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Increasing photoluminescence quantum yield by nanophotonic design of quantum-confined halide perovskite nanowire arrays
摘要： High photoluminescence quantum yield (PLQY) is required to reach optimal performance in solar cells, lasers and light-emitting diodes (LEDs). Typically, PLQY can be increased by improving the material quality to reduce the non-radiative recombination rate. It is in principle equally effective to improve the optical design by nanostructuring a material to increase light out-coupling efficiency and introduce quantum confinement, both of which can increase the radiative recombination rate. However, increased surface recombination typically minimizes nanostructure gains in PLQY. Here a template guided vapor phase growth of CH3NH3PbI3 (MAPbI3) nanowire (NW) arrays with unprecedented control of NW diameter from the bulk (250 nm) to the quantum confined regime (5.7 nm) is demonstrated, while simultaneously providing a low surface recombination velocity of 18 cm s-1. This enables a 56-fold increase in the internal PLQY, from 0.81 % to 45.1 %, and a 2.3-fold increase in light out-coupling efficiency to increase the external PLQY by a factor of 130, from 0.33 % up to 42.6 %, exclusively using nanophotonic design.
关键词： light out-coupling,photoluminescence quantum yield,quantum confinement,perovskite,photodetector
更新于2025-11-14 15:28:36
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Excellent exciton luminescence of CsPbI3 red quantum dots in borate glass
摘要： We have fabricated CsPbI3 perovskite quantum dots in a borate glass by melt-quenching technique. Three representative samples with different treatment conditions are investigated. As treatment condition enhances, energy gap is extracted as 1.75-1.76eV, and photoluminescence peak is adjustable from 675 to 691nm. Full width at half-maximum (FWHM) varies from 43 to 37 nm. PL intensity first increases and then decreases with increasing excitation wavelength, but the peak wavelength and line-shape are independent. High PLQY values of 23.8%-61.4% are obtained. The high PLQY values are attributed to good crystal quality and less energy dissipation. PL lifetime is fitted as 24.0-28.2ns and 100.2-123.0ns for short and long lifetime components in bi-exponential function. For temperature from 25 to 125 oC, PL intensity decreases, but it is reversible. Exciton binding energy is extracted in the level of 375-454meV. The FWHM broadening from 39 to 49nm and peak blue-shift from 690 to 685nm are investigated.
关键词： Photoluminescence quantum yield,Lifetime,CsPbI3,Temperature dependence,Quantum dots glass,Exciton
更新于2025-11-14 15:23:50
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Blue Electrogenerated Chemiluminescence from Halide Perovskite Nanocrystals
摘要： Electrogenerated chemiluminescence (ECL) has been extensively used in ultrasensitive electroanalysis because it can be generated electrochemically without using expensive optics and light sources. Visible ECL emission can be obtained with a reasonable quantum yield and stability. Blue ECL is rare and often suffers from stability and poor quantum efficiency. Blue ECL emission at 473 nm from organometallic halide perovskite nanocrystals (PNCs), CH3NH3PbCl1.08Br1.92, is reported here for the first time using tripropylamine (TPrA) as co-reactant. The blue ECL emission peak resembles its photoluminescence peak position. In addition to this blue emission peak, the ECL spectra of CH3NH3PbCl1.08Br1.92 PNCs also showed a broad ECL peak at 745 nm. Generation of the second ECL peak at 745 nm from CH3NH3PbCl1.08Br1.92 PNCs was can be explained by the existence of surface trap states on as-synthesized PNC due to incomplete surface passivation. Halide anion tunability of ECL emission from CH3NH3PbX3 (X: Cl, Br, I) PNCs is also demonstrated. The fluorescence microscopy image of single PNC and stability of selected single PNCs are presented in this with simultaneous acquisition of fluorescence spectra using 405-nm laser excitation. The photoluminescence (PL) decay was described by PL lifetime (τ) of 1.2 ns. The effect of the addition of surfactants (oleic acid and n-octylamine) on the fluorescence intensity and stability of CH3NH3PbCl1.08Br1.92 PNCs is also discussed.
关键词： Surfactants,Blue light emission,ECL (electrogenerated chemiluminescence),Photoluminescence (PL),Perovskite nanocrystals (PNCs),Photoluminescence quantum yield (PLQY)
更新于2025-09-23 15:23:52
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Broadband Emission in Hybrid Organic–Inorganic Halides of Group 12 Metals
摘要： We report syntheses, crystal and electronic structures, and characterization of three new hybrid organic?inorganic halides (R)ZnBr3(DMSO), (R)2CdBr4·DMSO, and (R)CdI3(DMSO) (where (R) = C6(CH3)5CH2N(CH3)3, and DMSO = dimethyl sulfoxide). The compounds can be conveniently prepared as single crystals and bulk polycrystalline powders using a DMSO?methanol solvent system. On the basis of the single-crystal X-ray diffraction results carried out at room temperature and 100 K, all compounds have zero-dimensional (0D) crystal structures featuring alternating layers of bulky organic cations and molecular inorganic anions based on a tetrahedral coordination around group 12 metal cations. The presence of discrete molecular building blocks in the 0D structures results in localized charges and tunable room-temperature light emission, including white light for (R)ZnBr3(DMSO), bluish-white light for (R)2CdBr4·DMSO, and green for (R)CdI3(DMSO). The highest photoluminescence quantum yield (PLQY) value of 3.07% was measured for (R)ZnBr3(DMSO), which emits cold white light based on the calculated correlated color temperature (CCT) of 11,044 K. All compounds exhibit fast photoluminescence lifetimes on the timescale of tens of nanoseconds, consistent with the fast luminescence decay observed in π-conjugated organic molecules. Temperature dependence photoluminescence study showed the appearance of additional peaks around 550 nm, resulting from the organic salt emission. Density functional theory calculations show that the incorporation of both the low-gap aromatic molecule R and the relatively electropositive Zn and Cd metals can lead to exciton localization at the aromatic molecular cations, which act as luminescence centers.
关键词： zero-dimensional structures,broadband emission,group 12 metals,exciton localization,photoluminescence quantum yield,hybrid organic?inorganic halides
更新于2025-09-23 15:23:52
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Reducing aggregation caused quenching effect through co-assembly of PAH chromophores and molecular barriers
摘要： The features of well-conjugated and planar aromatic structures make π-conjugated luminescent materials suffer from aggregation caused quenching (ACQ) effect when used in solid or aggregated states, which greatly impedes their applications in optoelectronic devices and biological applications. Herein, we reduce the ACQ effect by demonstrating a facile and low cost method to co-assemble polycyclic aromatic hydrocarbon (PAH) chromophores and octafluoronaphthalene together. Significantly, the solid photoluminescence quantum yield (PLQYs) for the as-resulted four micro/nanococrystals are enhanced by 254%, 235%, 474 and 582%, respectively. Protection from hydrophilic polymer chains (P123 (PEO20-PPO70-PEO20)) endows the cocrystals with superb dispersibility in water. More importantly, profiting from the above-mentioned highly improved properties, nano-cocrystals present good biocompatibility and considerable cell imaging performance. This research provides a simple method to enhance the emission, biocompatibility and cellular permeability of common chromophores, which may open more avenues for the applications of originally non- or poor fluorescent PAHs.
关键词： cocrystals,aggregation caused quenching,bioimaging,polycyclic aromatic hydrocarbon,photoluminescence quantum yield
更新于2025-09-23 15:23:52
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Achieving Near-Unity Photoluminescence Efficiency for Blue-violet Emitting Perovskite Nanocrystals
摘要： While the perovskite nanocrystals (NCs) have shown great promise as materials for efficient light emitting diodes (LEDs), low photoluminescence quantum yield (PLQY) of the blue-emitting perovskites is an impediment to the development of white LEDs of which blue is an essential component. Herein, we report that room temperature post-synthetic treatment of weakly blue-violet emitting (PLQY 3%) CsPbCl3 NCs with CdCl2 results in an instantaneous enhancement of the PLQY to near-unity without affecting the PL peak position (406 nm) and spectral width. The time-resolved PL and ultrafast transient absorption measurements confirm the removal of nonradiative defect states of the CsPbCl3 NCs in treated sample. The elemental composition and structural data of the treated sample reveal facile doping of Cd2+ into the crystal lattice without affecting the size and shape of the NCs. Extraordinary PLQY, high air- and photo-stability and ease of preparation of this Cd-doped CsPbCl3 make it by far the most attractive blue-emitting perovskite for development of efficient blue and white LEDs.
关键词： photoluminescence quantum yield,blue-emitting perovskites,perovskite nanocrystals,CdCl2 treatment,white LEDs
更新于2025-09-23 15:21:21
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Highly Efficient and Stable CsPbBr3 Perovskite Quantum Dots by Encapsulating in Dual-Shell Hollow Silica Spheres for WLEDs
摘要： Poor stability of CsPbX3 (X = Cl, Br or I) perovskite quantum dots (QDs) has greatly hindered their practical photoelectric applications, and how to improve it still remains a critical challenge. Herein, we encapsulated the CsPbBr3 QDs into a dual-shell hollow silica (SiO2) spheres via a simple successive ionic layer adsorption and reaction (SILAR) method. The hierarchical dual-shell structures permit CsPbBr3 QDs to be anchored on the interior of the SiO2 spheres while keeping the outside surface undisturbed, which can protect CsPbBr3 QDs from direct exposure to the atmosphere. Due to the comprehensive protection of dual-shell hollow SiO2 spheres, the CsPbBr3/SiO2 nanospheres exhibit markedly enhanced stability against light and heat, with residual PL intensity of 89% after continuous exposure of 72 h to UV light and 65% at 100?C heat treatment, respectively. In addition, an optimal PLQY of 89% is obtained with suppressed nonradiative recombination. Finally, the fabricated white light-emitting diodes (LEDs) device by employing CsPbBr3/SiO2 green phosphors could achieve a wide color gamut covering up to 136% of the NTSC standard. This work provides a novel SiO2-based encapsulation approach to solve the intrinsic instability issues of CsPbBr3 QDs, which has a profound impact on their practical applications.
关键词： photoluminescence quantum yield,CsPbBr3 quantum dots,dual-shell hollow silica spheres,stability,white light-emitting diodes
更新于2025-09-23 15:21:01
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Effect of indium alloying on the charge carrier dynamics of thick-shell InP/ZnSe quantum dots
摘要： Thick-shell InP/ZnSe III–V/II–VI quantum dots (QDs) were synthesized with two distinct interfaces between the InP core and ZnSe shell: alloy and core/shell. Despite sharing similar optical properties in the spectral domain, these two QD systems have differing amounts of indium incorporation in the shell as determined by high-resolution energy-dispersive x-ray spectroscopy scanning transmission electron microscopy. Ultrafast fluorescence upconversion spectroscopy was used to probe the charge carrier dynamics of these two systems and shows substantial charge carrier trapping in both systems that prevents radiative recombination and reduces the photoluminescence quantum yield. The alloy and core/shell QDs show slight differences in the extent of charge carrier localization with more extensive trapping observed in the alloy nanocrystals. Despite the ability to grow a thick shell, structural defects caused by III–V/II–VI charge carrier imbalances still need to be mitigated to further improve InP QDs.
关键词： indium alloying,InP/ZnSe,charge carrier dynamics,photoluminescence quantum yield,quantum dots
更新于2025-09-23 15:21:01
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Ancillary ligand increases the efficiency of heteroleptic Ir-based triplet emitters in OLED devices
摘要： The excellent contrast ratio, visibility, and advantages in producing thin and light displays let organic light emitting diodes change the paradigm of the display industry. To improve future display technologies, higher electroluminescence efficiency is needed. Herein, the detailed study of the non-radiative decay mechanism employing density functional theory calculations is carried out and a simple, general strategy for the design of the ancillary ligand is formulated. It is shown that steric bulk properly directed towards the phenylisoquinoline ligands can significantly reduce the non-radiative decay rate.
关键词： photoluminescence quantum yield,non-radiative decay,OLED,Ir(III)-complexes,density functional theory
更新于2025-09-23 15:21:01
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Cyclometalated Ir(III) Complexes Towards Blue-Emissive Dopant for Organic Light-Emitting Diodes: Fundamentals of Photophysics and Designing Strategies
摘要： The main difficulties hindering development of a deep-blue phosphorescent cyclometalated Ir(III) complex are insufficient colour purity, i.e., failure to achieve ideal Commission Internationale de L’Eclairage (CIE) coordinates of (0.14, 0.09), and insufficient emission efficiency and stability. The latter problem is due to the highly energetic and hot excited states of these complexes, which yield faster decomposition. Therefore, control of the excited-state properties of cyclometalated Ir(III) complexes through systematic chemical modification of the ligands is being extensively investigated, with the aim of developing efficient and stable blue phosphorescent materials. The most common strategies towards achievement of a blue phosphorescent cyclometalated Ir(III) complex involve 1) substitution of electron-withdrawing F atoms at the cyclometalating ligands that stabilise the HOMO orbitals and 2) use of a heteropeltic system with electron-rich ancillary ligands bearing a 5-membered ring heterocycle to increase the LUMO energy level. However, the C–F bonds on the cyclometalating ligands have been found to be inherently unstable during device operation; thus, other types of electron-withdrawing groups (e.g., the cyano, trifluoromethyl, and sulfonyl groups) have been applied. Along with phosphorescence colour tuning to blue, the influence of the ligand structure on the photoluminescence quantum yield (PLQY) is also being intensively investigated. Two major PLQY lowering mechanisms for blue emissive Ir(III) complexes have been identified: 1) the vibronic-coupled non-radiative decay process and 2) crossing from the emissive state to an upper non-emissive 3MC excited state. To enhance the PLQY, mechanism 1) can be suppressed by employing rigid ligand frameworks to restrict intramolecular motion, whereas mechanism 2) can be prevented by destabilising the 3MC state using strong σ donor ligands such as N-heterocyclic carbenes. This review summarises the fundamental photophysics of cyclometalated Ir(III) complexes and surveys design strategies for efficient blue phosphorescent Ir(III) complexes, to provide a guide for future research in this field.
关键词： blue phosphorescent,3MC excited state,photoluminescence quantum yield,non-radiative decay,N-heterocyclic carbenes,cyclometalated Ir(III) complexes,OLEDs
更新于2025-09-23 15:21:01