Afterglow materials and methods of fabrication thereof

Abstract

The present disclosure concerns an afterglow material, comprising an amorphous matrix comprising a compound of Formula (I); 5 wherein X is selected from O and S; and R1, R2 and R3 are independently selected from optionally substituted alkyl, optionally substituted aryl, and optionally substituted heteroaryl; and a dopant homogenously dispersed within the amorphous matrix; wherein the dopant is at a % weight ratio of about 0.1% to about 10% relative to the amorphous matrix. The present disclosure also concerns a method of fabricating an 10 afterglow material.

Description

[0001] Afterglow Materials and Methods of Fabrication Thereof

[0002] Technical Field

[0003] The present invention relates, in general terms, to afterglow materials and their methods of fabrication thereof.

[0004] Background

[0005] Organic afterglow materials, capable of maintaining luminescence for over several tens of milliseconds or even seconds after the excitation ceases, have garnered significant attention in recent years due to their large Stokes shift, easy color tunability, high signal-to-noise ratio, and prolonged duration of emission. Due to unique luminescence properties, afterglow materials have been successively applied in fields such as multicolor display, encryption, bioimaging, and responsive sensors. To date, organic afterglow has been achieved by various strategies such as host-guest doping strategy, crystal-inducement, supramolecular assembly, co-crystallization, H-aggregation and others. However, developing materials that exhibit long-lasting, full-color afterglow across the entire spectrum from violet to near infrared while achieving high phosphorescence quantum yields remains challenging. Additionally, finding simple processing methods for new applications is still a hurdle in this field. While small molecules offer advantages like precise synthesis, easy purification, and batch-to-batch homogeneity, their tendency to crystallize and the weak intermolecular interactions hinder large-scale fabrication, long fiber production, and complex 3D structure formation. To enhance the processability of small molecules in practical applications, they have to be fabricated into uniform particles and then mixed with matrices such as aloe vera gel, UV curable resin. However, this approach increases the molecular surface area, making them more susceptible to environmental quenching from oxygen and moisture. On the other hand, disrupting the crystal lattice can reduce vibration suppression, potentially weakening the afterglow performance. Given these limitations, it is crucial to establish a versatile and easily accessible system with tunable afterglow properties and excellent processability to fully unlock the application potential of organic afterglow materials.

[0006] Host-guest systems are more likely to address both challenges simultaneously, as guests play a crucial role in fine-tuning emission color and brightness, and the host influences microenvironment rigidity, mechanical properties, and processability. For the host design, high triplet energy level is also expected to avoid energy back transfer from the guest after excitation. However, phase separation during doping, especially when dopant and host structures differ significantly, can lead to non-uniform films or even the failure to produce afterglow.

[0007] It would be desirable to overcome or ameliorate at least one of the above-described problems.

[0008] Summary

[0009] The present disclosure concerns an afterglow material, comprising:

[0010] a) an amorphous matrix comprising a compound of Formula (I):

[0011]

[0012] wherein

[0013] X is selected from 0 and S; and

[0014] Ri, R2 and Rs are independently selected from optionally substituted alkyl, optionally substituted aryl, and optionally substituted heteroaryl; and

[0015] b) a dopant homogenously dispersed within the amorphous matrix;

[0016] wherein the dopant is at a % weight ratio of about 0.1% to about 10% relative to the amorphous matrix.

[0017] In some embodiments, Ri, R2, and R3 are independently C1-C5 alkyl.

[0018] In some embodiments, the compound of Formula (I) is selected from:

[0019]

[0020] In some embodiments, the compound of Formula (I) is characterised by a melting temperature of about 140 °C to about 170 °C. In some embodiments, the compound of Formula (I) is characterised by a crystallisation temperature of about 40 °C to about 110 °C.

[0021] In some embodiments, the compound of Formula (I) is characterised by a glass transition temperature of about 20 °C to about 40 °C.

[0022] In some embodiments, the dopant exhibits luminescence upon excitation with electromagnetic radiation.

[0023] In some embodiments, the dopant comprises optionally substituted conjugated aryl or optionally substituted conjugated heteroaryl.

[0024] In some embodiments, the dopant is selected from coronene, tris(l-naphthyl) phosphine (TNpP), methyl 2-amino-3-methoxybenzoate (MAMOBZ), 2,6-dibromo-4,4-difluoro-l,3,5,7-tetramethyl-8-phenyl-4-bora-3a,4a-diaza-s-indacene (DiBrBDP), coumarin 1 (CM1), 7H-benzo[c]carbazole (7HBCz), 5 / 7-benzo[b]carbazole (5HBCz), 1,8-naphthalic anhydride (1,8-NA) and pyrene (Py), (diphenyl)(l-naphthyl)amine (NpDPA), 1-pyrene carboxylic acid (PCA or PyCOOH), l-(2-bromophenyl)-lHbenzo[f]indole (BrPhBd), Benzo[e]pyrene (BeP) and a combination thereof.

[0025] In some embodiments, the afterglow material is characterised by a weight ratio of compound of Formula (I) to dopant of about 1000: 1 to about 10:1.

[0026] In some embodiments, the afterglow material is characterised by a degree of crystallinity of less than 5%.

[0027] In some embodiments, the afterglow material is characterised by a luminescence wavelength of about 350 nm to about 1500 nm.

[0028] In some embodiments, the afterglow material is characterised by a luminescence lifetime of at least about 1 ms.

[0029] In some embodiments, the afterglow material is characterised by a luminescence decay lifetime of at least about 1 ms.

[0030] In some embodiments, the afterglow material is characterised by a photoluminescence quantum yield of about 5% to about 45% when excited by at about 365 nm. In some embodiments, the afterglow material is characterised by a non-radioactive decay rate of about 0.2 s-1to about 5 s-1.

[0031] In some embodiments, the afterglow material is characterised by a viscosity of about 0.1 x 105Pa-s to about 10 x 105Pa-s when heated to about 55 °C to about 65 °C.

[0032] In some embodiments, the afterglow material is formed in a mould or as a fibre with a diameter of about 50 pm to about 200 pm.

[0033] The present disclosure also concerns a method of fabricating an afterglow material as disclosed herein, comprising:

[0034] a) melting a compound of Formula (I) to form a molten liquid;

[0035] b) homogenously dispersing a dopant in the molten liquid;

[0036] c) supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20°C to about 100 °C to form a supercooled liquid; and

[0037] d) solidifying the supercooled liquid by further cooling the supercooled liquid to form the afterglow material.

[0038] In some embodiments, step a) is performed at a temperature of about 150 °C to about 180 °C.

[0039] In some embodiments, the molten liquid is characterised by a viscosity of about 0.01 Pa s to about 0.5 Pa s.

[0040] In some embodiments, step c) is performed at a cooling rate of about 10 °C / min to about 50 °C / min.

[0041] In some embodiments, step c) comprises supercooling the molten liquid to a temperature of about 70 °C to about 90 °C to form the supercooled liquid.

[0042] In some embodiments, the supercooled liquid is characterised by a viscosity of about 1 x 102Pa s to about 1 x 1011Pa s.

[0043] In some embodiments, step d) is performed at a cooling rate of about 10 °C / min to about 50 °C / min to an ambient temperature. In some embodiments, step d) comprises solidifying the supercooled material by hot-pressing the supercooled liquid into a mould or thermally drawing the supercooled liquid into a fibre.

[0044] The present disclosure also concerns an afterglow material as disclosed herein; wherein the amorphous matrix is formed by supercooling a molten liquid to a temperature above its glass transition temperature and from about 20°C to about 100 °C, the molten liquid comprising the compound of Formula (I) and the dopant.

[0045] Brief description of the drawings

[0046] Embodiments of the present invention will now be described, by way of non-limiting example, with reference to the drawings in which:

[0047] Figure 1. Glass properties of TTPO and TTPS, a) DSC curves of TTPO and TTPS, b) Viscous of TTPO supercool liquid under different temperature. Tgrepresents glass transition temperature, Tprepresents crystallisation temperature, and Tmrepresents melting temperature, c) Soften point of TTPS glass.

[0048] Figure 2. Intermolecular interactions in TTPO crystal and afterglow glass properties of different doping systems, a) Intermolecular interactions in TTPO crystal, a, b, and c refer to the three axial parameters in a crystal unit cell, b) Transmission of quartz substrate, blank TTPO glass and different doping systems, c) p-XRD of doping systems after excitation, d) Decay profiles of different doping systems. e,f,g, Spectra of different TPPO doping systems, e) 7HBCz@ TTPO (f) 1,8NA@ TTPO and (g) BrPhBd@TTPO. All spectra were collected under 365 nm excitation.

[0049] Figure 3. Afterglow properties of G@TTPS. a) Py@TTPS. b) BeP@TTPS. c) Cor@TTPS. d) Lifetime of different systems.

[0050] Figure 4. Processing demonstration, a) Large area preparation, b) Hot pressing, c) Thermal drawn. All materials were excited by 365 nm flashlight.

[0051] Figure 5. 1 meter long flexible TTPO fiber.

[0052] Figure 6. Process to reshape the glass to a simple airplane.

[0053] Figure 7. Glass forming cycle and glass design strategy, a) Illustration of glass forming and aging, (i). Melting (ii), vitrification (iii), molecule reorganization, b) O-methylation from TPPO to TTPO.

[0054] Figure 8. Glass property of TTPO. a) Synthetic route to TTPO. b) TTPO conformations, c) Kissinger analysis to determine morphology stability, d) Viscosity and deformation rate of melt liquid at 443 K and supercool liquid at 358 K.

[0055] Figure 9. Intermolecular interactions in TTPO crystal and afterglow glass properties of different doping systems, a) Intermolecular interactions in TTPO crystal, a, b, and c refer to the three axial parameters in a crystal unit cell, b) Transmission of the quartz substrate, blank TTPO glass, and different doping systems, c) p-XRD of doping systems after excitation, d) TNpP@TTPO in powder form and glassy form, e) Spectra of different TPPO doping systems, f) Commission Internationale de L'Eclairage (CIE) 1931 diagram of different TTPO doping systems, g) Lifetime of different doping systems. All spectra were collected under 365 nm excitation. Camera setting: ISO 800 (UV on), ISO 5000 (UV off).

[0056] Figure 10. Mechanism study of different doping systems, a) Photo of different doping systems, b) Comparison of afterglow properties between BrPhBd@TTPO and BrPhBd@PMMA. c) Singlet and triplet states of BrPhBd monomer (top) compared to the BrPhBd-TTPO pair (bottom), d) Jablonski diagram for proposed photophysical processes of doping systems. ISC: intersystem crossing, TTET: triplet-triplet energy transfer, IC: internal conversion.

[0057] Figure 11. Differential scanning calorimetry (DSC) measurement to determine the glass transition temperature (Tg), crystallization temperature (onset) (Tp) and melting point (Tm).

[0058] Figure 12. TGA curve of TTPO.

[0059] Figure 13. Absorption and fluorescence spectra of TPPO and TTPO in DCM at 298 K, and phosphorescence spectra of TPPO and TTPO powders at 77 K. Absorption and fluorescence spectra were collected under 254 nm excitation. [TPPO]= [TTPO] = 10“5M. Phosphorescence spectra were collected under 254 nm excitation.

[0060] Figure 14. The effect of vitrification on glass formation.

[0061] Figure 15. DSC curves of TTPO under N2 atmosphere at 20 K-min1cooling rate and different heating rate.

[0062] Figure 16. Photoluminescence (PL), delay spectra, and lifetime profile of TNpP@TTPO in glassy state and powder state (365 nm excitation).

[0063] Figure 17. Chemical structures of guests.

[0064] Figure 18. Fluorescence spectra of guests in DCM at room temperature (310 nm excitation, [c] = 10-5M).

[0065] Figure 19. Delay 8 ms spectra of guests in toluene at 77 K (365 nm excitation, [c] = IO’3M).

[0066] Figure 20. Absorption spectra of guests in DCM ([c] = IO-5M).

[0067] Figure 21. PL spectra of guest@TTPO doping system (365 nm excitation).

[0068] Figure 22. Delayed spectra (8 ms) of guest@TTPO doping system (365 nm excitation). Figure 23. Photoluminescence quantum yields (PLQYs) of guest@TTPO doping system (365 nm excitation).

[0069] Figure 24. Lifetime profiles of guest@TTPO doping system (365 nm excitation).

[0070] Figure 25. Power-dependent experiments of Py@TTPO system, a) Delay spectrum measured at 8 ms under varying excitation intensities, b) Logarithmic relationship between delayed fluorescence and excitation power intensity.

[0071] Figure 26. Delay spectra of guest@PMMA (365 nm excitation).

[0072] Figure 27. Singlet and triplet energy distribution of guests and host.

[0073] Figure 28. DFT and TDDFT calculation results by using B3LYP / 6-3 llg(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-de2-TZVP basic set. a) CMI monomer, b) CMI-TTPO pair (hydrogen atoms were omitted for clarity).

[0074] Figure 29. Selected hole-electron diagrams of the Ti, T2, T3 states of CMI-TTPO pair in optimized conformations. Electron-hole densities of T2 and T3 were localized on the TTPO component and Ti was on the guest.

[0075] Figure 30. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) MAMOBZ monomer, b) MAMOBZ-TTPO pair (hydrogen atoms were omitted for clarity).

[0076] Figure 31. Selected hole-electron diagrams of the Tl, T7 states of MAMOBZ and TTPO in pair optimized conformations. Electron-hole density of T7 was localized on the TTPO component and Tl was on the guest.

[0077] Figure 32. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) 7HBCz monomer, b) 7HBCz- TTPO pair (hydrogen atoms were omitted for clarity).

[0078] Figure 33. Selected hole-electron diagrams of the Tl, T4, T5 states of 7HBCz-TTPO in optimized pair conformations. Electron-hole densities of T4 and T5 were localized on the TTPO component and Tl was on the guest.

[0079] Figure 34. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) NpDPA monomer, b) NpDPA- TTPO pair (hydrogen atoms were omitted for clarity).

[0080] Figure 35. Selected hole-electron diagrams of theTi, T6, T7 states of NpDPA and TTPO in pair optimized conformations. Electron-hole densities of T6 and T7 were localized on the TTPO component and Tl was on the guest.

[0081] Figure 36. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) 1,8-NA monomer, b) 1,8-NA- TTPO pair (hydrogen atoms were omitted for clarity).

[0082] Figure 37. Selected hole-electron diagrams of the T 1, T8 states of 1,8-NA-TTPO in pair optimized conformations. Electron-hole densities of Tiand T8were localized on the TTPO component and Tl was on the guest.

[0083] Figure 38. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) BrPhBd monomer, b) BrPhBd- TTPO pair (hydrogen atoms were omitted for clarity).

[0084] Figure 39. Selected hole-electron diagrams of the Tl, T6, T7 states of BrPhBd -TTPO pair in optimized conformations. Electron-hole densities of T6 and T7 were localized on the TTPO component and Tl was on the guest.

[0085] Figure 40. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) 5HBCz monomer, b) 5HBCz- TTPO pair (hydrogen atoms were omitted for clarity).

[0086] Figure 41. Selected hole-electron diagrams of the T 1, T5 states of 5HBCz-TTPO in pair optimized conformations. Electron-hole density of T5 was localized on the TTPO component and Tl was on the guest.

[0087] Figure 42. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4using B3LYP functional and the DKH-def2-TZVP basic set. a) Py monomer, b) Py-TTPO pair (hydrogen atoms were omitted for clarity).

[0088] Figure 43. Selected hole-electron diagrams of the T 1, T5, T6 states of Py-TTPO in pair optimized conformations. Electron-hole densities of T5 and T6 were localized on the TTPO component and Tl was on the guest.

[0089] Figure 44. DFT and TDDFT calculation results by using B3LYP / 6- 311g(d) basis set. SOCME calculation results by ORCA 5.0.4 using B3LYP / G functional and the DKH2 DKH-def2-TZVP basic set. a) DiBrBDP monomer, b) DiBrBDP-TTPO pair (hydrogen atoms were omitted for clarity).

[0090] Figure 45. Procedure of hot pressing.

[0091] Detailed description

[0092] "Alkyl" refers to monovalent alkyl groups which may be straight chained or branched and preferably have from 1 to 10 carbon atoms or more preferably 1 to 6 carbon atoms. Examples of such alkyl groups include methyl, ethyl, n-propyl, / so-propyl, n-butyl, iso- butyl, n-hexyl, and the like.

[0093] "Aryl" refers to an unsaturated aromatic carbocyclic group having a single ring (eg. phenyl) or multiple condensed rings (eg. naphthyl or anthryl), preferably having from 6 to 14 carbon atoms. Examples of aryl groups include phenyl, naphthyl and the like.

[0094] "Heteroaryl" refers to a monovalent aromatic heterocyclic group which fulfils the Hiickel criteria for aromaticity (ie. contains 4n + 2 n electrons) and preferably has from 2 to 10 carbon atoms and 1 to 4 heteroatoms selected from oxygen, nitrogen, selenium, and sulfur within the ring (and includes oxides of sulfur, selenium and nitrogen). Such heteroaryl groups can have a single ring (eg. pyridyl, pyrrolyl or N-oxides thereof or furyl) or multiple condensed rings (eg. indolizinyl, benzoimidazolyl, coumarinyl, quinolinyl, isoquinolinyl or benzothienyl).

[0095] Examples of heteroaryl groups include, but are not limited to, oxazole, pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, indolizine, isoindole, indole, indazole, purine, isoquinoline, quinoline, phthalazine, naphthylpyridine, quinoxaline, quinazoline, cinnoline, pteridine, carbazole, carboline, phenanthridine, acridine, phenanthroline, isothiazole, phenazine, isoxazole, isothiazole, phenoxazine, phenothiazine, thiazole, thiadiazoles, oxadiazole, oxatriazole, tetrazole, thiophene, benzo[b]thiophene, triazole, imidazopyridine and the like.

[0096] In this specification "optionally substituted" is taken to mean that a group may or may not be further substituted or fused (so as to form a condensed polycyclic group) with one or more groups selected from hydroxyl, acyl, alkyl, alkoxy, alkenyl, alkenyloxy, alkynyl, alkynyloxy, amino, aminoacyl, thio, arylalkyl, arylalkoxy, aryl, aryloxy, carboxyl, acylamino, cyano, halogen, nitro, phosphono, sulfo, phosphorylamino, phosphinyl, heteroaryl, heteroarylalkyl, heteroaryloxy, heterocyclyl, heterocyclylalkyl, heterocyclyloxy, oxyacyl, oxime, oxime ether, hydrazone, oxyacylamino, oxysulfonylamino, aminoacyloxy, trihalomethyl, trialkylsilyl, pentafluoroethyl, trifluoromethoxy, difluoromethoxy, trifluoromethanethio, trifluoroethenyl, mono- and di-alkylamino, mono-and di-(substituted alkyl)amino, mono- and di-arylamino, mono- and di-heteroarylamino, mono- and di-heterocyclyl amino, and unsymmetric di-substituted amines having different substituents selected from alkyl, aryl, heteroaryl and heterocyclyl, and the like, and may also include a bond to a solid support material, (for example, substituted onto a polymer resin). For instance, an "optionally substituted amino" group may include amino acid and peptide residues.

[0097] Afterglow or persistent luminescence materials have garnered interest due to their ability to continue emitting light for an extended period after the excitation source has been removed. Afterglow materials are substances that absorb light and then release that energy as visible light over an extended period. The prolonged light emission may be due to electrons being excited by light into a higher energy state, followed by a return to the ground state with the release of energy as light. This prolonged light emission is valuable for a variety of applications, such as emergency signage, decorative lighting, and safety markers. Conventional afterglow materials, however, often suffer from limited luminance, short afterglow lifetimes, and poor colour tunability.

[0098] The present disclosure is predicated on the understanding that triphenylphosphine oxide (TPPO) has been used as an afterglow host due to its rigid tetrahedron structure and high triplet energy level. However, severe phase separation occurs in systems when the host and guest have significant structural differences.

[0099] Molecular glasses (MGs) are a type of organic small molecules that form an amorphous solid at room temperature and a viscous supercooled liquid between the glass transition temperature and the melting point, offering a promising solution for improving the dopant tolerance and processability of small molecular afterglow system (Figure 7a). From the structure perspective, MGs typically have irregular structures leading to multiple conformations which may help hinder the rearrangement of molecules, thereby reducing the crystal growth rate, and enabling the existence of a temperature dependent, processible viscous supercooled liquid state. An irregularly shaped molecule may provide a rigid environment and may serve as a processible glassy afterglow host.

[0100] The present disclosure concerns an afterglow material comprising an amorphous matrix comprising a compound of Formula (I) and a dopant. The compound of Formula (I) may be derived from phosphine oxide and / or sulfide moieties, which may be capable of forming an amorphous matrix. The combination of the compound of Formula (I) and dopant may enable high-efficiency afterglow emission with tunable colour, long persistence, and desirable optical and thermal properties. The afterglow material may exhibit persistent luminescence, or afterglow, following excitation by ultraviolet, visible, or other electromagnetic radiation. The afterglow material may be a type of molecular glass. Luminescence, such as fluorescence, phosphorescence, delayed fluorescence, other types of afterglow such as long persistent luminescence, may occur when a material emits light as excited electrons return to lower energy states. Without wishing to be bound by theory, when the afterglow material is excited with electromagnetic radiation, the dopant may absorb the energy and be in an excited state. The excited dopant may relax over time, releasing the energy absorbed as the excited dopant return to a ground state. This may result in a decay of luminescence as more dopant molecules within the amorphous matrix go from the excited state to the ground state through the release of energy via photons, also known as radiative decay. Energy may also be lost through non-radiative decay such as through heat and vibration. Some of the energy may also be captured by the amorphous matrix. The compound of Formula (I) may also provide a host lattice containing trap states capable of storing excitation energy, while the dopant may emit light during the gradual release of the stored energy. The compound of Formula (I) may also provide a host material capable of transferring their triplet energy to the dopant, while the dopant may emit light during the gradual release of the energy. The afterglow material described herein may be used in luminescent devices, display elements, emergency signage, anti-counterfeiting logo and other applications requiring persistent light emission after the removal of an excitation source, such as afterglow encryption and sensor applications.

[0101] Accordingly, the present disclosure concerns an afterglow material, comprising: a) an amorphous matrix comprising a compound of Formula (I):

[0102]

[0103] wherein

[0104] X is selected from 0 and S; and

[0105] Ri, R2 and Ra are independently selected from optionally substituted alkyl; optionally substituted aryl, optionally substituted heteroaryl; and

[0106] b) a dopant homogeneously dispersed within the amorphous matrix; wherein the dopant is at a % weight ratio of about 0.1% to about 10% relative to the amorphous matrix.

[0107] An amorphous material refers to a material that lacks long-range order and periodicity found in crystalline materials. The atoms, molecules, or structural units are arranged in a random, disordered manner, without a well-defined and repeating crystal lattice. An amorphous material may exhibit isotropic properties, meaning that the physical, chemical and optical properties may be the same in all directions, unlike the anisotropic nature of crystalline solids. An amorphous matrix refers to a host material having a disordered, non-crystalline structural arrangement in which other species, such as molecules, ions, dopants, may be embedded or dispersed. The amorphous matrix may have a small amount of short-range ordered forces, resulting in a small amount crystallinity. The small amount of crystallinity does not affect the long-range amorphous nature of the matrix. For example, the amount of crystallinity may be less than about 10%, less than about 5%, or less than about 1%. The amorphous matrix may have 0% crystallinity as shown in Fig. 2c and Fig. 9c where a broad band was observed for the afterglow material. This may result in a transparent material as there is little to no periodic lattice to coherently scatter or diffract light. The amorphous matrix may provide a rigid and uniform structure and may be mechanically stable and uniform on a macroscopic scale.

[0108] In contrast, a crystalline material refers to a solid with atoms, ions, or molecules arranged in a highly ordered, repeating three-dimensional pattern called a crystal lattice. The ordered structure gives crystalline materials distinct properties like sharp melting points and well-defined physical characteristics. The ordered structure is a long-range, periodic arrangement of the atoms, ions, or molecules and is formed by small repeating units, known as a unit cell. A crystalline material may be a polycrystalline material where it is made up of many small crystalline grains, each with the crystal structure but different orientations in space. The crystalline grains are separated by grain boundaries. The grain boundaries may scatter, refract or diffract light, resulting in the polycrystalline materials being opaque.

[0109] Without being bound by theory, the amorphous matrix of the afterglow material comprises the compound of Formula (I), which may serve as the host material. In its amorphous state, the compound of Formula (I) may not exhibit a regular, crystalline structure, but rather an irregular, disordered arrangement of the molecular units. This amorphous structure may be advantageous for the afterglow properties of the material. The matrix may provide a rigid and disordered environment. The dopant, present at a low concentration of about 0.1% to about 10% weight ratio to the matrix, may function as a luminescent activator and / or emitter. The dopant may be isolated from each other such that there is no self-quenching after excitation, and immobilised within the matrix such that the dopant may not easily move, rotate or collide but may be allowed to be excited to a higher energy state. In this regard, the surrounding molecules of the compound of Formula (I) may form a random, non-periodic coordination environment around each dopant molecule. When the afterglow material is irradiated with electromagnetic radiation, the compound of Formula (I) may be excited to generate triplet excitons through intermolecular crossing. The high energy triplet excitons may transfer their energy to the dopant molecules. The dopant molecules within the amorphous matrix may be directly excited by the electromagnetic radiation or through the gradual energy transfer from the host matrix. The rigid amorphous matrix may suppress non-radiative relaxation and may stabilize dopant triplet excitons, enabling radiative decay, such as phosphorescence, with long lifetimes, and hence afterglow.

[0110] The amorphous matrix may also provide a rigid environment that may suppress non-radiative pathways of the dopant in the release of energy. This may help to stabilise triplet excitons formed in the dopant. Triplet excitons may be excited electronic states where the electron and hole have parallel spins and may be formed when an electron is excited from ground state to an excited triplet state. The triplet excitons may be long-lived and may lead to luminescence, such as phosphorescence emission. In a rigid environment, the triplet excitons may be less likely to undergo non-radiative decay pathways, such as thermal relaxation or quenching. This may facilitate radiative recombination of the excitons, leading to luminescence from the dopant. The luminescence may be room-temperature phosphorescence.

[0111] The amorphous matrix may reduce the amount of vibration motion, reducing non-radiative energy loss. When the amorphous matrix is formed from vitrification, which is the rapid cooling of a molten liquid, dynamic quenching via molecular collisions or diffusion may be suppressed and vibrational motion decreased. This may result in longer luminescence lifetimes.

[0112] The disordered arrangement of the compound of Formula (I) in the amorphous matrix may create a network of trap states, which may be able to effectively store excitation energy. When the afterglow material is exposed to an energy source, such as ultraviolet (UV) light or electron beam irradiation, the trap states may capture and retain a portion of this energy. Over time, the stored energy may be gradually released from the traps, leading to the emission of light - the characteristic afterglow or persistent luminescence. As the stored energy is released from the traps in the host compound of Formula (I), the dopant may absorb this energy and emit photons, resulting in the observed afterglow emission. The dopant selected may determine the wavelength or colour of the afterglow light. The lack of long-range order and crystallinity in the amorphous matrix may allow for a more isotropic and homogeneous distribution of the trap states and the dopant, leading to efficient energy transfer and uniform light emission.

[0113] The compound of Formula (I) may also provide a host material capable of transferring their triplet energy to the dopant, while the dopant may emit light during the gradual release of the energy. When the amorphous matrix is exposed to an energy source, such as ultraviolet (UV) light or electron beam irradiation, the compound of Formula (I) may be excited to generate triplet excitons through intermolecular system crossing. The high energy triplet excitons may transfer their energy to the dopant, resulting in highly efficient afterglow emission. The amorphous matrix may help to stabilise the triplet excitons formed, preventing rapid non-radiative decay of the triplet excitons. This may allow the energy to be effectively transferred to the dopant. The transfer of the triplet energy to the dopant may occur over an extended period, leading to a delayed energy transfer and may enable a prolonged luminescence emission from the dopant.

[0114] The afterglow material may exhibit thermoplasticity. Thermoplasticity refers to the ability of a material to become soft and pliable when heated and then harden and maintain its shape when cooled. Thermoplastic materials may be repeatedly heated, formed, and cooled without undergoing permanent structural changes. This reversible deformation capability enables the afterglow material to be reprocessed, repaired, or recycled if needed. The thermoplastic nature of the material may allow it to be heated, softened, and then shaped or moulded into various forms, such as films, coatings, fibres, or 3D-printed structures. This enhanced processability may be beneficial for the fabrication and application of the afterglow material. It may also allow the afterglow material to be integrated into existing thermoplastic processing techniques, such as injection molding, extrusion, or 3D printing, expanding the potential for large-scale production and diverse applications.

[0115] In some embodiments, the compound of Formula (I) is:

[0116]

[0117] wherein

[0118] X is selected from 0 and S; and

[0119] Ri, 2 and R3 are independently selected from optionally substituted alkyl, optionally substituted aryl, and optionally substituted heteroaryl.

[0120] In some embodiments, X is selected from 0 and S. In some embodiments, X is 0. In some embodiments, X is S.

[0121] In some embodiments, Ri, R2 and R3 are independently selected from optionally substituted alkyl. In some embodiments, Ri, R2, and R3 are independently optionally substituted C1-C5 alkyl. In some embodiments, Ri, R2, and R are independently C1-C5 alkyl. In some embodiments, Ri, R2, and R are independently methyl, ethyl or propyl.

[0122] It was found that ortho substitution may make the compound of Formula (I) more sterically crowded than meta substitution, which may increase the rotational barrier and may favour glass formation. In contrast, para substitution may maintain molecular symmetry and reduce the number of possible conformations. The introduction of optionally substituted alkyl, optionally substituted aryl and / or optionally substituted heteroaryl at the ortho-position of the phenyl rings in the compound of Formula (I) may affect the molecular structure and properties compared to triphenylphosphine oxide (TPPO). This may disrupt the symmetry of the phenyl rings. In the unsubstituted TPPO, the three phenyl rings may be able to adopt a more planar, co-planar arrangement due to the symmetry of the molecule. The presence of optionally substituted alkyl, optionally substituted aryl and / or optionally substituted heteroaryl may introduce steric hindrance and disrupts the planar conformation. The symmetry disruption may lead to increased conformational diversity in the compound. The phenyl rings may exist in various twisted or tilted conformations to accommodate the optionally substituted alkyl, optionally substituted aryl and / or optionally substituted heteroaryl. This may contribute to the amorphous nature of the material, as the irregular, non-planar molecular arrangements may prevent the formation of a well-ordered, crystalline structure. The optionally substituted alkyl, optionally substituted aryl and / or optionally substituted heteroaryl may introduce additional motion barriers within the molecular structure. The rotation and movement of the phenyl rings may be hindered by the presence of the substituents, which may lead to a restriction on the overall molecular mobility. Heteroatoms on the optionally substituted heteroaryl may contribute to the stabilisation of the amorphous matrix via hydrogen bonding or dipole-dipole interactions. This restricted molecular movement may help to create a more rigid environment within the amorphous matrix comprising the compound of Formula (I). The rigid environment and less planar arrangement of the matrix may result in a gradual release of the excitation energy and hence the persistent luminescence after the removal of the excitation energy on the afterglow material. The amorphous matrix may provide a network of trap states and allow a homogeneous distribution of the dopant for efficient energy storage and light emission. The amorphous matrix may also provide a host material capable of transferring triplet energy from the compound of Formula (I) to the dopant, allowing a gradual release of energy from the dopant via prolonged luminescence.

[0123] The compound of Formula (I) may have a higher triplet energy level than that of the dopant. The energy level difference or bandgap may facilitate energy transfer from the compound of Formula (I) to the dopant. The energy level difference may be larger than 3.0 eV. The energy level difference may be larger than 3.5 eV, larger than 4.0 eV, larger than 4.5 eV, or larger than 5.0 eV. It may help prevent the back-transfer of energy from the dopant's triplet state to the compound of Formula (I), ensuring that the energy is channelled towards the radiative recombination in the dopant, leading to luminescence. The high triplet energy may help to stabilise triplet excitons formed in the dopant from excitation and may reduce non-radiative energy loss, further enhancing luminescence. This may also allow the compound of Formula (I) to serve as a host for various dopants as the energy level difference may be optimised to facilitate efficient energy transfer across various dopants.

[0124] In some embodiments, the compound of Formula (I) is selected from:

[0125]

[0126] The compound of Formula (I) may be characterised by a melting temperature, a crystallisation temperature and a glass transition temperature. A melting temperature is the temperature at which a crystalline structure in a material is destroyed and the crystalline material melts into a liquid. Crystallisation temperature is the temperature at which a substance in a liquid state begins to crystallise and form long range, ordered crystal structures. The crystallisation temperature represents the point at which the disordered, amorphous arrangement of the molecules starts to transition into a more organised, crystalline state. The glass transition temperature (Tg) is the temperature at which an amorphous solid, such as the compound of Formula (I) in the afterglow material, transitions from a hard, glassy state to a soft, rubbery state. The melting temperature is typically higher than the crystallisation temperature and the crystallisation temperature is typically higher than the glass transition temperature.

[0127] For an amorphous material, the material may soften when heated above the glass transition temperature. As the heating continues, crystallisation may occur at the crystallisation temperature as the molecules of the compound of Formula (I) rearrange themselves to form crystalline regions. When further heated, the crystalline regions may melt at the melting temperature.

[0128] The crystallisation temperature may define the temperature range in which the material may be processed and maintained in the desired amorphous state. If the material is cooled slowly to below its crystallisation temperature, it may begin to solidify and crystallise, which may make it harder to make into the desired form, such as a stamp or a fibre. By first melting the compound of Formula (I) and the dopant above the melting temperature and then rapidly cooling the molten liquid to a temperature either above or below the crystallisation temperature, but above the glass transition temperature, the material may form a supercooled liquid state as the material may not have enough time to undergo crystallisation. This rapid cooling to form a supercooled liquid is also known as supercooling. Supercooling is the process in which a liquid is cooled below its melting temperature without undergoing crystallisation. By further rapid cooling of the supercooled liquid to a temperature below its glass transition temperature, the supercooled liquid may solidify into an amorphous, glassy state as the molecules of the compound of Formula (I) may not have enough time to arrange into a crystal lattice. This amorphous structure provide a host material capable of transferring their triplet energy to the dopant, as well as for the homogeneous distribution of the dopant within the matrix.

[0129] Below the Tg, the material may exhibit characteristics of a rigid, solid-like material, while above the Tg, the material may become more flexible and mobile. This may affect the thermal stability and mechanical properties of the amorphous matrix. The Tgmay influence the processing and fabrication of the afterglow material. By maintaining the material above its Tgduring solidification, it may be more easily moulded, extruded, or deposited into the desired form, such as a powder, film, fibre or coating.

[0130] In some embodiments, the compound of Formula (I) is characterised by a melting temperature of about 140 °C to about 170 °C. In other embodiments, 140 °C to about 165 °C, about 140 °C to about 160 °C, about 140 °C to about 155 °C, about 140 °C to about 150 °C, about 150 °C to about 170 °C, about 150 °C to about 165 °C, about 150 °C to about 160 °C, about 150 °C to about 155 °C, about 155 °C to about 160 °C, about 160 °C to about 170 °C, about 160 °C to about 165 °C, or about 165 °C to about 170 °C. In some embodiments, the melting temperature is about 156 °C to about 165 °C. In some embodiments, the melting temperature is about 156 °C. In some embodiments, the melting temperature is about 165 °C.

[0131] In some embodiments, the compound of Formula (I) is characterised by a crystallisation temperature of about 40 °C to about 110 °C. In other embodiments, the crystallisation temperature is about 40 °C to about 100 °C, about 40 °C to about 90 °C, about 40 °C to about 80 °C, about 40 °C to about 90 °C, about 40 °C to about 60 °C, about 40 °C to about 50 °C, about 50 °C to about 110 °C, about 50 °C to about 100 °C, about 50 °C to about 90 °C, about 50 °C to about 80 °C, about 50 °C to about 70 °C, about 50 °C to about 60 °C, about 60 °C to about 110 °C, about 60 °C to about 100 °C, about 60 °C to about 90 °C, about 60 °C to about 80 °C, about 60 °C to about 70 °C, about 70 °C to about 110 °C, about 70 °C to about 100 °C, 70 °C to about 90 °C, about 70 °C to about 80 °C, about 80 °C to about 110 °C, about 80 °C to about 100 °C, about 80 °C to about 90 °C, about 90 °C to about 110 °C, about 90 °C to about 100 °C, or about 100 °C to about 110 °C. In some embodiments, the crystallisation temperature is about 50 °C to about 100 °C. In some embodiments, the crystallisation temperature is about 50 °C. In some embodiments, the crystallisation temperature is about 99 °C.

[0132] In some embodiments, the compound of Formula (I) is characterised by a glass transition temperature of about 20 °C to about 40 °C. In other embodiments, the glass transition temperature is about 20 °C to about 35 °C, about 20 °C to about 30 °C, about 20 °C to about 25 °C, about 25 °C to about 40 °C, about 25 °C to about 35 °C, about 25 °C to about 30 °C, about 30 °C to about 40 °C, about 30 °C to about 35 °C, or about 35 °C to about 40 °C. In some embodiments, the glass transition temperature is about 25 °C to about 32 °C. In some embodiments, the glass transition temperature is about 25 °C. In some embodiments the glass transition temperature is about 32 °C.

[0133] In some embodiments, the dopant exhibits luminescence upon excitation with electromagnetic radiation. When the afterglow material is exposed to an external energy source, such as UV light or other electromagnetic radiation, the dopant may be excited and become luminescent. The dopant may absorb the energy from the electromagnetic radiation, causing the dopant to transition from their ground state to an excited state. After being excited, the dopant may undergo radiative relaxation, where the dopant may emit photons (light) as the dopant return to the ground state configuration. The emitted photons from the dopant's radiative relaxation are the source of the afterglow luminescence observed in the material. The wavelength or colour of the afterglow emission may be due to the different dopants used. The efficiency and persistence of the afterglow emission may be influenced by factors such as the concentration of the dopant, its interaction with the host compound of Formula (I), and the presence of any energy transfer mechanisms between the host and the dopant.

[0134] In some embodiments, the dopant comprises optionally substituted conjugated aryl or optionally substituted conjugated heteroaryl. Aryl groups, such as phenyl, naphthyl, or other polycyclic aromatic rings, may provide a rigid, conjugated structure that may effectively participate in luminescent processes. The optionally substituted conjugated aryl or optionally substituted conjugated heteroaryl may result in a delocalization of pi-electrons throughout the aromatic ring system. The aromatic rings may be fused together, creating an extended, planar system of TT electrons that may be delocalised across multiple aromatic rings. This may form a fused system of electron rr-conjugation. The delocalized n-electron system of the aromatic rings may facilitate the absorption and emission of light. Electron-donating or electron-withdrawing groups may be introduced to modify the energy levels, emission wavelength, and luminescence efficiency of the dopant. The dopant may have a planar or rigid molecular structure. This rigidity may help restrict intramolecular motion and non-radiative decay pathways, thereby enhancing the luminescence quantum yield of the dopant. The dopant may be a polycyclic aromatic hydrocarbon (e.g., pyrene, perylene), aromatic heterocycle (e.g., carbazole, indole), and substituted aryl compound (e.g., arylamine, aryl carboxylic acids).

[0135] In some embodiments, the dopant is selected from coronene, tris( 1-naphthyl) phosphine (TNpP), methyl 2-amino-3-methoxybenzoate (MAMOBZ), 2,6-dibromo-4,4-difluoro-l,3,5,7-tetramethyl-8-phenyl-4-bora-3a,4a-diaza-s-indacene (DiBrBDP), coumarin 1 (CM1), 7H-benzo[c]carbazole (7HBCz), 5 / - / -benzo[b]carbazole (5HBCz), 1,8-naphthalic anhydride (1,8-NA) and pyrene (Py), (diphenyl)(l-naphthyl)amine (NpDPA), 1-pyrene carboxylic acid (PCA), l-(2-bromophenyl)-lHbenzo[f]indole (BrPhBd), Benzo[e]pyrene (BeP) and a combination thereof. In some embodiments, the dopant is selected from 7HBenzo[c]carbazole (7HBCz), l-(2-bromophenyl)-lHbenzo[f]indole (BrPhBd), 1,8-naphthalic anhydride (1,8-NA), pyrene (Py), Benzo[e]pyrene (BeP), coronene (Cor) and a combination thereof.

[0136] In some embodiments, the afterglow material is characterised by a dopant at a % weight ratio of about 0.1% to about 10% to the matrix. This may allow the dopant to be present in sufficient concentration to effectively contribute to the afterglow emission. Higher dopant concentrations may lead to concentration quenching, where the luminescence efficiency may be reduced due to increased non-radiative decay pathways or energy transfer between dopant molecules. A dopant present at a % weight ratio of about 0.1 wt% to about 10 wt% relative to the matrix may help avoid the concentration quenching effects, preserving the luminescence quantum yield of the dopant. This may also maintain the integrity and stability of the amorphous matrix. The balance of the amorphous matrix and the dopant concentration may contribute to the processability and durability of the afterglow material. The high amorphous matrix content may help to provide mechanical stability and allow the material to be readily fabricated into various forms, such as powders, films, fibres or coating, while the low dopant content may ensure efficient afterglow emission.

[0137] In other embodiments, the % weight ratio is about 0.1% to about 8%, about 0.1% to about 6%, about 0.1% to about 4%, about 0.1% to about 2%, about 0.1% to about 0.5%, about 0.5% to about 10%, about 0.5% to about 8%, 0.5% to about 6%, about 0.5% to about 4%, about 0.5% to about 2%, about 0.5% to about 1%, about 1% to about 10%, about 1% to about 8%, about 1% to about 6%, about 1% to about 4%, about 1% toa bout 2%, about 2% to about 10%, about 2% to about 8%, about 2% to about 6%, about 2% to about 4%, about 4% to about 10%, about 4% to about 8%, about 4% to about 6%, about 6% to about 10%, about 6% to about 8%, or about 8% to about 10%. relative to the matrix. In some embodiments, the % weight ratio is about 0.5% to about 2% relative to the matrix. In some embodiments, the % weight ratio is about 1% relative to the matrix.

[0138] In some embodiments, the afterglow material is characterised by a weight ratio of compound of Formula (I) to dopant of about 1000:1 to about 10:1. In other embodiments, the weight ratio is about 1000:1 to about 50:1, about 1000:1 to about 100:1, about 1000:1 to about 250:1, about 1000:1 to about 500:1, about 1000:1 to about 750:1, about 750:1 to about 10:1, about 750:1 to about 50:1, about 750:1 to about 100:1, about 750:1 toa bout 250:1, about 750:1 to about 500:1, about 500:1 to about 10:1, about 500:1 to about 50:1, about 500:1 to about 100:1, about 500:1 to about 250:1, about 250:1 to about 10:1, about 250:1 to about 50:1, about 250:1 to about 100:1, about 100:1 to about 10:1, about 100:1 to about 50:1, or about 50:1 to about 10:1. In some embodiments, the weight ratio is about 100:1. In some embodiments, the afterglow material is characterised by a degree of crystallinity of less than about 5%. The degree of crystallinity refers to the percentage of material that is in a crystalline form. The amorphous matrix of the afterglow material may comprise some crystalline regions. A high degree of crystallinity may cause the afterglow material to lose its transparency, thereby limiting its usability in optical devices and invisible anti-counterfeiting logo designs. Crystallinity may also induce phase separation, which may be one of the drawbacks in crystalline afterglow systems. In contrast, an amorphous matrix may provide a disordered and uniform microenvironment that may ensure well dispersion and compatibility of various structural dopants. The amorphous matrix may exhibit a glass transition temperature, and the behaviour may be similar as that of polymers and hence provide for excellent processability of the afterglow material. A lower degree of crystallinity may result in a more amorphous structure, which may allow for more homogeneous distribution of the dopant throughout the material. An afterglow material with a degree of crystallinity of less than 5% may remain transparent and hence be used in optical devices and invisible anti-counterfeiting logo designs.

[0139] In other embodiments, the degree of crystallinity is less than 4%, less than 3%, less than 2%, less than 1%, or less than 0.5%. In some embodiments, the degree of crystallinity is 0%. The afterglow material may be completely amorphous.

[0140] The afterglow material may exhibit thermoplasticity. The afterglow material may begin to soften when heated above the glass transition temperature and hence the material may be able to flow. At higher temperatures, for example, above the melting temperature, any crystalline regions may also melt, resulting in a full flow of the material, allowing the material to be soft and pliable. At temperatures between the glass transition temperature and melting temperature, the afterglow material may be more viscous, making it advantageous to process the afterglow material at this temperature range as compared to below the glass transition temperature or above the melting temperature. A higher viscosity may help the material maintain its shape and structural integrity during processing. A low viscosity material may be more prone to deformation or collapse when subjected to shaping forces. A more viscous material may also be easier to handle and manipulate as it may be less likely to flow or spread uncontrollably. This may be beneficial for processes such as moulding, 3D printing and fibre drawing.

[0141] In some embodiments, the afterglow material is characterised by a luminescence wavelength of about 350 nm to about 1500 nm. The luminescence wavelength may be dependent on the dopant incorporated into the amorphous matrix. Different dopants may emit luminescence at different wavelengths. For example, a 1,8-NA @ TTPO system and a 1,8-NA @ polystyrene may both exhibit a yellow luminescence at 540 nm. This may mean that the luminescence is due to the dopant and not the TTPO or polystyrene. The afterglow material may be engineered to emit light across a wide range of the ultraviolet, visible and near-infrared spectrum, allowing for tuning of the afterglow colour.

[0142] In other embodiments, the luminescence wavelength is about 350 nm to about 1200 nm, about 350 nm to about 1000 nm, about 350 nm to about 800 nm, about 350 nm to about 500 nm, about 500 nm to about 1500 nm, about 500 nm to about 1200 nm, about 500 nm to about 1000 nm, about 500 nm to about 800 nm, about 800 nm to about 1500 nm, about 800 nm to about 1200 nm, about 800 nm to about 1000 nm, about 1000 nm to about 1500 nm, about 1000 nm to about 1200 nm, or about 1200 nm to about 1500 nm.

[0143] In some embodiments, the afterglow material is characterised by a luminescence lifetime of at least about 1 ms. A luminescence lifetime refers to the time required for the emission intensity of a luminescent system to decay to 1 / e (approximately 36.8%) of its initial value as the system relaxes from the excited state to the ground state. The luminescence lifetime may be longer than about 1 ms. An afterglow lifetime longer than 1 ms may provide a suitable duration of light emission for various applications, such as emergency signage, decorative lighting, and safety markers. This range may ensure that the afterglow material continues to emit light for an amount of time after the initial excitation, making it useful in real-world scenarios. A luminescence lifetime longer than about 1 ms may allow the afterglow to be perceived by the human eye, providing a visually noticeable and useful afterglow effect. The long lifetime of at least about 1 ms may allow the afterglow material to be tailored for different applications. Shorter lifetimes may be suitable for fast-response indicators, while longer lifetimes are beneficial for long-lasting safety and decorative lighting applications.

[0144] In other embodiments, the luminescence lifetime is at least about 5 ms, at least about 10 ms, at least about 50 ms, at least about 100 ms, at least about 250 ms, at least about 500 ms, at least about 750 ms, at least about 1000 ms, at least about 1250 ms, at least about 1500 ms, or at least about 1750 ms. In some embodiments, the luminescence lifetime is longer than about 1 ms. In some embodiments, the luminescence lifetime is at least about 3 ms. In some embodiments, the luminescence lifetime is at least about 1695 ms.

[0145] In some embodiments, the luminescence wavelength and / or lifetime of the dopant is substantially the same as when it is doped in the amorphous matrix.

[0146] In some embodiments, the afterglow material is characterised by a luminescence decay lifetime of at least about 1 ms. A luminescence decay lifetime refers to how the luminescence intensity decreases after the excitation is stopped or removed. A longer decay lifetime may correspond to a slower rate of luminescence intensity decrease, resulting in a more persistent and prolonged afterglow effect. The luminescence decay lifetime may be influenced by the compound of Formula (I). The compound of Formula (I) may affect the stability and lifetime of the excited dopants. The processing conditions and parameters for fabricating the afterglow material may also affect the luminescence decay lifetime. The cooling rates used, solidification methods, dopant concentrations may influence the formation and stabilisation of trap states, the energy transfer between the host and the dopant, the formation of the amorphous matrix and hence the luminescence decay lifetime. In some embodiments, the luminescence decay lifetime is more than about 1 ms. In some embodiments, the luminescence decay lifetime is more than 1 ms. In some embodiments, the luminescence decay lifetime of the afterglow material is the luminescence lifetime of the afterglow material.

[0147] In other embodiments, the luminescence decay lifetime is at least about 5 ms, at least about 10 ms, at least about 50 ms, at least about 100 ms, at least about 250 ms, at least about 500 ms, at least about 750 ms, at least about 1000 ms, at least about 1250 ms, at least about 1500 ms, or at least about 1750 ms.

[0148] In some embodiments, the afterglow material is characterised by a photoluminescence quantum yield of about 5% to about 45% when excited by at about 365 nm. Photoluminescence quantum yield is a measure of the efficiency of a luminescence material or afterglow material in converting absorbed photons into emitted photons. It may be defined as the ratio of the number of photons emitted by the material to the number of photons absorbed by the afterglow material. When the afterglow material is excited at a wavelength of about 365 nm, the afterglow material may be able to convert between about 5% to about 45% of the absorbed 365 nm photons into emitted photons, resulting in luminescence. A higher percentage may result in a brighter and more intense luminescence. In other embodiments, the photoluminescence quantum yield is about 5% to about 40%, about 5% to about 30%, about 5% to about 20%, about 5% to about 10%, about 10% to about 45%, abut 10% to about 40%, about 10% to about 30%, about 10% to about 20%, about 20% to about 45%, about 20% to about 40%, about 20% to about 30%, about 30% to about 45%, about 30% to about 40%, or about 40% to about 45% when excited at about 365 nm. In some embodiments, the photoluminescence quantum yield is about 9% to about 40%.

[0149] In some embodiments, the afterglow material is characterised by a non-radioactive decay rate of about 0.2 s1to about 5 s1. A non-radioactive decay rate (knr) refers the rate at which the excited luminescent species, such as the dopant, in the afterglow material return to the ground state through non-radioactive pathways. These non-radiative pathways do not involve the emission of a photon, and the energy may be dissipated through other mechanisms, such as thermal vibrations or energy transfer to the surrounding matrix. A lower non-radiative decay rate is preferred, as it may suggest a higher radiative decay rate and, consequently, a higher photoluminescence quantum yield (PLQY) for the afterglow material.

[0150] In other embodiments, the non-radioactive decay rate is about 0.2 s’1to about 4 s’1, about 0.2 s’1to about 3 s1, about 0.2 s1to about 2 s1, about 0.2 s1to about 1 s1, about 0.2 s1to about 0.5 s1, about 0.5 s1to about 5 s1, about 0.5 s1to about 4 s1, about 0.5 s'1to about 3 s’1, about 0.5 s'1to about 2 s’1, about 0.5 s'1to about 1 s’1, about 1 s'1to about 5 s’1, about 1 s'1to about 4 s’1, about 1 s'1to about 3 s’1, about 1 s'1to about 2 s'1, about 2 s'1to about 5 s’1, about 2 s'1to about 4 s’1, about 2 s'1to about 3 s’1, about 3 s'1to about 5 s’1, about 3 s’1to about 4 s’1, or about 4 s'1to about 5 s’1. In some embodiments, the non-radioactive decay rate is about 0.58 s’1to about 3.95 s1.

[0151] In some embodiments, the afterglow material is characterised by a viscosity of about 0.1 x 105Pa-s to about 10 x 105Pa-s when heated to about 55 °C to about 65 °C. The viscosity of the afterglow material may allow for processing and shaping of the afterglow material into a desired shape. In other embodiments, the viscosity is about 0.1 x 105Pa-s to about 8 x 105Pa-s, about 0.1 x 105Pa-s to about 5 x 105Pa-s, about 0.1 x 105Pa-s to about 3 x 105Pa-s, about 0.1 x 105Pa-s to about 1 x 105Pa-s, about 1 x 105Pa-s to about 10 x 105Pa-s, about 1 x 105Pa-s to about 8 x 105Pa-s, about 1 x 105Pa-s to about 5 x 105Pa-s, about 1 x 105Pa-s to about 3 x 105Pa-s, about 3 x 105Pa-s to about 10 x 105Pa-s, about 3 x 105Pa-s to about 8 x 105Pa-s, about 3 x 105Pa-s to about 5 x 105Pa-s, about 5 x 105Pa-s to about 10 x 105Pa-s, about 5 x 105Pa-s to about 8 x 105Pa-s, or about 8 x 105Pa-s to about 10 x 105Pa-s when heated to about 55 °C to about 65 °C. In some embodiments, the viscosity is about 1 x 105Pa-s when heated to about 55 °C to about 65 °C.

[0152] The afterglow material may be hot-pressed into a stamp, thermal drawn into a fibre or cast into a mould to form various 3D shapes.

[0153] In some embodiments, the afterglow material is formed in a mould or as a fibre with a diameter of about 50 pm to about 200 pm. In some embodiments, the afterglow material is formed in a mould. In some embodiments, the afterglow material is formed as a fibre with a diameter of about 50 pm to about 200 pm. In other embodiments, the diameter is about 50 pm to about 150 pm, about 50 pm to about 100 pm, about 100 pm to about 200 pm, about 100 pm to about 150 pm, or about 150 pm to about 200 pm.

[0154] In some embodiments, the afterglow material is formed as a fibre with a diameter of about 50 pm to about 200 pm and a length of about 0.3 m long to about 1.5 m long. Due to the isotropic and uniform nature of glass, weak and dispersive interactions may be distributed evenly in three orthogonal directions, therefore fibers may demonstrate flexibility and mechanical strength. A coiled fibre may be stretched into a straight configuration, and a 0.5 mg fibre may support weights of up to 500 mg without breaking. The fabrication of long and flexible fibres may enhance the development of innovative wearable devices, especially in applications such as intelligent textile sensors and optical devices, including fibre lasers and optical waveguide.

[0155] The fibre may be about 0.3 m long to about 1.2 m long, about 0.3 m long to about 1 m long, about 0.3 m long to about 0.8 m long, about 0.3 m long to about 0.5 m long, about 0.5 m long to about 1.5 m long, about 0.5 m long to about 1.2 m long, about 0.5 m long to about 1 m long, about 0.5 m long to about 0.8 m long, about 0.8 m long to 1.5 m long, about 0.8 m long to 1.2 m long, about 0.8 m long to 1 m long, about 1 m long to 1.5 m long, about 1 m long to about 1.2 m long, or about 1.2 m long to about 1.5 m long. In some embodiments, the fibre is about 0.5 m long to about 1 m long. In some embodiments, the fibre is about 0.5 m long. In some embodiments, the fibre is about 1 m long.

[0156] The present disclosure also concerns a method of fabricating an afterglow material as disclosed herein, comprising: a) melting a compound of Formula (I) to form a molten liquid;

[0157] b) homogenously dispersing a dopant in the molten liquid;

[0158] c) supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20°C to about 100 °C to form a supercooled liquid; and

[0159] d) solidifying the supercooled liquid by further cooling the supercooled liquid to form the afterglow material.

[0160] The melting of the powder of a compound of Formula (I) and a dopant may allow the dopant to be homogeneously dissolved in the melting powder to form a molten liquid. This may help to ensure a uniform and consistent distribution of the dopant throughout the amorphous matrix, enabling a uniform optical property throughout the afterglow material. This may minimise the risk of localised variations in colour, intensity, or emission characteristics, resulting in a more predictable and reliable afterglow performance. The homogeneous dissolution of the dopant in the molten liquid may facilitate the subsequent solidification of the afterglow material. The uniform composition and viscosity of the molten liquid may enable better control over the shaping, casting, or other fabrication techniques used to produce the final afterglow material.

[0161] In some embodiments, step a) is performed at a temperature of about 150 °C to about 180 °C. The temperature is about at least higher than the melting temperature of the compound of Formula (I). The temperature may be higher than the melting temperature of the compound of Formula (I) and low enough to ensure that the dopant does not decompose during the melting process. In other embodiments, the temperature is about 150 °C to about 170 °C, about 150 °C to about 160 °C, about 160 °C to about 180 °C, about 160 °C to about 170 °C, or about 170 °C to about 180 °C. In some embodiments, the temperature is about 170 °C.

[0162] In some embodiments, step b) comprises homogenously dispersing a dopant in the molten liquid. The dopant molecules may be evenly distributed throughout the molten liquid, avoiding the formation of localised high-concentration regions of dopant molecules, which may lead to concentration quenching and reduced luminescence. An even distribution of the dopant molecules in the molten liquid may enable efficient energy transfer from the amorphous matrix to the dopant when the molten liquid solidifies. In some embodiments, step a) and step b) are performed as a single step.

[0163] In some embodiments, the molten liquid is characterised by a viscosity of about 0.01 Pa s to about 0.5 Pa s. A low-viscosity molten liquid may be less prone to the formation of processing defects, such as air bubbles, uneven distribution, or surface irregularities, during the fabrication process. This may help to maintain the structural integrity and optical quality of the final afterglow material. The low viscosity of the molten liquid may also allow for faster heat transfer and more efficient solidification when the molten liquid is cooled. This may lead to shorter processing times and improved productivity during the manufacturing of the afterglow material.

[0164] In other embodiments, the viscosity is about 0.01 Pa s to about 0.3 Pa s, about 0.01 Pa s to about 0.1 Pa s, about 0.01 Pa s to about 0.08 Pa s, about 0.01 Pa s to about 0.05 Pa s, about 0.05 Pa s to about 0.5 Pa s, about 0.05 Pa s to about 0.3 Pa s, about 0.05 Pa s to about 0.1 Pa s, about 0.05 Pa s to about 0.08 Pa s, about 0.08 Pa s to about 0.5 Pa s, about 0.08 Pa s to about 0.3 Pa s, about 0.08 Pa s to about 0.1 Pa s, about 0.1 Pa s to about 0.5 Pa s, about 0.1 Pa s to about 0.3 Pa s, or about 0.3 Pa s to about 0.5 Pa s. In some embodiments, the viscosity is about 0.03 Pa s.

[0165] In some embodiments, the molten liquid is characterised by a viscosity of about 0.01 Pa s to about 0.5 Pa s at about 170 °C when a shear deformation is applied at a rate of about 25 s'1to about 35 s'1to the molten liquid. In other embodiments, the viscosity is about 0.01 Pa s to about 0.3 Pa s, about 0.01 Pa s to about 0.1 Pa s, about 0.01 Pa s to about 0.08 Pa s, about 0.01 Pa s to about 0.05 Pa s, about 0.05 Pa s to about 0.5 Pa s, about 0.05 Pa s to about 0.3 Pa s, about 0.05 Pa s to about 0.1 Pa s, about 0.05 Pa s to about 0.08 Pa s, about 0.08 Pa s to about 0.5 Pa s, about 0.08 Pa s to about 0.3 Pa s, about 0.08 Pa s to about 0.1 Pa s, about 0.1 Pa s to about 0.5 Pa s, about 0.1 Pa s to about 0.3 Pa s, or about 0.3 Pa s to about 0.5 Pa s when a shear deformation is applied at a rate of about 25 s'1to about 35 s’1, about 25 s'1to about 32 s’1, about 25 s'1to about 30 s1, about 25 s'1to about 28 s1, about 28 s-1to about 35 s1, about 28 s1to about 32 s1, about 28 s1to about 30 s'1, about 30 s1to about 35 s1, about 30 s1to about 32 s'1, or about 32 s'1to about 35 s'1to the molten liquid. In some embodiments, the viscosity is about 0.03 Pa s at about 170 °C when a shear deformation is applied at a rate of about 30 s'1to the molten liquid.

[0166] In some embodiments, step c) comprises supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20°C to about 100 °C to form a supercooled liquid and step d) solidifying the supercooled liquid by further cooling the supercooled liquid to form the afterglow material. The process may be known as vitrification. Vitrification is a process of transforming a material from a liquid into a non-crystalline, amorphous solid state without crystallisation. Supercooling is the process in which a liquid is cooled below its melting temperature without undergoing crystallisation. The liquid may remain in a metastable liquid state down to the crystallisation temperature or below the crystallisation temperature, until the liquid crystallises or is further cooled below or near the glass transition temperature to form an amorphous solid. By supercooling the molten liquid to room temperature, a uniform and transparent material may be produced. In contrast, allowing the molten liquid to cool naturally may result in the formation of a crystalline structure (Fig. 14). When the molten liquid is supercooled, the molecular motion of the compound of Formula (I) and the dopant may be restricted and the molecules may be immobilised. In a liquid or flexible matrix, excited states may lose energy through vibrational coupling and non-radiative decay. Upon vitrification, these vibrational and collisional pathways may be suppressed, and may result in the radiative processes dominating and thus a longer luminescence lifetime and higher quantum yield.

[0167] In some embodiments, step c) comprises supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20°C to about 100 °C to form a supercooled liquid. The molten liquid may be supercooled to a temperature above its glass transition temperature but below its crystallisation temperature to form a supercooled liquid. For example, TTPS and a dopant may be melted at about 170 °C and rapidly cooled to about 80 °C, which is below the crystallisation temperature of TTPS of about 99 °C and above the glass transition temperature of about 32 °C, to form a supercooled liquid. The supercooled liquid may then be rapidly cooled to ambient temperature to form an amorphous afterglow material with an amorphous matrix of TTPS. The molten liquid may be supercooled to a temperature above its crystallisation temperature and thus above its glass transition temperature to form a supercooled liquid. For example, TTPO and a dopant may be melted at about 170 °C and rapidly cooled to about 80 °C, which is above the crystallisation temperature of TTPO of about 50 °C and glass transition temperature of about 25 °C, to form a supercooled liquid. The supercooled liquid may then be rapidly cooled to ambient temperature to form an amorphous afterglow material with an amorphous matrix of TTPO.

[0168] The molten liquid may be cooled to a temperature which may be suitable for handling or processing for different applications to form a supercooled liquid. The supercooled liquid may be poured into a mould to form a stamp, or drawn to form a fibre. A balance between viscosity and temperature of the supercooled liquid may be obtained such that the supercooled liquid may be easily handled, shaped and fabricated into the desired form of the afterglow material, without compromising its structural integrity or requiring excessive heat that may be challenging to manage. The temperature may be about 70 °C to about 90 °C and the viscosity of the supercooled liquid may be about 1 x 102Pa-s to about 1 x 1011Pa-s. In some embodiments, the temperature is about 80 °C and the supercooled liquid is characterised by a viscosity of about 1 x 102Pa s to about 1 x 103Pa s. This may allow the supercooled liquid to be moulded to form a stamp or drawn to form a fibre.

[0169] In other embodiments, step c) comprises supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20 °C to about 80 °C, about 20 °C to about 60 °C, about 20 °C to about 40 °C, about 40 °C to about 100 °C, about 40 °C to about 80 °C, about 40 °C to about 60 °C, about 60 °C to about 100 °C, about 60 °C to about 80 °C, or about 80 °C to about 100 °C to form a supercooled liquid.

[0170] In some embodiments, step c) is performed at a cooling rate of about 10 °C / min to about 50 °C / min. By tuning the cooling rate, supercooling may be achieved. If the cooling rate is sufficiently fast, molecules of the compound of Formula (I) in different conformations may be frozen into the solid state which may prevent crystallisation and enable supercooling. In other embodiments, the cooling rate is about 10 °C / min to about 40 °C / min, about 10 °C / min to about 30 °C / min, about 10 °C / min to about 20 °C / min, about 20 °C / min to about 50 °C / min, about 20 °C / min to about 40 °C / min, about 20 °C / min to about 30 °C / min, about 30 °C / min to about 50 °C / min, about 30 °C / min to about 40 °C / min, or about 40 °C / min to about 50 °C / min.

[0171] In some embodiments, step c) comprises supercooling the molten liquid to a temperature of about 70 °C to about 90 °C to form the supercooled liquid. The temperature may be above the glass transition temperature of the compound of Formula (I). The temperature may be between the crystallisation temperature and the glass transition temperature of the compound of Formula (I) or may be above the crystallisation temperature of the compound of Formula (I). The supercooling may prevent the supercooled liquid from crystallising and maintaining a metastable noncrystalline state. A supercooled liquid may have higher viscosity compared to the molten liquid, which may aid in maintaining shape and structure of the supercooled material in step c).

[0172] In other embodiments, the temperature is about 70 °C to about 85 °C, about 70 °C to about 80 °C, about 70 °C to about 75 °C, about 75 °C to about 90 °C, about 75 °C to about 85 °C, about 75 °C to about 80 °C, about 80 °C to about 90 °C, about 80 °C to about 85 °C, or about 85 °C to about 90 °C. In some embodiments, the temperature is about 80 °C.

[0173] In some embodiments, the supercooled liquid is characterised by a viscosity of about 1 x 102Pa s to about 1 x 1011Pa s. The supercooled liquid may gradually become more and more viscous until it solidifies completely. The presence of a viscous supercooled liquid may allow a processing method like that used for inorganic glass, such as hot-pressing or thermal drawing.

[0174] In other embodiments, the viscosity is about 1 x 102Pa s to about 1 x 1010Pa s, about 1 x 102Pa s to about 1 x 108Pa s, about 1 x 102Pa s to about 1 x 105Pa s, about 1 x 105Pa s to about 1 x 1011Pa s, about 1 x 105Pa s to about 1 x 1010Pa s, about 1 x 105Pa s to about 1 x 108Pa s, about 1 x 10sPa s to about 1 x 1011Pa s, about 1 x 10sPa s to about 1 x 1010Pa s, or about 1 x 1010Pa s to about 1 x 1011Pa s. In some embodiments, the viscosity is about 1 x 102Pa s to about 1 x 103Pa s.

[0175] In some embodiments, step c) further comprises maintaining the supercooled liquid at to a temperature of about 70 °C to about 90 °C for at least about 0.5 minute. This may allow the supercooled liquid to reach a more homogenous and equilibrated state, ensuring a uniform distribution of the dopant within the supercooled liquid. In other embodiments, step c) further comprises maintaining the supercooled liquid at to a temperature of about 70 °C to about 85 °C, about 70 °C to about 80 °C, about 70 °C to about 75 °C, about 75 °C to about 90 °C, about 75 °C to about 85 °C, about 75 °C to about 80 °C, about 80 °C to about 90 °C, about 80 °C to about 85 °C, or about 85 °C to about 90 °C for at least about 1 minute, at least about 5 minutes, at least about 10 minutes, at least about 15 minutes, at least about 20 minutes, at least about 25 minutes, or at least about 30 minutes. In some embodiments, step c) further comprises maintaining the supercooled liquid at to a temperature of about 80 °C for about 0.5 minute to about 1 minute. In some embodiments, step c) further comprises maintaining the supercooled liquid at to a temperature of about 80 °C for at least about 30 minutes.

[0176] In some embodiments, step d) comprises solidifying the supercooled liquid by further cooling the supercooled liquid to ambient temperature to form the afterglow material. The ambient temperature may be about 20 °C to about 30 °C. The supercooled liquid may be cooled to a temperature near or lower than the glass transition temperature of the compound of Formula (I), such as about 20 °C to about 30 °C. This may allow the supercooled liquid to solidify while preserving the amorphous matrix structure of the afterglow material. This may result in a more thermally and mechanically stable amorphous solid afterglow material, which may benefit long-term performance and durability of the afterglow material.

[0177] In some embodiments, step d) is performed at a cooling rate of about 10 °C / min to about 50 °C / min to an ambient temperature. The supercooled liquid may solidify into a stable, amorphous solid matrix as the molecules of the compound of Formula (I) may not have time to arrange into a crystal lattice. In other embodiments, the cooling rate is about 10 °C / min to about 40 °C / min, about 10 °C / min to about 30 °C / min, about 10 °C / min to about 20 °C / min, about 20 °C / min to about 50 °C / min, about 20 °C / min to about 40 °C / min, about 20 °C / min to about 30 °C / min, about 30 °C / min to about 50 °C / min, about 30 °C / min to about 40 °C / min, or about 40 °C / min to about 50 °C / min to an ambient temperature. In some embodiments, step d) is performed at a cooling rate of about 10 °C / min to about 50 °C / min to a temperature of about 20 °C to about 30 °C.

[0178] In some embodiments, step d) comprises solidifying the supercooled material by hot-pressing the supercooled liquid into a mould or thermally drawing the supercooled liquid into a fiber. Hot-pressing may involve the use of a heated mould or die to compress and solidify the supercooled liquid. The afterglow may be a 3D object such as a stamp. Thermal drawing may involve drawing or extruding the supercooled liquid into the desired shape. The afterglow material may be a fibre.

[0179] The present disclosure also concerns an afterglow material as disclosed herein; wherein the amorphous matrix is formed by supercooling a molten liquid to a temperature above its glass transition temperature and from about 20°C to about 100 °C, the molten liquid comprising the compound of Formula (I) and the dopant.

[0180] Examples

[0181] The inventors have developed a method to create highly processable afterglow glass using our specifically designed molecules. Tri(2-methylphenyl) phosphine oxide (TTPO) and tri(2-methylphenyl) phosphine sulfide (TTPS) were designed as the afterglow glass hosts. By doping multiple molecules (referred to as G or guest) with these hosts using a melt-rapid cooling method at a 1 % weight ratio, uniform and transparent glass films (G@TTPO or G@TTPS) were formed. After just 10 seconds of photoactivation with a 50W, 365 nm torchlight, these glass films exhibited different afterglow durations and colors, depending on the dopants used. Notably, due to the slow crystallization rates of TTPO and TTPS, these glass systems exhibit temperature-dependent viscosity, allowing them to exist as viscous supercooled liquids and display thermoplasticity. These properties enable a variety of processing methods, including thermal drawing, hot pressing, cutting, and sticking for processing the afterglow materials. As a result, large-area transparent glass, stamps, and meter-scale fibers may be fabricated while retaining their afterglow properties. At last, the ease of processing may facilitate the development of complex and precise devices for afterglow encryption, display, and sensor applications.

[0182] Organic afterglow materials, known for their unique luminescent properties and diverse applications, have garnered significant attention in recent years. However, developing long-lasting, high-efficiency, full-color afterglow systems and exploring simple materials processing strategies for new applications are still challenging in this field. Herein, the inventors have rationally design a processable molecular glass and employ it as a host in a host-guest strategy to address these challenges. By strategically modifying the host via othyl-methylation, the inventors successfully create a molecular glass and capture its temperature-dependent, processable viscous supercooled liquid state. High-efficiency full color from violet to near-infrared afterglow systems with ultralong lifetimes are developed by doping varied structural dopants. The underlying glassforming and afterglow mechanisms are also clearly elucidated and verified. Moreover, the excellent glass-forming ability of the host and its viscous supercooled liquid enabled the glass system for large-area fabrication, shaping of objects with diverse 3D structures, and creation of flexible, meter-long afterglow fibers. This work offers significant potential for practical applications in advanced textiles, displays, and other fields.

[0183] Introduction

[0184] Triphenylphosphine oxide (TPPO) has been used as an afterglow host due to its rigid tetrahedron structure and high triplet energy level. However, severe phase separation occurs in systems when the host and guest have significant structural differences. By introducing three methyl groups to disrupt the symmetry of the phenyl group, the inventors developed a new host molecule, tri(2-methylphenyl) phosphine oxide (TTPO), which retains the strong afterglow performance of TPPO while significantly slowing down the

[0185] 70 crystallization rate and exhibiting temperature-dependent viscous supercooled liquid behavior (Fig. 7b). TTPO MG could be easily prepared on a hundred-gram scale (Fig.

[0186] 8a). Dopants at 1 wt% with various structures were uniformly dispersed, producing fullcolor afterglow with maximum emissions ranging from 410 to 767 nm and lifetimes varying from 3 to 1695 ms. The glass-forming ability of TTPO allows for large-area preparation and the presence of viscous supercool liquid endows us opportunities to process the glass system in a manner like inorganic glass. Objects with diverse 3D structures can be easily shaped by processing the viscous supercooled liquid. Additionally, for the first time, flexible meter-long afterglow fibers have been successfully fabricated from the small MGs. This work presents a valuable strategy for developing organic afterglow materials with excellent processability, offering significant potential for practical applications in wearable devices, smart displays, flexible electronics, and other fields.

[0187] Some advantages of the afterglow material include:

[0188] Low price and easily accessible: Most glass afterglow hosts have complex structures, requiring multiple steps and significant time for synthesis and scaling. TTPO and TTPS may be prepared from tri(2-methylphenyl) phosphine using hydroperoxide or sulfur as oxidants, at a scale of hundreds of grams. Additionally, TTPO and TTPS are considered industrial chemical byproducts, which may be collected from various useful reactions. This not only makes TTPO and TTPS cost-effective but also promotes the reuse of chemical waste.

[0189] For afterglow dopants: A 1% weight ratio dopant was used to prepare the afterglow molecular glass. Compounds such as 7HBenzo[c]carbazole (7HBCz), l-(2-bromophenyl)-lHbenzo[f]indole (BrPhBd), 1,8-naphthalic anhydride (1,8-NA), pyrene (Py), Benzo[e]pyrene (BeP) and coronene (Cor) have been tested to show very good results.

[0190] Formation of a fiber: Currently, organic small molecular fibers may only be produced at a centimeter scale. This disclosure introduces a method where materials are melted at 170 °C and rapidly cooled to 80 °C to form a supercool liquid. By thermally drawing from the viscous supercooled liquid state, fibers may be efficiently produced.

[0191] Formation of a 3D Object: Traditional methods for creating organic small molecular 3D objects typically require support matrices, such as UV glue or silica molds. This disclosure simplifies the process by melting glass (G@TTPS and G@TTPO) at 170 °C and quickly cooling it to 80 °C. A 3D object, such as a stamp, may then be formed by pressing the supercool liquid.

[0192] Thermoplasiticiy: Once shaped, small molecular objects generally cannot be reshaped without re-melting. However, this disclosure demonstrates that G@TTPS exhibits thermoplasticity. By heating it from room temperature to 60 °C, the material reaches a soft, highly viscous state (105 Pa s), allowing it to be cut and adhered to a 3D object.

[0193] Previous research focused solely on the luminescence characteristics of TTPO in powder form. The results indicated that TTPO is not an ideal phosphorescent molecule. The present disclosure is focused on the physical properties of TTPO, especially its glass properties and potential as an excellent host material for generating afterglow through a host-guest doping strategy. Notably, we captured its viscous supercooled liquid state and utilized this property to fabricate meter-scale fibers and 3D objects. Furthermore, we optimized the structure of TTPO to form TTPS, which exhibits a larger difference between glass transition temperature and crystallization temperature. These modifications enable TTPS to exhibit thermoplasticity, making it suitable for reshaping the formed glass.

[0194] Commercial Applications:

[0195] 1) Large-area preparation of organic afterglow small molecules: As a proof of concept, a uniform, transparent glass disc with a 3 cm diameter was produced, demonstrating afterglow properties that could advance the design of optical devices.

[0196] 2) Flexible meter-scale fiber development: A flexible fiber of meter-scale length was fabricated, which may be utilized in designing optical fibers with afterglow characteristics.

[0197] 3) Thermoplasticity for reshaping : The thermoplastic nature of the small molecular glass enables reshaping, making it adaptable for complex and precise applications.

[0198] Experimental

[0199]

[0200] Scheme 1. Synthesis of TTPO Synthesis of TTPO. Tri(o-tol) phosphine (100 g, 328 mmol) was dissolved in 500 mL of dichloromethane (DCM) and placed in a 0°C ice bath with vigorous stirring. Hydrogen peroxide (27 mL, 394 mmol, 35% in water) was added dropwise to the solution over 5 minutes. The reaction mixture was stirred for an additional 30 minutes until the complete consumption of tri(o-tol) phosphine, as monitored by TLC. The reaction mixture was then carefully added dropwise to a saturated sodium sulfite solution at 0 °C to quench the excess H2O2. The resulting mixture was extracted with dichloromethane three times, and the combined organic layers were evaporated under reduced pressure to yield the crude product as a white powder. The product was purified by

[0201]

[0202] Scheme 2. Synthesis of TTPS

[0203] Synthesis of TTPS. Under an argon atmosphere, tri(o-tol) phosphine (100 g, 328 mmol) and sulfur (10.5 g, 328 mmol) were dissolved in 300 mL of toluene. The reaction mixture was stirred under reflux overnight until the complete consumption of tri(o-tol) phosphine, as confirmed by TLC. After allowing the mixture to cool naturally, it was extracted three times with dichloromethane. The combined organic layers were evaporated under reduced pressure to yield the crude product as a yellow powder. The product was then purified by chromatography on a silica-gel column using ethyl acetatehexane (8: 1, v: v) as the eluent, followed by recrystallization, resulting in the final product as a white powder (96.4 g, 87% yield)XH NMR (400 MHz, CDCh) 6 7.53-7.61 (m, 3H), 7.37 - 7.43 (m, 3H), 7.18 - 7.27 (m, 6H), 2.36 (s, 9H).13C NMR (101 MHz, CDCh) 6 142.5 (d), 133.2 (d), 132.4 (d), 129.8, 128.7, 125.5 (d), 22.0.

[0204] Synthesis of l-(2-bromophenyl)-lH-benzo[f]indole (BrPhBd)

[0205] lH-benzo[f]indole (50.0 mg, 299.0 57 mmol), sodium hydride (14.4 mg, 358.8 mmol) dispersed in 60% mineral oil, were dissolved in 10 mL of DMF at 0 °C. l-Bromo-2- fluorobenzene (62.8 mg, 358.8 mmol) was added after 30 mins stirring. Then the reaction mixture was heated to reflux and stirred for 12 hours. After cooling to room temperature, the reaction mixture was slowly poured into 300 mL of ice water with stirring. The crude product was purified by chromatography on a silica gel column with dichloromethane-hexane (1 / 5, v / v) as eluent to afford the target product of BrPhBd as white powder (47.4 mg, 49.2% yield).XH NMR (400 MHz, CDCI3) 6 8.17 (s, 1H), 7.96 (d, 2H), 7.86 (d, 1H), 7.72 - 7.66 (m, 2H), 7.52 - 7.47 (m, 3H), 7.40 - 7.34 (m, 2H), 6.82 (s, 1H).13C NMR (101 MHz, CDCh) 6 138.81, 137.48, 134.29, 132.73, 130.55, 130.04, 130.00, 129.66, 129.13, 128.64, 128.30, 127.60, 124.11, 123.04, 122.28, 118.62, 106.11, 102.77.

[0206] General methods

[0207] The UV lamp used for photoactivation was purchased from sanjicha (Aex = 365 nm, 5 W, dmirror = 1.5 cm). Proton and carbon nuclear magnetic resonance (!H NMR and 13C NMR) spectra for the compounds were attained from a Bruker ARX 400 NMR spectrometer with Chloroform-d (CDCh) as solvent. Cyclic voltammetry data were attained from an AUTOLAB PGSTAT302N instrument. The measurements were conducted in desiccated and oxygen-free acetonitrile, employing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPFe) as the supporting electrolyte. A platinum wire served as the counter electrode, while a glassy carbon electrode was employed as the working electrode, and an Ag / Ag+electrode functioned as the reference electrode. Redox potentials were calibrated relative to ferrocene / ferrocenium (Fc / Fc+). UV-vis absorption spectrum of each material was obtained on a UV-vis spectrometer (Shimadzu UV-2600) with their DCM solutions (50 pM). Photoluminescence (PL) spectra and delayed emission spectra were measured on an Ocean Optic QE 65 Pro spectrometer with a reflection probe R600-125F. Phosphorescence lifetimes were recorded with an Edinburgh Instruments Spectrofluorometer (FLS 1000). The phosphorescent quantum yields of the doping systems were measured by FLS 1000 Spectrofluorometer with an integrating sphere. Confocal microscope image was recorded using a confocal laser scanning microscopy (CLSM) (Leica TSC SP8, Germany).

[0208] Fabrication methods

[0209] Taking Cor@TTPS as an example:

[0210] Fiber: 2 grams of TTPS powder and 20 mg of coronene was melted at 170 °C in a dish. The molten liquid was quickly transferred onto an 80 °C hot plate, from which a meterscale fiber could be drawn from the supercooled liquid. Stamp: 2 grams of TTPS powder and 20 mg of coronene was melted at 170 °C in a spoon. When the supercooled liquid reached 80 °C, an NUS mold stamp was pressed onto it. After removing the mold, an NUS afterglow glass was obtained.

[0211] Cut and Stick: The prepared G@TTPS was heated to 60 °C, and a knife and ruler were used to cut the irregular glass into the desired shape. The cut pieces may be joined by ensuring a tight surface contact, and their high viscosity helps them adhere together effectively.

[0212] Results and Analysis

[0213] Firstly, TTPO and TTPS were synthesized as shown in Scheme 1 and Scheme 2. The inventors then investigated the glass properties of both TTPO and TTPS (Fig. 1). As depicted in Fig. la, the glass transition temperatures of TTPO and TTPS are 25 °C and 32 °C, respectively, with melting temperatures of 156 °C and 165 °C. Both TTPO and TTPS exhibit a viscous supercooled liquid state during the cooling process. For example, when a shear deformation at a rate of 30 s-1was applied to TTPO at 170 °C in its molten state and at 85 °C in its supercooled liquid state, the molten liquid had a viscosity of 0.03 Pa s. The fragile supercooled liquid, however, underwent shear-induced crystallization, triggered by heterogeneous nucleation at the interface between the upper plate and the sample during viscosity measurement. During the initial 6 seconds, the viscosity of the supercooled liquid was increased from 379 Pa s to 1057 Pa s, staying within a workable range for processing. After 7 seconds, rapid crystallization occurred, as indicated by a sharp rise in viscosity from 1989 Pa s to 109Pa s (Fig. lb). Although the supercooled liquid tends to crystallize when disturbed, its viscous nature allows it to be processed similarly to inorganic glass. TTPS has a higher glass transition temperature, and the 70 °C difference between its glass transition temperature and crystallization point provides more operational opportunities compared to TTPO, which has a smaller temperature difference of 25 °C. Therefore, TTPS glass exhibits thermoplastic properties (Fig. lc). When heated to 60 °C, TTPS softens, reaching a viscosity of around 105Pa s, making it suitable for reshaping.

[0214] To examine the afterglow properties, we firstly analyzed the crystals. TTPO was tightly packed via various and large amount of CH -0 (2.6-2.9 A), C-H •■•n (2.9 A) and C-H - H (2.4 A) intermolecular interactions (Fig. 3a). Those intermolecular interactions help restrict molecular motion and provide a rigid environment even in the amorphous state.

[0215] 7HBCz, BrPhBd 1,8-NA were selected as dopants. The low-viscosity TTPO molten liquid can be regarded as an organic solvent with excellent solubility and its moderate melting point ensures that the dopants don't decompose during dissolving. By blending those dopants into the TTPO molten liquid, 7HBCz, 1,8-NA and BrPhBd could be homogeneously dissolved in the TTPO melting liquid at a 1% weight ratio, respectively. Following the rapid cooling method, the inventors managed to create uniform and transparent rigid glassy solid systems without experiencing phase separation. The rigid glassy solid systems exhibit over 87% transmission in the visible light range while absorbing light in the UV range, depending on the absorption characteristics of each dopant and the TTPO host itself (Fig. 2b).

[0216] A photoactivation behavior was observed when the system was irradiated by a 365 nm flashlight. After 10 seconds of irradiation (5W 365 nm torchlight), clear and bright afterglow could be observed from each doping system. The highly efficient afterglow was given in their amorphous forms, as confirmed by p-XRD experiments where no diffraction signal could be detected (Fig. 2c). The blended 7HBCz@TTPO system exhibits a green afterglow lasting 15 seconds, clearly visible to the naked eye. The system's main emission peaks occur at 487, 526, and 570 nm, with a lifetime of 1.6 seconds. The decay profile follows an exponential law, and the emission matches the phosphorescence observed for the film of 7HBCz in the polystyrene (PS) system, suggesting that the phosphorescence is originated from 7HBCz. 1,8-NA @ TTPO system exhibits a 450 ms yellow afterglow at 540 nm. The afterglow decay profile follows an exponential law decay, and the phosphorescence peak is at 540 nm, 660 nm, which is consistent with the phosphorescence of 1,8-NA @ PS at 77K. An orange afterglow was observed in the BrPhBd@TTPO system with a 322 ms lifetime.

[0217] Similarly, Py, BeP, and Cor were each blended into TTPS at a 1% weight ratio. The Py@TTPS system displays a red afterglow emission with a lifetime of 332 ms. The Bep@TTPS system exhibits an orange afterglow with a lifetime of 796 ms. The Cor@TTPS system shows a green RTP with a lifetime of 1.75 seconds (Fig. 3).

[0218] Phosphine oxides and sulfides are usually regarded as chemical waste generated in thousands of tons per year from various valuable organic reactions in the chemical industry. However, the regeneration of them into useful phosphine typically involves the use of toxic reagents and harsh conditions, posing potential economic and environmental burdens. Consequently, there is a pressing need to convert wastes into valuable resources. Upon vitrifying the TTPO or TTPS melting liquid to room temperature, the supercooled liquid gradually becomes more and more viscous until it solidifies completely. The presence of a viscous supercooled liquid allows us to follow a processing method similar to that used for inorganic glass. Large area preparation of small organic molecules is desirable to display application. Through the vitrification technique, the inventors were able to create a uniform and transparent afterglow glass with a 3 cm diameter (Fig. 4a). This high transparency and large area preparation ability makes the afterglow glass promising for optical device development. The viscous state also enables us to shape materials into desired forms. Hot-pressing on the viscous supercooled liquid, we successfully created an NUS stamp with a 3D structure (Fig. 4b).

[0219] With the rapid development of electronics and artificial intelligence in recent decades, fibers have played an important role in wearable devices, particularly as intelligent textile sensors. However, forming meter scale and flexible fibers is challenging in pure small organic molecular systems. The high demands and experience-dependent nature of crystal growth technology, and the lack of broadly applicable design principles for controlling shape and size, limit the development of organic small molecule fibers. Those drawbacks limit their applications in the field of advanced textile for intelligent wearable devices, energy conversion and storage, optical devices such as fiber laser and optical waveguide. Currently only a very small number of fibers based on organic small molecules can reach centimeter-level, with most still at the micron or even nano level. Developing a robust and universally applicable method for producing long small molecule fibers with practical application value is crucial for exploring new types of devices.

[0220] Inspired by traditional inorganic glass fiber processing techniques, the inventors managed to produce a meter-scale fiber (0.5 m long with 100 ± 10 pm in diameter (Fig.

[0221] 4c), 1 m long (Fig. 5)) simply through thermal drawing from the viscous supercooled liquid. As far as the inventors know, this is the longest fiber made purely from small organic molecules so far. Due to the isotropic and uniform nature of glass, weak and dispersive interactions are distributed evenly in three orthogonal directions, therefore fibers demonstrate remarkable flexibility and mechanical strength. The coiled fiber can be stretched into a straight configuration, and a 0.5 mg fiber can support weights of up to 500 mg while retaining its afterglow properties. These characteristics make it promising for potential applications in advanced textiles and displays. The TTPS glass exhibits thermoplastic properties, allowing it to be reshaped when heated from room temperature. It reaches a softening point at 60 °C, enabling the irregular and soft glass to be easily cut into two triangular pieces. Due to its high viscosity (105 Pa s), these pieces can be bonded together to form a simple 3D object (Fig. 6). This easy reshaping capability opens new possibilities for incorporating this material into complex and precise devices. Results and discussion

[0222] To demonstrate the molecular glass design strategy, TTPO was firstly prepared from tris (2-methylphenyl) phosphine (TTP) on a hundred-gram scale by using H2O2 as an oxidizer. The low-cost reactants, mild reaction conditions (1 h, 99% yield), and simple purification via recrystallization make this reaction atom-economic to yield cost-effective TTPO (Fig. 8a). The methyl group introduced at the ortho position of three phenyl rings resulted in the symmetry disruption of the phenyl group which led to conformational diversity. Four distinct energy conformations have been predicted, with exo3 being the most stable conformation, as indicated by the single crystal structure. The least stable exoo conformation exhibits a 33.5 kJ-mol-1higher relative energy compared to that of exo3 (Fig. 8b). To arrange disordered molecules into an ordered and stable conformation, interconversion barriers must be overcome, which slows down the crystallization rate and results in a glass transition temperature at 299 K (Fig. 11). On the other hand, the tetrahedral structure led to weak conjugation between the phosphine oxide and phenyl groups. As a result, methylation does not alter its triplet energy levels compared to TPPO (Fig. 13), which ensures that TTPO is suitable as a good phosphorescent host in terms of energy levels.

[0223] Glass forming is a kinetic process where solids form before molecules are arranged into order. Therefore, vitrification is the key step in creating a disordered microstructure. By rapidly cooling samples from the melted state (433 K) to room temperature, a uniform and transparent film was easily produced. In contrast, allowing the sample to cool naturally resulted in the formation of a crystalline structure (Fig. 14). To assess the glass quality, Kissinger analysis was used to estimate the overall apparent activation energy of crystallization from amorphous glass (equation (1)).

[0224]

[0225] In Equation 1, / ? is the heating rate in K min’1, Tpis the peak crystallization temperature where the crystallization rate reaches the maximum, A is the frequency factor in s1, R is the universal constant (8.314 J mol ^K1), and Ea is the overall apparent activation energy from glass to crystal in J mol-1. By plotting the natural logarithm of heating rates against the maximum rate of crystallization temperature (Tp-1), a linear relationship may be observed, where the overall activation energy was calculated as 47 ± 2 kJ mol’1, resulting in moderate morphology stability (Fig. 8c, Fig. 15). The Kissinger analysis diagram demonstrates the effectiveness of o-methylation in enhancing TTPO's glassforming ability. A key characteristic of MG is the presence of a temperature-dependent viscous supercooled liquid state. Rheological measurements were conducted using a rotational rheometer, clearly demonstrating that the melting liquid and supercooled liquid exhibit temperature-dependent viscosity behavior (Fig. 8d). A shear deformation at a rate of 30 s1was applied to the melting liquid viscosity at 443 K and the supercooled liquid at 358 K. The melting liquid viscosity is 0.03 Pa-s, while the fragile supercooled liquid undergoes shear-induced crystallization, a process triggered by heterogeneous nucleation at the interface between the upper plate and the sample during viscosity measurement. From the initial stage to 6 seconds, the viscosity of supercool liquid increased from 379 Pa-s to 1057 Pa-s. It is important to note that the viscosity remains within the working range and is suitable for processing. After 7 seconds, rapid crystallization was observed, indicated by a significant increase in viscosity from 1989 Pa-s to 109 Pa-s. Although the supercooled liquid tends to crystallize under disturbances, its viscous nature allows us to process it similarly to inorganic glass.

[0226] From the crystal analysis, TTPO is tightly packed due to a variety of intermolecular interactions, including numerous C-H---0 (2.6-2.9 A), C-H---n (2.9 A) and C-H---H (2.4 A) interactions (Fig. 9a). Additionally, the presence of methyl groups introduces motion barriers, further restricting molecular movement and contributing to a rigid environment within the crystal. Considering its high triplet energy level, TTPO has the potential to be a room-temperature phosphorescence (RTP) host. As proof of the concept, twist molecule tris(l-naphthyl) phosphine (TNpP) was doped into TTPO at a 1 wt% concentration by slowly evaporating the solvent. The resulting crystalline solid exhibited a bright yellow-green afterglow with a lifetime of 270 ms after 3 seconds of photoactivation (365 nm, 5 W, UV lamp) as shown in the Fig. 9d. In contrast, no RTP was observed when the same excitation was applied to pure TNpP and TTPO powders. The RTP emission from the doping system is in line with the phosphorescence of TNpP@Toluene at 77 K, instead of TTPO powder, therefore, we confirmed that the RTP emission originated from TNpP rather than TTPO (Fig. 19). To test whether glassy TTPO could maintain the same stabilization effect as powder form, glassy samples with the same doping concentration were prepared. Following the rapid cooling method, the inventors managed to create uniform and transparent rigid glassy solid systems without experiencing phase separation. The rigid glassy solid systems exhibit up to 87% transmission in the visible light range while absorbing light in the UV range, depending on the absorption characteristics of each dopant and the TTPO host itself (Fig. 9b). A photoactivation behavior was observed when the system was irradiated by a 365 nm UV lamp. After 10 seconds of irradiation, clear and bright afterglow could be observed from the TNpP@TTPO system even as amorphous forms, as confirmed by p-XRD experiments (Fig. 9c). Remarkably, the resulting transparent and uniform TTPO doping glass exhibited nearly identical photophysical properties (Fig. 9e and Fig. 16). This consistency indicates that the rigid environment is effectively maintained in the amorphous state and capable of blocking triplet quenching factors such as oxygen and moisture.

[0227] To demonstrate the excellent dopant tolerance of TTPO, a variety of molecules were selected as dopants and blended with TTPO at 1 wt%. These included simple and small size molecule methyl 2-amino-3-methoxybenzoate (MAMOBZ), organic ion dye 2,6-dibromo-4,4-difluoro-l,3,5,7-tetramethyl-8-phenyl-4-bora-3a,4a-diaza-s-indacene (DiBrBDP), molecules with planar structures, such as coumarin 1 (CM1), 7H156 benzo[c]carbazole (7HBCz), 5H-benzo[b]carbazole (5HBCz), 1,8-naphthalic anhydride (1,8-NA) and pyrene (Py), as well as twisted structures like (diphenyl)(l-naphthyl)amine (NpDPA) (Fig. 17). After employing the melting-rapid cooling method, both doping systems may form a uniform and transparent glassy state without phase separation, as confirmed by p-XRD (Fig. 9c). Following 10 seconds of photoactivation, all doping systems exhibited highly efficient afterglow, ranging from cyan to near infrared with lifetimes varying from 3 ms to 1695 ms (Fig. 9e-g, 10a, Fig. 24). These delayed emissions differed from the fluorescence of the guest molecules but were consistent with their phosphorescence at 77 K (Fig. 19). This indicates that the doping system exhibited RTP arising from the triplet-state emission of the guests themselves. Notably, DiBrBDP demonstrated a near infrared afterglow with a maximum emission at 767 nm with a 3 ms lifetime. In the Py@TTPO system, red emission was observed with a maximum of 592 nm and a lifetime of 247 ms. An invisible strong delayed fluorescence at 397 nm was detected in the Py@TTPO system, which was confirmed to originate from the triplet-triplet annihilation (TTA) process of pyrene (Fig. 25). However, most aromatic compounds have low triplet energy levels due to the extensive delocalization of n-electrons across their conjugated systems, and significant overlap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). This overlap results in large singlet-triplet energy gaps (A EST), as the A EST is proportional to twice the electron exchange energy which is determined by the degree of HOMO-LUMO orbital overlap. To date, strategies for achieving deep blue RTP are still rare. Herein a simple violet afterglow is realized by embedding 1-pyrene carboxylic acid (PCA), a dopant with greater conjugation than pyrene, into the amorphous TTPO matrix. This design leverages the up-conversion emission characteristics of the TTA process, producing a violet afterglow with a strong delayed fluorescence at 410 nm and a weak phosphorescence at 623 nm. The photophysical properties of guest@TTPO are summarized in Table 1, indicating that afterglow systems exhibit a low non-radiative decay rate (fcir) from 0.58 to 3.95 s’1, supporting its role as an excellent afterglow host for diverse structural dopants.

[0228] To further investigate the luminescence mechanism, the inventors doped the guest molecules into PMMA, a commonly used rigid matrix for enhancing RTP and studied their afterglow behaviors. All guest@PMMA systems exhibit significantly weaker afterglow compared to the guest@TTPO systems under the same excitation conditions (Fig. 10b, Fig. 26). A rigid environment typically restricts molecular vibration and reduces thermal disturbances in excited-state molecules, which may induce fine structure of the spectrum. By comparing the afterglow spectra of guest molecules in both systems, clearer fine spectral structures were observed in guest@TTPO, matching the phosphorescence spectra in toluene at 77 K. This confirms that TTPO provides a highly rigid environment, effectively suppressing non-radiative decay processes.

[0229] Beyond its rigid nature, TTPO also acts as an energy transfer platform to enhance afterglow with its lowest triplet energy level (Ti = 2.95 eV) positioned between the singlet (Si 2.88 to 3.56 eV) and triplet states (Ti 2.08 to 2.86 eV) of the guest molecules (Fig. 27). Further theoretical calculations based on the guest molecules and their corresponding guest@TTPO pairs were carried out, and the results are shown in Fig. 10c and Fig. 28 to 43. As exemplified by BrPhBd@TTPO, the host-guest pairing significantly benefits from additional intersystem crossing (ISC) channels with enhanced spin-orbit coupling (SOC) values. These new ISC pathways are not present in the single BrPhBd molecule but arise from host-guest pairing. As a result, multiple ISC channels, such as Si ^Ts (A Esr= 0.13 eV; SOC = 0.02 cm1), Si ^T6(A EST = 0.15 eV; SOC = 0.06 cm'x), Si -► T? ( . EST = 0.16 eV; SOC = 0.22 cm1) are activated in the region of (A EST < 0.3 eV (Fig. 10c). Analysis from the newly generated triplet levels, electron-hole densities of Te and T? were localized on the TTPO component, although this process was less efficient compared to the transition from the guest's Si to Tnstate (Fig. 39). Therefore, a triplet-triplet energy transfer process might also be involved in the luminescence mechanism as a less dominant pathway to boost the formation of triplet excitons and improve the RTP performance for these guest@TTPO systems (Fig. lOd). This enhancement highlights the pivotal role TTPO plays not only in providing a rigid environment but also in actively supporting the ISC and energy transfer processes that lead to superior afterglow properties. However, no additional ISC channels were activated in the DiBrBDP-TTPO pair from the calculation results due to the mismatched energy between TTPO and DiBrBDP (Fig. 44). Therefore, the rigid microenvironmental plays the dominant role in stabilizing triplet excitons and facilitating RTP emission from DiBrBDP.

[0230] Phosphine oxides are usually regarded as chemical waste generated in thousands of tons per year from various valuable organic reactions in the chemical industry. However, the regeneration of phosphine oxides into useful phosphine typically involves the use of toxic reagents and harsh conditions, posing potential economic and environmental burdens. Consequently, there is a pressing need to convert waste into valuable resources. Upon vitrifying the TTPO melting liquid to room temperature, the supercooled liquid gradually becomes more and more viscous until it solidifies completely. The presence of a viscous supercooled liquid allows the inventors to follow a processing method like that used for inorganic glass. For example, large-area preparation is desirable for display applications, as it ensures consistent performance across larger surfaces - an essential factor for commercial viability and the widespread adoption of consumer products. Through the vitrification technique, the inventors were able to create a uniform and transparent afterglow glass with a 3.0 cm diameter (Fig. 4a). This high transparency and large area preparation ability make the afterglow glass promising for optical device development. The viscous state also enables the inventors to shape materials into desired forms. By hot-pressing the viscous supercool liquid, we successfully created an NUS stamp with a 3D structure (Fig. 4b, Fig. 45). Beyond hot-pressing, the long-lasting viscous supercooled liquid offers the potential for thermal fiber drawing. The inventors managed to produce a meter-scale fiber (0.5 m long with 100 ± 10 pm in diameter (Fig. 4c), 1 m long (Fig. 5)) simply through thermal drawing from the viscous supercool liquid. To the best of the inventors' knowledge, this is the longest afterglow fiber made purely from small organic molecules, as only a limited number of fibers based on organic small molecules can reach centimeter-level, with most still at the micron or even nano level. Due to the isotropic and uniform nature of glass, weak and dispersive interactions are distributed evenly in three orthogonal directions, therefore fibers demonstrate remarkable flexibility and mechanical strength. The coiled fiber may be stretched into a straight configuration, and a 0.5 mg fiber may support weights of up to 500 mg without breaking. The successful fabrication of long and flexible fibers could significantly enhance the development of innovative wearable devices, especially in applications such as intelligent textile sensors and optical devices, including fiber lasers and optical waveguide.

[0231] Conclusion In conclusion, the inventors have developed an effective strategy for designing an afterglow molecular glass host. The designed TTPO MG may be readily produced on a hundred-gram scale. The introduction of rigid methyl groups disrupts the symmetry of the phenyl group, leading to diverse conformations, excellent glass forming ability, and enabling a temperature-dependent, processable viscous supercooled liquid state. The efficient afterglow is achieved using a host-guest strategy, producing full-color emission ranging from violet to near-infrared with an ultralong lifetime. TTPO afterglow systems can be fabricated into a uniform, transparent film within one minute, from melting to cooling. The low-viscosity melt and small molecular size of TTPO facilitate the dissolution of most organic molecules. Additionally, the amorphous nature of TTPO at room temperature prevents phase separation in systems with significant host-guest structural differences. Based on the investigation of the luminescence mechanism, TTPO not only offers a highly rigid microenvironment but also functions as an energy transfer bridge, facilitating the generation of afterglow. As a result, TTPO demonstrates strong potential as a versatile afterglow host. These advantages endow TTPO with great potential to act as an excellent platform for the rapid screening of phosphorescent molecules. Additionally, the existence of a supercooled liquid state allows the glass system to be processed similarly to inorganic glass. Objects with 3D structures and meter-long fibers are fabricated without losing their afterglow properties. With its advantages in cost-effective large-scale synthesis, tolerance to various dopants, and high processability, TTPO-based afterglow systems hold great potential for new applications and the design of innovative devices.

[0232] Methods

[0233] General methods

[0234] Proton, carbon and phosphorus nuclear magnetic resonance CH NMR,13C NMR,31P NMR) spectra for the TTPO were attained from a Bruker ARX 400 NMR spectrometer with Chloroform-d (CDCh). The Kissinger analysis for TTPO activation energy from glassy to crystalline state was determined by using a differential scanning calorimeter (PerkinElmer 8000 DSC). Thermogravi metric analysis of TTPO was performed by using a thermogravimetric analyzer (Shimadzu DTG-60 AH). The viscosity of TTPO supercool liquid was measured by using a rheometer (Anton Paar MCR-9). UV-279 vis absorption spectrum of each compound was obtained using a UV-vis spectrometer (Shimadzu UV-2600). Delayed emission spectra were collected with the Ocean Optic QE 65 Pro spectrometer. Photoluminescence (PL) spectra and phosphorescence lifetimes were recorded with an Edinburgh Instruments Spectrofluorometer (FLS 1000). The quantum yields of the doped systems were measured by FLS 1000 Spectrofluorometer with an integrating sphere. The crystal structure of TTPO is available from the CCDC database (CCDC number:285 2076603).

[0235] Theoretical Calculations

[0236] Density functional theory (DFT) computations, encompassing geometrical optimization and electronic properties evaluations at ground states, were conducted using the Gaussian 09 software package at the B3LYP / 6-311g(d) level. The energy levels of the excited states were computed using the time-dependent DFT (TDDFT) method at the same B3LYP / 6-311g(d) level. The spin-orbit coupling (SOC) matrix elements between singlet and triplet excited states were calculated by ORCA 5.0.4 using the B3LYP / G method with DKH2 DKH-def2-TZVP basis sets. Analysis was performed using Multiwfn 3.8.

[0237] Hot-pressing and fiber fabrication methods

[0238] Stamp: TTPO (2.0 g) and guest (20 mg) were melted at 170 °C in a spoon. When the supercooled liquid reached 80 °C, an NUS mold stamp was pressed onto it. After removing the mold, an NUS afterglow glass stamp was obtained.

[0239] Fiber: TTPO (1.0 g) and guest (10 mg) were melted at 170 °C in a dish. The molten liquid was quickly transferred onto an 80 °C hot plate, from which a meter-scale fiber could be drawn from the supercooled liquid.

[0240] PMMA samples preparation

[0241] 100 mg of PMMA and 1 mg of the guest compound were dissolved in 1 mL of dichloromethane. To prevent oxygen quenching, the mixed solution was drop-cast onto a quartz substrate and allowed to dry naturally in a glove box. After drying, the sample was encapsulated with another piece of quartz using a UV-curing resin, resulting in the preparation of the guest@PMMA film.

[0242] Materials and syntheses

[0243] Synthetic routes for tri(2-methylphenyl) phosphine oxide. I-Methyl 2-amino-3-methoxybenzoate, coumarin 1, 7H-benzo[c]carbazole, tris (1-naphthyl) phosphine, (diphenyl)(l-naphthyl) amine, 1,8-naphthalic anhydride, 5 / 7-benzo[£>]carbazole, pyrene and 2,6-dibromo-4,4-difluoro-l,3 ,5, 7-tetramethyl-8-phenyl-4-bora-3a,4a- diaza-s-indacene, pyrene carboxylic acid were purchased from TCI and sigma. All the products were purified by column chromatography before use.

[0244] Synthesis of tri(2-methylphenyl) phosphine oxide (TTPO)

[0245]

[0246] Scheme 1. Synthesis of TTPO

[0247] Tri(2-methylphenyl) phosphine (100.0 g, 328 mmol) was dissolved in 500 mL of dichloromethane (DCM), and the flask was placed in an ice bath at 0 °C under vigorous stirring. Hydrogen peroxide (H2O2, 27 mL, 394 mmol, 35% in water) was added dropwise over 5 minutes, followed by continued stirring for an additional 30 minutes until complete consumption of tri(2-methylphenyl) phosphine was confirmed by TLC. The reaction mixture was carefully quenched by dropwise addition into a saturated sodium sulfite solution at 0 °C to neutralize excess H2O2. The resulting mixture was extracted with dichloromethane three times. The combined organic layers were concentrated under reduced pressure to afford the crude product as a white powder. The product was purified by silica-gel column chromatography followed by recrystallization, yielding TTPO as a white solid with 99% yield (104.5 g). TTPOXH NMR (400 MHz, CDCh) 5 7.41-7.44 (m, 3H), 7.29-7.32 (3, m), 7.06-7.17 (m, 6H), 2.49 (s, 9H).13C NMR (100 MHz, CDCh) 6 143.52 (d, J= 8 Hz), 132.92 (d, J= 13 Hz), 132.05 (d, J= 10 Hz), 131.87 (d, J= 3 Hz), 130.5 (d, J= 101 Hz), 125.51 (d, J= 12 Ha2).31P NMR (162 MHz, CDCh) 37.3.

[0248] Table 1: Photophysical properties of different doping systems

[0249] &

[0250]

[0251] <

[0252]

[0253] where &PL is the total photoluminescence quantum yield. Qphos is the phosphorescence quantum yield, rp is the lifetime of phosphorescence. QIC is the quantum efficiencies of internal conversion. QISC is the quantum efficiencies of intersystem crossing, kp is the rate constant of phosphorescence, knr is the rate constant of non-radiative decay.

[0254] It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

[0255] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0256] Throughout this specification and the claims which follow, unless the context requires otherwise, the phrase "consisting essentially of", and variations such as "consists essentially of" will be understood to indicate that the recited element(s) is / are essential i.e. necessary elements of the invention. The phrase allows for the presence of other non-recited elements which do not materially affect the characteristics of the invention but excludes additional unspecified elements which would affect the basic and novel characteristics of the method defined.

[0257] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

Claims1. An afterglow material, comprising:a) an amorphous matrix comprising a compound of Formula (I):whereinX is selected from 0 and S; andRi, Rz and R3 are independently selected from optionally substituted alkyl, optionally substituted aryl, and optionally substituted heteroaryl; andb) a dopant homogenously dispersed within the amorphous matrix;wherein the dopant is at a % weight ratio of about 0.1% to about 10 % relative to the amorphous matrix.

2. The afterglow material according to claim 1, wherein Ri, Rz, and 3 are independently C1-C5 alkyl.

3. The afterglow material according to claim 1 or 2, wherein the compound of Formula (I) is selected from:

4. The afterglow material according to any one of claims 1 to 3, wherein the compound of Formula (I) is characterised by a melting temperature of about 140 °C to about 170 °C.

5. The afterglow material according to any one of claims 1 to 4, wherein the compound of Formula (I) is characterised by a crystallisation temperature of about 40 °C to about 110 °C.

6. The afterglow material according to any one of claims 1 to 5, wherein thecompound of Formula (I) is characterised by a glass transition temperature of about 20 °C to about 40 °C.

7. The afterglow material according to any one of claims 1 to 6, wherein the dopant exhibits luminescence upon excitation with electromagnetic radiation.

8. The afterglow material according to any one of claims 1 to 7, wherein the dopant comprises optionally substituted conjugated aryl or optionally substituted conjugated heteroaryl.

9. The afterglow material according to any one of claims 1 to 8, wherein the dopant is selected from coronene, tris(l-naphthyl) phosphine (TNpP), methyl 2-amino-3-methoxybenzoate (MAMOBZ), 2,6-dibromo-4,4-difluoro-l,3,5,7-tetramethyl-8-phenyl-4-bora-3a,4a-diaza-s-indacene (DiBrBDP), coumarin 1 (CM1), 7H-benzo[c]carbazole (7HBCz), 5H-benzo[£>]carbazole (5HBCz), 1,8-naphthalic anhydride (1,8-NA) and pyrene (Py), (diphenyl)(l-naphthyl)amine (NpDPA), 1-pyrene carboxylic acid (PCA or PyCOOH), l-(2-bromophenyl)-lHbenzo[f]indole (BrPhBd), Benzo[e]pyrene (BeP) and a combination thereof.

10. The afterglow material according to any one of claims 1 to 9, wherein the afterglow material is characterised by a weight ratio of compound of Formula (I) to dopant of about 1000:1 to about 10:1.

11. The afterglow material according to any one of claims 1 to 10, wherein the afterglow material is characterised by a degree of crystallinity of less than 5%.

12. The afterglow material according to any one of claims 1 to 11, wherein the afterglow material is characterised by a luminescence wavelength of about 350 nm to about 1500 nm.

13. The afterglow material according to any one of claims 1 to 12, wherein the afterglow material is characterised by a luminescence lifetime of at least about 1 ms.

14. The afterglow material according to any one of claims 1 to 13, wherein the afterglow material is characterised by a luminescence decay lifetime of at least about 1 ms.

15. The afterglow material according to any one of claims 1 to 14, wherein the afterglow material is characterised by a photoluminescence quantum yield of about 5% to about 45% when excited by at about 365 nm.

16. The afterglow material according to any one of claims 1 to 15, wherein the afterglow material is characterised by a non-radioactive decay rate of about 0.2 s'1to about 5 s'1.

17. The afterglow material according to any one of claims 1 to 16, wherein the afterglow material is characterised by a viscosity of about 0.1 x 105Pa-s to about 10 x 105Pa-s when heated to about 55 °C to about 65 °C.

18. The afterglow material according to any one of claims 1 to 17, wherein the afterglow material is formed in a mould or as a fibre with a diameter of about 50 pm to about 200 pm.

19. A method of fabricating an afterglow material according to any one of claims 1 to 18, comprising:a) melting a compound of Formula (I) to form a molten liquid;b) homogenously dispersing a dopant in the molten liquid;c) supercooling the molten liquid of step b) to a temperature above its glass transition temperature and from about 20°C to about 100 °C to form a supercooled liquid; andd) solidifying the supercooled liquid by further cooling the supercooled liquid to form the afterglow material.

20. The method according to claim 19, wherein step a) is performed at a temperature of about 150 °C to about 180 °C.

21. The method according to claim 19 or 20, wherein the molten liquid is characterised by a viscosity of about 0.01 Pa s to about 0.5 Pa s.

22. The method according to any one of claims 19 to 21, wherein step c) is performed at a cooling rate of about 10 °C / min to about 50 °C / min.

23. The method according to any one of claims 19 to 22, wherein step c) comprises supercooling the molten liquid to a temperature of about 70 °C to about 90 °C to form the supercooled liquid.

24. The method according to any one of claims 19 to 23, wherein the supercooled liquid is characterised by a viscosity of about 1 x 102Pa s to about 1 x 1011Pa-s.

25. The method according to any one of claims 19 to 24, wherein step d) is performed at a cooling rate of about 10 °C / min to about 50 °C / min to an ambient temperature.

26. The method according to any one of claims 19 to 25, wherein step d) comprises solidifying the supercooled material by hot-pressing the supercooled liquid into a mould or thermally drawing the supercooled liquid into a fibre.

27. An afterglow material according to any one of claims 1 to 18, wherein the amorphous matrix is formed by supercooling a molten liquid to a temperature above its glass transition temperature and from about 20°C to about 100 °C, the molten liquid comprising the compound of Formula (I) and the dopant.

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