Photoluminescence Quantum Yield Research Articles

Overcoming Thermal Quenching in X‐ray Scintillators through Multi‐Excited State Switching

AbstractX‐ray scintillators have gained significant attention in medical diagnostics and industrial applications. Despite their widespread utility, scintillator development faces a significant hurdle when exposed to elevated temperatures, as it usually results in reduced scintillation efficiency and diminished luminescence output. Here we report a molecular design strategy based on a hybrid perovskite (TpyBiCl5) that overcomes thermal quenching through multi‐excited state switching. The structure of perovskite provides a platform to modulate the luminescence centers. The rigid framework constructed by this perovskite structure stabilized its triplet states, resulting in TpyBiCl5 exhibiting an approximately 12 times higher (45 % vs. 3.8 %) photoluminescence quantum yield of room temperature phosphorescence than that of its organic ligand (Tpy). Most importantly, the interactions between the components of this perovskite enable the mixing of different excited states, which has been revealed by experimental and theoretical investigations. The TpyBiCl5 scintillator exhibits a detection limit of 38.92 nGy s−1 at 213 K and a detection limit of 196.31 nGy s−1 at 353 K through scintillation mode switching between thermally activated delayed fluorescence and phosphorescence. This work opens up the possibility of solving the thermal quenching in X‐ray scintillators by tuning different excited states.

Overcoming Thermal Quenching in X-ray Scintillators through Multi-Excited State Switching.

X-ray scintillators have gained significant attention in medical diagnostics and industrial applications. Despite their widespread utility, scintillator development faces a significant hurdle when exposed to elevated temperatures, as it usually results in reduced scintillation efficiency and diminished luminescence output. Here we report a molecular design strategy based on a hybrid perovskite (TpyBiCl5) that overcomes thermal quenching through multi-excited state switching. The structure of perovskite provides a platform to modulate the luminescence centers. The rigid framework constructed by this perovskite structure stabilized its triplet states, resulting in TpyBiCl5 exhibiting an approximately 12 times higher (45 % vs. 3.8 %) photoluminescence quantum yield of room temperature phosphorescence than that of its organic ligand (Tpy). Most importantly, the interactions between the components of this perovskite enable the mixing of different excited states, which has been revealed by experimental and theoretical investigations. The TpyBiCl5 scintillator exhibits a detection limit of 38.92 nGy s-1 at 213 K and a detection limit of 196.31 nGy s-1 at 353 K through scintillation mode switching between thermally activated delayed fluorescence and phosphorescence. This work opens up the possibility of solving the thermal quenching in X-ray scintillators by tuning different excited states.

Optical and scintillation properties of Er-doped La3Ga5SiO14 single crystals emitting near-infrared photons

0.5, 1, 2, and 5% Er-doped La3Ga5SiO14 (LGS) single crystals were synthesized by the Floating Zone method and the photoluminescence (PL) and scintillation properties were characterized. Emission peaks appeared at visible–near-infrared (NIR) regions. Their spectral features matched with those due to the 4f–4f transitions of Er3+. The PL quantum yields of 0.5, 1, 2, and 5% Er-doped samples were respectively 45.0, 73.3, 82.5, and 69.4%. The decay times due to the 2H9/2–4I15/2 transitions of Er3+ were obtained when visible ranges were monitored under excitation of both visible lights and X-rays. All the prepared samples showed good linearity between the X-ray exposure dose rate and scintillation signals in NIR ranges. The best lower detection limit in prepared samples was 5 mGy/h recorded by the 2% Er-doped LGS.

Through‐Space Charge‐Transfer Organogold(III) Complexes Enable High‐Performance X‐ray Scintillation and Imaging

AbstractOrganic scintillators have recently attracted growing attention for X‐ray detection in industrial and medical applications. However, these materials still face critical obstacles of low attenuation efficiency and/or inefficient triplet exciton utilization. Here we developed a new category of organogold(III) complexes, Tp‐Au‐1 and Tp‐Au‐2, through adopting a through‐space interaction motif to realize high X‐ray attenuation efficiency and efficient harvesting of triplet excitons for emission. Thanks to the efficient through‐space charge transfer process, this panel of complexes achieved higher photoluminescence quantum yield and shorter radiative lifetimes compared with the through‐bond reference complexes. Inspiringly, these organogold(III) complexes exhibited polarity‐dependent emission origins: thermally activated delayed fluorescence and/or phosphorescence. Under X‐ray irradiation, Tp‐Au‐2 manifested intense radioluminescence together with a record‐high scintillation light yield of 77,600 photons MeV−1 for organic scintillators. The resulting scintillator screens demonstrated high‐quality X‐ray imaging with >16.0 line pairs mm−1 spatial resolution, outstripping most organic and inorganic scintillators. This finding provides a feasible strategy for the design of superior organic X‐ray scintillators.

Through-Space Charge-Transfer Organogold(III) Complexes Enable High-Performance X-ray Scintillation and Imaging.

Organic scintillators have recently attracted growing attention for X-ray detection in industrial and medical applications. However, these materials still face critical obstacles of low attenuation efficiency and/or inefficient triplet exciton utilization. Here we developed a new category of organogold(III) complexes, Tp-Au-1 and Tp-Au-2, through adopting a through-space interaction motif to realize high X-ray attenuation efficiency and efficient harvesting of triplet excitons for emission. Thanks to the efficient through-space charge transfer process, this panel of complexes achieved higher photoluminescence quantum yield and shorter radiative lifetimes compared with the through-bond reference complexes. Inspiringly, these organogold(III) complexes exhibited polarity-dependent emission origins: thermally activated delayed fluorescence and/or phosphorescence. Under X-ray irradiation, Tp-Au-2 manifested intense radioluminescence together with a record-high scintillation light yield of 77,600 photons MeV-1 for organic scintillators. The resulting scintillator screens demonstrated high-quality X-ray imaging with >16.0 line pairs mm-1 spatial resolution, outstripping most organic and inorganic scintillators. This finding provides a feasible strategy for the design of superior organic X-ray scintillators.

Photoluminescent Bi-doped CsPbX3 (X: Br, I) perovskite quantum dots for optoelectronic devices

Abstract Perovskite quantum dots (PQDs) became a hot spot in recent years due to their amazing properties, such as the high photoluminescence quantum yield, tunable emission, and narrow bandwidth being important for their application in different optoelectronic devices. In this work, Bi-doped CsPbBr3 and Bi-doped CsPbI3 PQDs were synthesized through the hot-injection method and compared with pristine CsPbBr3 and CsPbI3 to analyze the effect of Bi and the halogen on their properties. In addition, all the samples were synthesized at 130°C, 150°C, and 170°C with the aim of analyzing the effect of the temperature. The results showed a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi. Graphical abstract Impact statement We believe that the work in this article represents an important advance in the application of perovskite quantum dots in optoelectronics applications, such as in LEDs or lasers. We report here the synthesis and characterization of Bi-doped CsPbX3 perovskite quantum dots (PQDs), being X: Br and I. These Bi-doped PQDs show a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi. Therefore, they are good candidates to fabricate optoelectronic devices such as LEDs and lasers thanks to their high photoluminescence emission and their tunable emission.

Pushing the Limits: Down‐Converting Er3+‐Doped BaF2 Single Crystals with Photoluminescence Quantum Yield Surpassing 100%

AbstractDown‐conversion (DC) is a phenomenon that can enable the observation of photoluminescent quantum yield (PLQY) values exceeding 100%. A comprehensive study of the DC properties of BaF2–based single crystals with different Er3+ doping levels (1–25 mol.%) is presented. The samples exhibit a PLQY of 110% in the 1550–1650 nm under 405 nm excitation. This remarkable PLQY is attributed to a cross‐relaxation process within the energy levels of Er3+. Furthermore, when considering all emitted photons in the 1000–1650 nm range, the PLQY reaches 153% for a sample doped with 5 mol.% of Er3+. By integrating the emission of this single crystal with a Ge diode, serving as an example of a photovoltaic device sensitive to short‐wave infrared light, a significant enhancement in short‐circuit current is demonstrated. In a broader context, the presented material holds promise for improving the spectral response of low‐bandgap photovoltaic devices.

Ultra-stable and highly-bright CsPbBr3 perovskite/silica nanocomposites for miRNA detection based on digital single-nanoparticle counting

Single-nanoparticle counting (SNPC) based on fluorescent tag (FT) stands out for its capacity to achieve amplification-free and sensitive detection of biomarkers. The stability and luminescence of FT are important to the sensitivity and reliability of SPNC. In this work, we developed novel perovskite/silica nanocomposites by in-situ nanoconfined growth of CsPbBr3 nanocrystals inside mesoporous structure of silica nanoparticles. PbBr(OH) was formed in an alkaline-assisted reaction triggered by water on the surface of CsPbBr3 nanocrystals. The as-obtained nanocomposites, featuring dual protection from silica matrix and PbBr(OH), exhibited high absolute photoluminescence quantum yield (PLQY) of 86.5% and demonstrated outstanding PL stability confronting with water, heat, ultrasound and UV-irradiation, which is desired by SNPC-based biosensor. Thereafter, these nanocomposites were used to construct an operationally friendly SNPC assay for the amplification-free quantification of cancer-associated miRNA. Quantitative detection of miRNA could be accomplished by directly counting the number of nanocomposites using a flow cytometer in this assay. This strategy did not ask for multiple washing steps and demonstrated specific and sensitive detection of miRNA 21, which exhibited a dynamic range of 1–1000 pM and limit of detection of 79 amol. The employment of highly stable perovskite/silica nanocomposites improved the test reliability and stability of SNPC, revealing the vast potential of perovskites in biosensing.

Determination of carbohydrate content in kenaf degumming wastewater and converting them to carbon dots

The traditional textile degumming process produces abundant wastewater, which contains a lot of monosaccharides and oligosaccharides. It is of great economic and environmental significance to utilize these carbohydrates in high value. In this study, high performance liquid chromatography (HPLC) was used to analyze the carbohydrate components in kenaf degumming wastewater, and then the production of C-dots using the wastewater was explored. The results showed that the types and content in the degumming wastewater were monosaccharides (glucose, xylose and arabinose) and oligosaccharides (dextran, xylan and araban). The carbohydrate (mainly glucan and xylan) content in wastewater accounted for 91.16 % of the total carbohydrates weight loss in kenaf degumming process. By using hydrolysis and hydrothermal reaction on kenaf degumming wastewater, blue-green carbon dots (C-dots) with good performance were prepared and successfully applied to anti-counterfeiting printing. In particular, the as-prepared C-dots prepared from kenaf degumming wastewater with urea added (WUC-dots) showed an excitation-dependent photoluminescence (PL) spectrum and quantum yield (QY) of 2.4 % in aqueous solution. The fluorescent code exhibited a clear outline, excitation-tunable color and good stability, showing a great potential for anti-counterfeiting system.

Pseudohalogen Ammonium Salt-Assisted Syntheses of Large-Sized Indium Phosphide Quantum Dots with Near-Infrared Photoluminescence.

The development of indium phosphide (InP)-based quantum dots (QDs) with a near-infrared (NIR) emission area still lags behind the visible wavelength region and remains problematic. This study describes a one-step in situ pseudohalogen ammonium salt-assisted approach to generate NIR-emitted InP-based QDs with high photoluminescence quantum yields (PLQYs). The coexistence of NH4+ and PF6- ions from NH4PF6 may in situ synchronously etch and passivate the surface oxides and impede the creation of traps under the whole growth process of InP QDs. Experimental findings demonstrated that the in situ pseudohalogen ammonium salt-assisted syntheses technique may feature emission at a full width at half-maximum (fwhm) peak as fine as ∼45 nm and broaden the emission range to around ∼780 nm. A two-step approach for ZnS shells was developed to further improve the PLQY of NIR-emitted InP QDs. Furthermore, the constructed high-power intrinsically stretchable NIR color-conversion film employing the InP-based QDs/polymer composites presented excellent luminescence conversion ability and stretchability.

Synchronously Polishing the Lead-Rich Surface and Passivating Surface Defects of CsPb(Br/I)3 Quantum Dots for High-Performance Pure-Red PeLEDs.

Mixed-halide CsPb(Br/I)3 perovskite quantum dots (QDs) are regarded as one of the most promising candidates for pure-red perovskite light-emitting diodes (PeLEDs) due to their precise spectral tuning property. However, the lead-rich surface of these QDs usually results in halide ion migration and nonradiative recombination loss, which remains a great challenge for high-performance PeLEDs. To solve the above issues, we employ a chelating agent of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid hydrate (DOTA) to polish the lead-rich surface of the QDs and meanwhile introduce a new ligand of 2,3-dimercaptosuccinic acid (DMSA) to passivate surface defects of the QDs. This synchronous post-treatment strategy results in high-quality CsPb(Br/I)3 QDs with suppressed halide ion migration and an improved photoluminescence quantum yield, which enables us to fabricate spectrally stable pure-red PeLEDs with a peak external quantum efficiency of 23.2%, representing one of the best performance pure-red PeLEDs based on mixed-halide CsPb(Br/I)3 QDs reported to date.

Dynamic Reversible Full‐Color Piezochromic Fluorogens Featuring Through‐Space Charge‐Transfer Thermally Activated Delayed Fluorescence and their Application as X‐Ray Imaging Scintillators

AbstractThermally activated delayed fluorescence (TADF) emitters featuring through‐space charge transfer (TSCT) can be excellent candidates for piezochromic luminescent (PCL) materials due to their structural dynamics. Spatial donor‐acceptor (D−A) stacking arrangements enable the modulation of inter‐ and intramolecular D−A interactions, as well as spatial charge transfer states, under varying pressure conditions. Herein, we demonstrate an effective approach toward dynamic reversible full‐color PCL materials with TSCT‐TADF characteristics. Their single crystals exhibit a full‐color‐gamut PCL process spanning a range of 170 nm. Moreover, the TSCT‐TADF‐PCL emitters display a unity photoluminescence quantum yield, and show promising application in X‐ray scintillator imaging.

Comment on “High‐Efficient Blue Emission and Bandgap Engineering from Jahn‒Teller Distorted Halide Double Perovskites”

AbstractIn a recent publication, Liu et al. investigated the doping strategy of pentavalent antimony (Sb5+) in the benchmark material Cs2NaInCl6, achieving a bright blue emission with a high photoluminescence quantum yield of ≈90% at low doping concentrations and bandgaps as low as 1.24 eV at high doping concentrations (Adv. Opt. Mater. 2024, 12, 2301576). In this comment, by reanalyzing Liu et al.' data and conducting hybrid density functional theory calculations, the study provides evidence supporting the incorporation of Sb3+ ions rather than “Sb5+ ions”, as the cause of the efficient blue emission observed in the lightly‐doped Cs2NaInCl6 samples. Furthermore, it is proposed that the narrowing of the bandgap in the “heavily‐doped Cs2NaInCl6” samples is a result of the formation of a new phase related to a mixed‐valence salt, Cs4SbIIISbVCl12.

Dynamic Reversible Full-Color Piezochromic Fluorogens Featuring Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence and their Application as X-Ray Imaging Scintillators.

Thermally activated delayed fluorescence (TADF) emitters featuring through-space charge transfer (TSCT) can be excellent candidates for piezochromic luminescent (PCL) materials due to their structural dynamics. Spatial donor-acceptor (D-A) stacking arrangements enable the modulation of inter- and intramolecular D-A interactions, as well as spatial charge transfer states, under varying pressure conditions. Herein, we demonstrate an effective approach toward dynamic reversible full-color PCL materials with TSCT-TADF characteristics. Their single crystals exhibit a full-color-gamut PCL process spanning a range of 170 nm. Moreover, the TSCT-TADF-PCL emitters display a unity photoluminescence quantum yield, and show promising application in X-ray scintillator imaging.

Achieving Seconds‐to‐Hours Duration‐Tunable Organic Long Persistent Luminescence from Carbon Dots‐Based Exciplex Systems by Energy Gaps Regulation†

Comprehensive SummaryDuration‐tunable afterglow materials have garnered considerable attention in various applications. Herein, carbon dots (CDs)‐based long persistent luminescence (LPL) composites with a tunable duration in an ultrawide range of seconds‐to‐hours levels were designed and prepared for the first time. In contrast to the established CD‐based afterglow materials, we reported that CD‐based composites exhibit LPL in the form of exciplexes and long‐lived charge‐separated states, enabling the LPL to be prolonged from several seconds to over one hour, exceeding the typical regulation range (limited to 1 min). Further studies revealed that the relationship between the excited and charge‐transfer states of CDs plays a pivotal role in activating the LPL and regulating its duration. Furthermore, these composites exhibited high photoluminescence (PL) quantum yields of up to 60.63%, and their LPL was robust under ambient conditions, even in aqueous media. Their robust and superior LPL performance endows these composites with a strong competitive advantage in dynamic display systems, such as tags for time‐resolved data encryption and displays of the remaining time of takeaways. This study offers an approach to preparing CDs‐based LPL composites with tunable durations and may provide new insights for the development of rare‐earth‐free LPL materials.

White Light Emission via Dual Thermally Activated Delayed Fluorescence from a Single-Component Phenothiazines-Diphenyl Quinoline Conjugate.

White light emission (WLE) via dual thermally activated delayed fluorescence (TADF) from a single-component-based organic system remains challenging as a result of the difficulty in design. Here, we introduce a conformational isomerization approach to achieve WLE from a twisted donor-acceptor (PTzQP1) that comprises two phenothiazines covalently attached to the 6,8-isomeric positions of 2,4-diphenyl quinoline via two C-N single bonds. Spectroscopic studies and quantum chemistry calculations revealed that PTzQP1 shows WLE via simultaneous blue TADF and orange TADF covering the visible range (420-800 nm) with a photoluminescence quantum yield of 45 ± 2% and Commission Internationale de l'Éclairage (CIE) coordinates of 0.30, 0.33. The dual TADF features with high rates of reverse intersystem crossing (kRISC1 = 1.38 × 107 ± 0.24 s-1 and kRISC2 = 5.04 × 106 ± 0.32 s-1) are realized as a result of the low singlet-triplet gaps (S1EQ-T1EQ = 0.04 eV and S1QA-T1QA = 0.05 eV) of the quasi-axial (QA) and quasi-equatorial (QE) conformers. This finding is expected to provide a new direction for designing high-energy-efficient WLE emitters.

Efficient Circularly Polarized Luminescence and Bright White Emission from Hybrid Indium‐Based Perovskites via Achiral Building Blocks

AbstractChiral organic‐inorganic hybrid perovskites (OIHPs) exhibit exceptional optical and chiral properties, demonstrating potential for 3D display, circularly polarized light‐emitting diodes (CP‐LEDs), and CPL switches. However, the construction of chiral OIHPs often relies on chiral building blocks, limiting chemical diversity, and possessing challenges in achieving large asymmetry factor (glum) without sacrificing photoluminescence quantum yield (PLQY). Here, Chiral DMA4In1‐xSbxCl7 (DMA = dimethylammonium, x = 0 to 1) with superior circularly polarized luminescence (CPL) are successfully constructed based on achiral building blocks DMA+ and metal halides. By optimizing the Sb3+ content, bright white emission with a high PLQY of 69.13% is achieved, as well as near‐unity PLQY yellow emission and strong CPL signals with a glum of up to +1.40 × 10−2, exhibiting a performance comparable to state‐of‐the‐art chiral OIHPs. Combining optical characterizations and theoretical calculations reveal that these intriguing properties originate from the intrinsic chiral helical structures and a pair of perfect complementary color emissions in DMA4In1‐xSbxCl7. In addition, DMA4In1‐xSbxCl7 exhibit excellent thermal stability and mild thermal quenching in the temperature range of 300 to 420 K. These fascinating properties suggest that DMA4In1‐xSbxCl7 have significant applications in white light‐emitting diodes (WLED), 3D displays and anti‐counterfeiting.

Extremely Enhanced Photoluminescence in MoS2-Derived Quantum Sheets.

Molybdenum disulfide (MoS2) quantum sheets (QSs) are attractive for applications due to their tunable energy band structures and optical and electronic properties. The photoluminescence quantum yield (PLQY) of MoS2 QSs achieved by mechanical and liquid exfoliation and chemical vapor deposition is low. Some studies have reported that chemical treatment and elemental doping can improve the PLQY of transition metal dichalcogenides (TMDs), but this is limited by complex instruments and reactions. In this study, a heat treatment method based on a polar solvent is reported to improve the PLQY and photoluminescence (PL) intensity of MoS2 QSs at room temperature. The absolute PLQY of treated MoS2 QSs is increased to 18.5%, and the PL intensity is increased by a factor of 64. This method is also effective for tungsten disulfide (WS2) QSs. The PL enhancement of QSs is attributed to oxidation of the edges. Such passivation/deformation of MoS2 QSs facilitates the radiative route rather than the nonradiative route, resulting in extreme enhancement of the PL. Our work could provide novel insights/routes toward the PL enhancement of TMD QSs.

Conjugated Zwitterionic Oligomers as Ligands on Perovskite Nanocrystals: Hybrid Structures with Tunable Interparticle Spacing.

Conventional ligands for CsPbBr3 perovskite nanocrystals (NCs), composed of polar, coordinating head groups (e.g., ammonium or zwitterionic) and aliphatic tails, are instrumental in stabilizing the NCs against sintering and aggregation. Nonetheless, the aliphatic (insulating) nature of these ligands represents drawbacks with respect to objectives in optoelectronics, and yet removing these ligands typically leads to a loss of colloidal stability. In this paper, we describe the preparation of CsPbBr3 NCs in the presence of discrete conjugated oligomers that were prepared by an iterative synthetic approach and capped at their chain ends with sulfobetaine zwitterions for perovskite coordination. Notably, these zwitterionic oligofluorenes are compatible with the hot injection and ligand exchange conditions used to prepare CsPbBr3 NCs, yielding stable NC dispersions with high photoluminescence quantum yields (PLQY, >90%) and spectral features representative of both the perovskite core and conjugated ligand shell. Controlling the chain length of these capping ligands effectively regulated inter-NC spacing and packing geometry when cast into solid films, with evidence derived from both transmission electron microscopy (TEM) and grazing incidence X-ray scattering measurements.

Aqueous synthesis of photoluminescence enhanced CuInS2/ZnS quantum dots via the facile hot injection growth of AgInS2 interlayer

In this study, the hot injection of Ag ions to enhance the PL performance of aqueous-phase CuInS2/ZnS quantum dots (QDs) via the formation of AgInS2 interlayer is first developed. Different amount of Ag doping by hot injection realizes the precise tuning of the peak wavelength from 649 nm to 684 nm, while the photoluminescence quantum yield is also improved from 14.79% to 26.8% due to the formation of the AgInS2 interlayer on the surface of CuInS2 QDs. The results of various characterizations demonstrate the formation of AgInS2 interlayer and explain the enhanced PL performance of CuInS2 QDs. This will expand the understanding of the PL enhancement of the aqueous-phase CuInS2/ZnS QDs and solidify the foundation for subsequent practical research to further realize the potential of aqueous CuInS2 QDs.