The Phen-DITFB and Chry-DITFB binary cocrystals withσ-hole···πinteractions show higher PLQY compared with the Pyr-DITFB binary cocrystal with π-hole···πinteraction. Further, to clarify the effect of crystal structures on PLQY, ternary cocrystals are prepared by partially doping Pyr into Phen-DITFB. The crystal packing motif of the ternary cocrystal originates from a Phen-DITFB cocrystal with σ-hole···π interaction, and some of the Phen sites are randomly replaced with Pyr molecules. The ORTP emission is derived from Pyr. The maximum PLQY is >20% due to suppressing nonradiative decay by changing the crystal packing motif.

Observation of Chiral-selective room-temperature phosphorescence enhancement via chirality-dependent energy transfer

Pure organic room-temperature phosphorescence (RTP), particularly from guest-host doped systems, has seen exponential growth in the last several years due to their high modulation flexibility, and yet challenges remain with respect to mechanistic elucidations and advantageous applications. Here we show that by constructing guest-host doped RTP systems from chiral components, namely, chiral amino compound-modified phthalimide hosts and naphthalimide guests, a chiral-selective RTP enhancement phenomenon can be observed. For example, R-enantiomeric guests in R-enantiomeric hosts produce strong red RTP afterglow while no appreciable RTP could be observed in the S-R guest-host counterpart. An unprecedented RTP intensity difference > 102 folds with the ability to distinguish an enantiomeric excess of 98% could be achieved. Temperature-dependent measurements suggest that a chirality-dependent energy transfer process may be involved in the observed phenomenon, which can be harnessed to extend the RTP application to the chiral recognition of amino compounds, such as amino alcohols.

Heavy-element-free triplet accessibility in pyrene-core compounds at room temperature by microcrystal engineering

A micelle-assisted microcrystallization strategy was developed to achieve heavy-element-free pure organic room temperature phosphorescence in water.

Substitution Position Regulating the Excitation-Dependent Fluorescence-Phosphorescence Emission of Formylphenylboronic Acids for Single-Component White Light and Anticounterfeiting

With the development of pure organic room-temperature phosphorescence (ORTP), the study in excitation-dependent fluorescence-phosphorescence (ExDFPh) dual emission material is burgeoning. Herein, using formylphenylboronic acid (FPBA) as a prototype, the effect...

Solution-processed orange and white OLEDs sensitized by an electroactive pure organic room-temperature phosphorescent polymer

This work demonstrated solution-processed phosphorescence-sensitized fluorescence (PSF) with P(DMPAc-O-TPTrz) as the RTP sensitizer for TBRb. By facilely tuning the doping ratio of TBRb, efficient orange and white OLEDs are achieved.

Photoprogrammable circularly polarized phosphorescence switching of chiral helical polyacetylene thin films

The developments of pure organic room-temperature phosphorescence (RTP) materials with circularly polarized luminescence (CPL) have significantly facilitated the future integration and systemization of luminescent material in fundamental science and technological applications. Here, a type of photoinduced circularly polarized RTP materials are constructed by homogeneously dispersing phosphorescent chiral helical substituted polyacetylenes into a processable poly(methyl methacrylate) (PMMA) matrix. These substituted polyacetylenes play vital roles in the propagation of CPL and present prominently optical characteristics with high absorption and luminescent dissymmetric factors up to 0.029 (gabs) and 0.019 (glum). The oxygen consumption properties of the films under UV light irradiation endow materials with dynamic chiro-optical functionality, which can leverage of light to precisely control and manipulate the circularly polarized RTP properties with the remarkable advantages of being contactless, wireless and fatigue-resistant. Significantly, the distinct materials with dynamic properties can be used as anti-counterfeiting materials involving photoprogrammability.

Recent Advances in Organic Room Temperature Phosphorescence of Triphenylamine‐Based Doping Systems

AbstractThe host–guest doping strategy has become one of the most effective approaches to realize pure organic room temperature phosphorescence (RTP). Crystalline small molecules can provide a rigid environment that restricts the molecular motion of luminescent guests, thus enhancing phosphorescence emission. Triphenylamine (TPA) is a classic crystalline small molecule matrix that, when doped with designed guest molecules, enables tunable RTP properties and diverse functionalities. These properties afford TPA‐based doping systems with numerous applications in anticounterfeiting, bio‐imaging, and multiple responsive sensing. In this concept, design strategies, luminescence mechanisms, and applications of TPA‐based host‐guest doping systems are summarized. Moreover, the future prospects of TPA‐based RTP materials are proposed.

External Heavy-Atom Activated Phosphorescence of Organic Luminophores in a Rigid Fluid Matrix

Growing attention has been paid to pure organic room-temperature phosphorescence (RTP). Although an insufficient population and fast nonradiative decay of triplet excitons are avoided in recent endeavors, complicated synthesis and limited universality still hinder its development. Further, fluid RTP materials are more difficult to design because of faster nonradiative relaxation. Herein, a deep eutectic mixture of glucose and choline, a stable supercooled liquid at room temperature, is employed as a matrix. Direct transformation from commercial fluorescent dyes to RTP fluid is realized by doping without modifications. The excited triplet states are generated by an external heavy atom, while the rigid noncovalent network stabilizes them with both functions intrinsic to the liquid matrix. Modulation of matrix components also results in nearly white light emission of a single dye. This study presents a general strategy to design fluid RTP materials starting from the vast library of fluorophores.

Supramolecular Room Temperature Phosphorescent Materials Based on Cucurbit[8]uril for Dual Detection of Dodine.

In recent years, host-guest interactions of macrocycles have attracted much attention as an emerging method for enhancing the intersystem crossing of pure organic room-temperature phosphorescence. In this work, we utilize cucurbit[8]uril (Q[8]) to specifically recognize synthetic bromophenyl pyridine derivatives (BPCOOH) to construct a highly stable charge-transfer dimer, where the bromophenyl pyridine moiety of BPCOOH is encapsulated by Q[8] in a 1:2 host/guest ratio. The assemblies exhibit specific recognition and detection properties for dodine on both fluorescence and phosphorescence spectra. Subsequently, the solid films were prepared by introducing carboxymethylcellulose sodium into the assemblies, which greatly enhanced its RTP performance by increasing the noncovalent bonding interactions, enabling the visualization of high-strength RTP and quantitative testing of the solid state. Finally, this material was used for the application of portable indicator papers to achieve rapid and visualized detection of dodine in daily life, which provides more possibilities for the potential applications of cucurbit[n]uril-based room-temperature phosphorescence material.