Time-resolved Photoluminescence Research Articles

Amplified Detection of Threading Dislocations in n-Type 4H-SiC Epilayers Enabled by Time-Resolved Photoluminescence Mapping.

Threading dislocations (TDs) in epitaxial layers of silicon carbide (SiC) exert a negative impact on the device performance, thereby hampering the commercialization of SiC power devices. Therefore, inspection of TD defects is a crucial step in the fabrication of SiC wafers. In this work, we reported a time-resolved photoluminescence (PL) mapping technique for detecting TDs by extracting PL images at different delay times after pulse excitation along the lifetime decay curve. The results indicate a 2-fold enlargement of the TD PL quenching spot at a later delay time compared to the full delay time, enhancing the precision of TD defect imaging in 4H-SiC epitaxial layers. We postulate that our time-resolved PL mapping technique holds promise for the industrial evaluation of TD defects in SiC epitaxial layers.

Revealing the Dynamic Aspects of Photoinduced Halide Segregation in Mixed-Halide Cs0.15FA0.85PbI2Br Perovskite Films Using a Hyperspectral Imaging Technique.

The band gap energy of halide perovskite semiconductors is manipulated by controlling the halide composition, and mixed halide perovskites are receiving much attention as top cell materials for tandem solar cells. To understand dynamic aspects of photoinduced halide segregation in mixed-halide perovskite films, we use a hyperspectral imaging technique. We reveal the space- and time-resolved photoluminescence (PL) spectra of Cs0.15FA0.85PbI2Br perovskite films during prolonged light illumination. Under applied electric fields, we observe photoinduced phase segregation at the excitation laser spot, with a line-shape I-rich region of low PL efficiency appearing near the anode electrode. This I-rich region moves from the anode to the cathode electrodes and stops at the laser excitation spot. We discuss the significant enhancement of halide ion migration under light illumination and the dynamical changes of photoinduced halide segregation.

Highly Efficient and Thermally Stable Ultra-Broadband NIR-II Emtting Li(Ga, Al)5O8:Cr3+, Ni2+ Phosphors for Spectroscopy Analysis.

Near-infrared (NIR) spectroscopy has diverse applications across various fields, such as the detection of food components and pesticide residues, early diagnosis, and treatment of cancer. In this work, a series of optimized LiAl5-xGaxO8:0.1Ni2+ (x = 0-5) ultrabroadband NIR-II luminescent systems are developed. The density functional theory (DFT) calculations, time-resolved photoluminescence (TRPL) spectroscopy, and 77 K PL spectra demonstrate that the substitution of Ga3+ for Al3+ creates more favorable sites for Ni2+ luminescence and enhances structural orderliness while reducing the number of luminescent centers. This leads to a red shift in the emission peak from 1177 to 1252 nm with a 14-fold increase in luminescence intensity. At 375 K, thermal stability increases from 81% (x = 0) to 90% (x = 5) compared to 300 K. Subsequent co-doping with Cr3+ results in an excitation peak with a red shift into the blue-violet region (420 nm), accompanied by a notable enhancement in absorption efficiency (AE) and an increase in external quantum efficiency (EQE) from 4% to 62%. Finally, the potential application of the prepared phosphors in both qualitative and quantitative analysis of organic compounds is demonstrated, which will offer new insights for the design and synthesis of ultrabroadband NIR-II light sources.

Efficient Greenish-Blue Thermally Activated Delayed Fluorescence Zn Complex for Organic Light Emitting Devices

A greenish-blue zinc complex Zn(PhOBz)-PXZ with enhanced thermally activated delayed fluorescence (TADF) properties has been prepared from Zn(OAc)2 and 4PXZ2OHBz, a 2-(1H-benzimidazol-2-yl)phenol-based TADF ligand. The TADF phenomenon has been confirmed by time-resolved photoluminescence (TrPL) studies. The DFT calculations show spatially well-separated HOMO and LUMO in their ground states, along with a small energy splitting between the excited singlet (S1) and triplet (T1) states, in a good agreement with the TADF mechanism. Due to the high thermal stability of Zn(PhOBz)-PXZ, OLED devices can be fabricated by vacuum vapor deposition, and greenish-blue OLEDs with the maximum emission at 521 nm were successfully demonstrated. The maximum external quantum efficiency (EQEmax) of 10.6%, with Commission Internationale de l’Eclairage (CIE) coordinates of (0.28, 0.47) were recorded. Zinc TADF complexes have the advantages of cost-effectiveness, greater abundance of natural resources, environmentally friendly metals, making them potential replacements for future precious metal emitters.

Photoresponsive Luminescent Silica Nanoparticles as Additive for 3D Printing and Electrospinning.

In this study, we present the synthesis and a versatile way to incorporate photoresponsive organic luminophores into polymeric materials using mesoporous silica nanoparticles (MSNs). The encapsulated thioethers within the MSNs were employed in polyvinyl alcohol (PVA) films, resin-based stereolithography, and electrospinning. Due to light-induced cyclization to dibenzothiophenes (DBTs), mmOC12 loaded materials were used to inscribe images using UV light. The DBTs formed from mmOC12 (mmDBTA/B) exhibit a long phosphorescence afterglow, which was investigated by steady-state and time-resolved photoluminescence spectroscopy. In addition, scanning electron microscopy (SEM) imaging, including energy dispersive X-ray spectroscopy (EDX), revealed the well-dispersed and intact MSNs in the polymeric materials. This approach shows a general way to incorporate non-polar organic luminophores into polymeric materials while retaining their unique emission properties.

Time-resolved exciton photoluminescence and its linear polarization of an ensemble of CdSe/CdS colloidal nanoplatelets

We present experimental and theoretical studies of the time-resolved photoluminescence and its linear polarization of an ensemble of CdSe/CdS colloidal nanoplatelets in the Faraday magnetic fields up to 6 T. The linearly polarized photoluminescence kinetics stems from the excitons resonantly excited with the linearly polarized light pulse and comprises both the structural contribution and the exciton optical alignment effect. The emission from the bright and dark exciton states is distinguished by their different intensity decay timescales with lifetime at cryogenic temperature of about 1–2ns and 100–200ns, respectively. The longitudinal spin relaxation time of the bright exciton was determined to be from 4 to 6ns depending on the magnetic field. The dark exciton spin relaxation time was estimated to be in the order of 20 to 100ns. The developed theory for the bright exciton polarization kinetics and the modeling of the data allowed us to conclude that spin dephasing times of the bright as well as of the dark exciton are shorter than 0.3ns. The origin of such a strong spin relaxation time anisotropy in the ensemble of nanoplatelets is discussed.

Eu3+- activated Sr2GdF7 colloid and nano-powder for horticulture LED applications

A series of multifunctional Sr2Gd1-xEuxF7 (x = 0, 0.05, 0.10, 0.40, 0.60. 0.80, and 1.00) phosphors in stable colloidal form and as nanopowders have been prepared using a hydrothermal method. Powder X-ray diffraction analysis confirmed that the materials crystallize in a cubic crystal structure. Transmission electron microscopy shows quasi-spherical nanoparticles with an average particle size of ∼24 nm. Photoluminescence measurements show highly efficient red emission in both colloids and nanopowders, with intensity continually increasing up to 80 mol% of Eu3+ content without concentration quenching. The most prominent emission peaks are around 600 nm (orange/red) and 700 nm (deep red), with the latter more pronounced. Quantum efficiency follows a similar trend, and reaches 60 % for the sample with 80 mol% of Eu3+ content. In addition, similar asymmetry ratio values and CIE coordinates show that there is not a big change in the local symmetry around Eu3+ ions or emission color across the series. This confirms that Eu3+ resides in the same crystalline environment in samples. The observed 5D0-level lifetimes gradually decrease from 12.0 ms to 6.9 ms as the Eu3+ concentration increases. Judd-Ofelt parameters show slight variation with Eu3+ concentration with Ω4 always larger than Ω2. The temperature-dependent steady-state and time-resolved photoluminescence measurements demonstrate high stability of nanopowders’ emission up to 100 °C. The combination of temperature stability and high efficiency of emission, as well as the untypical dominant deep-red emission at 700 nm labels these nanoparticles as potential nanophosphors for various applications.

Ru-doped Aurivillius phase perovskites Bi4Ti3O12 for boosting photo-redox of N2 in photocatalytic nitrogen fixation

In this study, we prepared layered Aurivillius phase bismuth titanate perovskite oxide (Bi4Ti3O12, BT) using the sol–gel method and doped them with various amounts of Ru (BT-Rux, x = 0.05, 0.1, 0.25, and 0.5 % w/w) for photocatalytic nitrogen fixation in the absence of a sacrificial reagent. Among the prepared photocatalysts, BT-Ru0.25 showed the highest NH4+ formation rate of 119 μmolgcat−1 h−1, which is a 3.21-fold higher than BT. The Rietveld refinement X-ray diffraction results suggest that the expansion of the a and b lattice parameters of BT occurs with adding Ru, which correlates with the photocatalytic NH4+ production performance. This is because the expansion of a and b lattices of BT via Ru doping contributed to the increase in oxygen vacancies and the altered surface charge density in the Bi and Ti of BT, creating an asymmetric coordination environment that could induce the polarization of N2. Photoluminescence and Time-resolved photoluminescence analyses showed that the doping of Ru on BT reduced the recombination efficiency of the photogenerated electron-hole pairs and prolonged the electron decay time. In linear sweep voltammetry and Tafel analyses showed that Ru doping of BT suppressed the HER and photocorrosion. In-situ surfaced enhanced Raman spectroscopy (SERS) analysis revealed that the doping of Ru in BT improved the N2 interaction on the Bi-O bonds, accelerating the surface nitrogen oxidation reaction (NOR) to form NO3– and further undergoing a nitrate reduction reaction (NORR) for NH4+ production. This study highlights the importance of incorporating Ru into perovskite oxides to improve the separation of photogenerated carriers in photocatalytic NH4+ production without sacrificial reagents.

Atomic layer deposition of ultrathin nitride films for enhanced carrier lifetimes and photoluminescence in CdTe/MgCdTe double heterostructures

This work evaluates the passivation effectiveness of ultrathin nitride layers (SiNx, AlN, and TiN) deposited via atomic layer deposition on CdTe/MgCdTe double heterostructures for solar cell applications. Time-resolved photoluminescence and photoluminescence measurements revealed enhanced carrier lifetimes and reduced surface recombination, indicating improved passivation effectiveness. These results underscore the potential of SiNx as a promising passivation material to improve the efficiency of CdTe solar cells.

Carbon Nanotube-Phenyl Modified g-C3N4: A Visible Light Driven Efficient Charge Transfer System for Photocatalytic Degradation of Rhodamine B.

In this study, we report the synthesis and characterization of a novel photocatalyst composite composed of functionalized carbon nanotubes (f-CNT) and phenyl-modified graphitic carbon nitride (PhCN). The incorporation of the phenyl group extends the absorption range into the visible spectrum compared to pure g-C3N4. Additionally, the formation of the heterostructure in the f-CNT/PhCN composite exhibits improved charge transfer efficiency, facilitating the separation and transfer of photogenerated electron-hole pairs and reducing recombination rates. The photocatalytic performance of this composite was evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. The f-CNT/PhCN composite exhibits remarkable efficiency in degrading RhB, achieving 60% degradation after 4 h, and 100% after 24 h under low-power white LED excitation. This represents a substantial improvement over the non-functionalized CNT/PhCN composite, which shows much lower performance. In contrast, pure PhCN demonstrates very little activity. Structural and optical properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and UV-Vis spectroscopy. Time-resolved photoluminescence measurements were used to study the behavior of photoexcited carriers, confirming that the composite improves charge transfer efficiency for photogenerated carriers by approximately 30%. The results indicate that the functionalization of CNTs significantly enhances the photocatalytic properties of the composite, making f-CNT/PhCN a promising candidate for environmental remediation applications, particularly in the degradation of organic pollutants in wastewater.

Optical performance and luminescence properties of Dy3+-doped LaMgB5O10 phosphors

Despite significant advancements in borate-based phosphors, improving luminescent efficiency and thermal stability, particularly at high temperatures, remains a persistent challenge. In this study, Dy3+-doped LaMgB5O10 (LMBO) phosphors were synthesized and characterized for their photoluminescent properties to address these issues. Under 344 nm excitation, the Dy3+-activated LMBO phosphors exhibited strong luminescence with characteristic peaks at 482 nm (blue), 578 nm (yellow), and 663 nm (red), corresponding to specific Dy3+ transitions. Optimal luminescence was achieved at a doping level of 2 wt% Dy3+, beyond which quenching effects reduced emission intensity. The critical quenching distance (Rc) was estimated at 24.66 Å, indicating predominant non-radiative energy transfer. Moreover, thermal quenching was reduced, with the activation energy for thermal quenching determined to be 0.1975 eV, demonstrating that the material can maintain reasonable luminescence efficiency at elevated temperatures. Time-resolved photoluminescence spectroscopy revealed multi-exponential decay behavior, indicating the presence of multiple decay processes. The average luminescence lifetimes were calculated as 632 µs for the 2 wt% Dy3+ sample and 539 µs for the 3 wt% Dy3+ sample, with a clear concentration quenching effect observed at higher dopant levels. Colorimetric analysis in the CIE 1931 color space revealed a shift toward yellow with increasing Dy3+ concentration, achieving a correlated color temperature (CCT) of 6595 K at 2 wt% Dy3+. This shift supports the material’s potential for photonic and lighting applications. These findings highlight a significant advancement in addressing the thermal stability issue in phosphor materials, making Dy3+-doped LMBO phosphors promising candidates for advanced photonic technologies.

Tunable Blue-Light-Emitting Organic-Inorganic Zinc Halides with Thermally Activated Delayed Fluorescence and Room-Temperature Phosphorescence.

Hybrid metal halides have received great interests in the field of solid-state lighting technologies due to their diverse structures and excellent emission properties. In this work, we report the synthesis and characterization of four blue-emitting zero-dimensional hybrid metal halides, namely, (2HP)2ZnCl2, (2HP)2ZnBr2, (2TP)2ZnCl2, and (2TP)2ZnBr2 (2HP = 2-hydroxypyridine, 2TP = pyridine-2-thiol). By changing the ligands and halides, a remarkable increase in the photoluminescence quantum yield of (2HP)2ZnCl2 (44.7%) compared to (2TP)2ZnBr2 (1.8%) is realized. The 2HP series features excitation-dependent emission characteristics, whereas the 2TP series does not due to the effect of a different organic ligand. Utilizing time-resolved and temperature-dependent photoluminescence spectroscopies, all four compounds exhibit both thermally activated delayed fluorescence and room-temperature phosphorescence properties. These materials have excellent ambient and thermal stabilities and are solution-processable. Our work shows the importance of carefully incorporating organic ligands with the appropriate inorganic metal center to achieve tunable emission properties.

Phenyl-C61-butyric acid methyl ester (PCBM) nanoparticle mediated boasting of photoelectrochemical and photocatalytic properties of bismuth vanadate/lead sulphide (BiVO4/PbS) composite thin-film

This work delineates the fabrication and characterization of BiVO4/PbS and BiVO4/PCBM/PbS-based composite heterostructure for visible-light-driven applications, such as pollution remediation, photoelectrochemistry (PEC), and applied bias to photoelectrochemical hydrogen generation efficiency (ABPE). The heterostructured composite was synthesized by a combination of Spin coating (for bismuth vanadate - BiVO4 thin film fabrication and PCBM deposition), and Successive Ionic Layer Absorption and Reaction -SILAR (for lead sulphide - PbS deposition) method and characterized using UV–visible Spectroscopy, time-resolved photoluminescence spectroscopy (TRPL), field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and photoelectrochemistry (PEC) analysis (PEC). The key benefit of incorporation of PCBM nanoparticles in BiVO4/PCBM/PbS was realized through 1) ∼ 70 % improvement in the photocurrent density during electrochemistry analysis, 2) ∼ 2.3 times enhancement in ABPE, and 3) ∼ 43 % enhancements in ‘rate constant’ towards photocatalytic (methylene blue) degradation compared to BiVO4/PbS. The work shows the benefits of the PCBM-conductive carbon-based electron transport layer as a bridge between two inorganic semiconductors (BiVO4 and PbS) towards enhancing fast electron separation and transport at the interface during visible light irradiation.

Z-Scheme Enabled 1D/2D Nanocomposite of ZnO Nanorods and Functionalized g-C3 N4 Nanosheets for Sustainable Degradation of Terephthalic Acid.

The urgent need to mitigate water pollution and achieve Sustainable Development Goal 14 (SDG 14)-Life below water, necessitates developing efficient and eco-friendly wastewater treatment technologies. This research addresses this challenge by photocatalytic degradation of terephthalic acid, a precursor for PET bottles using environment-friendly and biocompatible photocatalysts. The 1D/2D nanocomposite comprising zinc oxide (ZnO) nanorods and functionalized graphitic carbon nitride (Zn-TG) nanosheets were synthesized and thoroughly characterized. The nanocomposite effectively mitigated the individual drawbacks of Zn-TG agglomeration and the wide band gap of ZnO as confirmed through zeta potential and Tauc's plot studies, respectively. The synthesized nanocomposite achieved ~100 % degradation within 60 minutes, exhibiting superior kinetics (~2.5 times) compared to pristine samples. The enhanced degradation efficiency was elucidated by efficient charge carrier transfer (~5 times faster) and separation (~2 times improved) as confirmed through electrochemical impedance spectroscopy and time-resolved photoluminescence studies. The proposed Z-scheme pathway provides mechanistic insights. This proposed mechanism is supported by extensive electron paramagnetic resonance (EPR) and scavenger studies. The liquid chromatography-mass spectrometry (LC-MS) analysis confirms the formation of less toxic byproducts for ensuring that the wastewater treatment process is efficient and environmentally friendly. This research helps in developing a highly effective and sustainable wastewater treatment technology.

Deep Ultraviolet Excitation Photoluminescence Characteristics and Correlative Investigation of Al-Rich AlGaN Films on Sapphire.

AlGaN is attractive for fabricating deep ultraviolet (DUV) optoelectronic and electronic devices of light-emitting diodes (LEDs), photodetectors, high-electron-mobility field-effect transistors (HEMTs), etc. We investigated the quality and optical properties of AlxGa1-xN films with high Al fractions (60-87%) grown on sapphire substrates, including AlN nucleation and buffer layers, by metal-organic chemical vapor deposition (MOCVD). They were initially investigated by high-resolution X-ray diffraction (HR-XRD) and Raman scattering (RS). A set of formulas was deduced to precisely determine x(Al) from HR-XRD data. Screw dislocation densities in AlGaN and AlN layers were deduced. DUV (266 nm) excitation RS clearly exhibits AlGaN Raman features far superior to visible RS. The simulation on the AlGaN longitudinal optical (LO) phonon modes determined the carrier concentrations in the AlGaN layers. The spatial correlation model (SCM) analyses on E2(high) modes examined the AlGaN and AlN layer properties. These high-x(Al) AlxGa1-xN films possess large energy gaps Eg in the range of 5.0-5.6 eV and are excited by a DUV 213 nm (5.8 eV) laser for room temperature (RT) photoluminescence (PL) and temperature-dependent photoluminescence (TDPL) studies. The obtained RTPL bands were deconvoluted with two Gaussian bands, indicating cross-bandgap emission, phonon replicas, and variation with x(Al). TDPL spectra at 20-300 K of Al0.87Ga0.13N exhibit the T-dependences of the band-edge luminescence near 5.6 eV and the phonon replicas. According to the Arrhenius fitting diagram of the TDPL spectra, the activation energy (19.6 meV) associated with the luminescence process is acquired. In addition, the combined PL and time-resolved photoluminescence (TRPL) spectroscopic system with DUV 213 nm pulse excitation was applied to measure a typical AlGaN multiple-quantum well (MQW). The RT TRPL decay spectra were obtained at four wavelengths and fitted by two exponentials with fast and slow decay times of ~0.2 ns and 1-2 ns, respectively. Comprehensive studies on these Al-rich AlGaN epi-films and a typical AlGaN MQW are achieved with unique and significant results, which are useful to researchers in the field.

Enabling Fast Photoresponse in Hybrid Perovskite/MoS2 Photodetectors by Separating Local Photocharge Generation and Recombination.

Interfacing CH3NH3PbI3 (MAPbI3) with 2D van der Waals materials in lateral photodetectors can suppress the dark current and driving voltage, while the interlayer charge separation also renders slower charge dynamics. In this work, we show that more than one order of magnitude faster photoresponse time can be achieved in MAPbI3/MoS2 lateral photodetectors by locally separating the photocharge generation and recombination through a parallel channel of single-layer MAPbI3. Photocurrent (Iph) mapping reveals electron diffusion lengths of about 20 μm in single-layer MAPbI3 and 4 μm in the MAPbI3/MoS2 heterostructure. The illumination-power scaling of Iph and time-resolved photoluminescence studies point to the dominant roles of the heterostructure region in photogeneration and single-layer MAPbI3 in charge recombination. Our results shed new light on the material design that can concurrently enhance photoresponsivity, reduce driving voltage, and sustain high operation speed, paving the path for developing high-performance lateral photodetectors based on hybrid perovskites.

Modulation of the Chirality and Dynamics of Self-Assembled Nanocellulose-Chiral C-Dot Film for Chiral Sensing Applications.

The detection and sensing of chirality using chiral biomaterials are growing areas of research in advanced bioelectronics. As a result, chiral-controlled biomaterials are crucial for advancing current technologies in chiral sensing applications within biosystems. A chiral carbon dot (C-dot) modulated self-assembled emissive cellulose nanocrystal (CNC) film is developed where the chirality of the CNC film can be tempered between left-handed and right-handed chirality after being doped with chiral L/D-C-dots in CNCs (C-dot-CNC film), transferring the chirality from C-dots to CNCs. The interaction between C-dots, CNCs, and carrier dynamics is investigated using a variety of steady-state and time-resolved PL spectroscopy techniques. The chiral C-dot enhanced the protonic conductivity across the CNC via the formation of hydrogen bonds with its surface functional groups and water molecules. Further, the chiral CNC-C-dots photoelectrodes demonstrate an excellent ability to distinguish between left-handed and right-handed small molecules. These findings on the underlying mechanism of spin selectivity between chiral CNC-C-dot and chiral ligand hold promise for the development of efficient chiral-sensing electronic devices.

Enhancement of the photocatalytic efficiency of ZnO utilizing luminescent Y2O3 particles

Abstract This study explored the superior photocatalytic performance of the nanoscale zinc oxide-yttrium oxide (ZnO-Y2O3) based composite over ZnO nanoparticles (NPs). We investigated this by following the photocatalytic degradation efficiency of methylene blue (MB). The sol–gel synthesized Y2O3 and ZnO NPs were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The spectral behaviour and photocatalytic efficiency of the proposed composite were investigated by UV–vis spectrophotometry, steady-state and time-resolved photoluminescence (PL) measurements, respectively. The results indicated the successful formation of Y2O3 and ZnO nanoparticles with desirable structural properties. The photocatalytic degradation efficiency of the MB solution was evaluated for different concentrations of the counterparts of the ZnO-Y2O3 composite. In particular, the ZnO-5Y2O3-based composite showed superior photocatalytic activity after 150 min of UV irradiation, achieving 98.4% degradation of the MB solution compared to the 77% degradation achieved by pure ZnO. Although Y2O3 alone does not exhibit photocatalytic activity, its combination with ZnO significantly enhances the photocatalytic performance of ZnO. This improvement was attributed to the luminescence properties of Y2O3. By elucidating this unique mechanism, the performance of photocatalytic materials can be significantly enhanced. In our study, the improvement of the photodegradation rate constant (kapp) of ZnO from 0.009 min−1 to 0.0242 min−1 demonstrated the promising photocatalytic efficiency of the ZnO-5Y2O3 based composite, opening up exciting possibilities for further applications in environmental remediation and other fields.

Warm-White Light Emission of Lead-free CsAg2I3 Single Crystal Scintillator with a One-Dimensional Electronic Structure.

Presently, the exploration of novel inorganic lead-free perovskite scintillators has emerged as a prominent topic in the field of perovskite materials. Extensive attention has been garnered by materials such as Cs3Cu2I5 due to their notable advantage in scintillation intensity, but the response time constants in the microsecond or even millisecond range severely constrain their potential applications in scintillators. In this study, large-sized (5-6 mm) CsAg2I3 single crystals with an ultrafast warm-white light emission on a nanosecond time scale are presented. Specifically, upon X-ray excitation, the single crystal demonstrates a broad-spectrum white light emission with a color temperature as high as 5129 K, attributed to its self-trapped exciton emission. The 137Cs energy spectrum reveals that CsAg2I3 possesses an ultrafast response for γ rays with a time constant of 15 ns, which is significantly faster than that of Cs3Cu2I5. Furthermore, time-resolved photoluminescence unveils a subnanosecond component with a response time of 0.9 ns. The characteristics of ultrafast warm-white light emission exhibit the significant potential of CsAg2I3 in radiation scintillation detection and its probability of playing a pivotal role in future radiation detection technology.

Efficient Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules without Spectral Overlap.

Quantum dots (QDs) are semiconductor nanocrystals whose optical properties can be tuned by altering their size. By combining QDs with dyes we can make hybrid QD-dye systems exhibiting energy transfer (ET) between QDs and dyes, which is important in sensing and lighting applications. In conventional QDs that need a shell to passivate surface defects, ET usually proceeds through Förster resonance energy transfer (FRET) that requires significant spectral overlap between QD emission and dye absorbance, as well as large oscillator strengths of those transitions. This considerably limits the choice of dyes. In contrast, perovskite QDs do not require passivating shells for bright emission, which makes ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr3 QD-dye system to achieve efficient ET from CsPbBr3 QDs to dyes with dimethyl iminium binding groups where the close binding of dyes surface facilitates spatial wavefunction overlap. Using steady-state and time-resolved photoluminescence experiments, we demonstrate that efficient ET from CsPbBr3 to dyes with minimal spectral overlap proceeds via the Dexter exchange-type mechanism, which overcomes the conventional restriction of spectral overlap that severely limits the tunability of these systems. This approach opens new avenues for QD-molecule hybrids for a wide range of applications.