Search Results (101)

CsPbBr₃ perovskite quantum dots (QDs) have attracted significant attention for optoelectronic applications owing to their outstanding optical properties, yet achieving controlled synthesis with high stability under mild conditions remains a challenge. The room-temperature synthesis of CsPbBr₃ perovskite quantum dots using a coprecipitation method is systematically investigated in this work, with an emphasis on how the structural and optical properties of the QDs are influenced by the Br/Pb ratio and OA/OAm ratio. The findings show that controlling the Br/Pb and OA/OAm ratios can effectively influence the size, crystalline phase, and surface passivation properties of CsPbBr₃ quantum dots. The photoluminescence peak shifts blue and the bandgap widens when the Br/Pb ratio rises due to a decrease in quantum dot size. This is mainly explained by more effective surface covering by Br⁻ ions and increased quantum confinement effects. The resultant quantum dots demonstrate ideal optical performance at a Br/Pb ratio of 75 and an OA/OAm ratio of 1.5, with dense ligand coverage, superior defect passivation, and markedly improved stability under UV irradiation and in aqueous environments. Variations in the Br/Pb and OA/OAm ratios affect the binding configuration and coverage of ligands on the quantum dot surface, thereby influencing the relationship between non-radiative recombination and the quantum confinement effect. The LED fabricated with the as-synthesized high-performance quantum dots demonstrates a wide color gamut, covering 129.45% of the NTSC standard, indicating strong potential for display applications. Full article

Perovskite quantum dots (PQDs) face significant performance limitations due to surface defects, which are not sufficiently addressed by conventional single-passivation methods. We introduce a dual-passivation strategy that synergistically combines bifunctional ligand 3-(N,N-dimethyloctadecylammonium)-propanesulfonate (SB3-18) treatment with silica coating to simultaneously passivate undercoordinated Pb²⁺ ions and bromine vacancies in red-emitting CsPb(Br/I)₃ PQDs. This approach nearly triples the photoluminescence quantum yield (PLQY, from 23% to 58%). Systematic structural, morphlogical, binding energy, Fermi level and optical analyses confirm effective defect suppression and enhanced exciton luminescence. The dual-passivated sample QDs:SB3-18@SiO₂ also exhibit excellent environmental stability, retaining 85% of their initial emission after 30 min in air and exhibiting improved UV resistance. By combining the PQDs with a CGSO:Tb³⁺ mechanoluminescent phosphor, a composite film is fabricated with bimodal optical response—color-selective photoluminescence under UV excitation and stress-activated green emission upon scratching. This work presents a robust route to high-performance PQDs and demonstrates their potential for advanced anticounterfeiting and smart optical applications. Full article

Perovskite quantum dots (PQDs) based on CsPbX₃ (X = Cl, Br, I) have attracted extensive attention due to their outstanding optoelectronic properties; however, their practical applications are hindered by poor environmental stability. In this work, a sequential surface-modification strategy is developed to address these limitations. First, CsPbBr₃ PQDs are passivated with (3-aminopropyl) triethoxysilane (APTES), which reduces surface defects and enhances the photoluminescence quantum yield (PLQY) from 38.5% to 74.4%. Subsequently, a dense silica shell is constructed via in situ hydrolysis of tetramethyl orthosilicate (TMOS), further improving the PLQY to 95.6% and significantly boosting environmental stability. Structural and optical characterizations confirm effective defect passivation and suppress non-radiative recombination, with carrier lifetimes extended from 2.5 ns to 36.9 ns. Remarkably, the silica-coated PQDs retain over 50% of their initial emission intensity after 100 min of water immersion, far exceeding the stability of uncoated counterparts. Furthermore, when integrated with a commercial K₂SiF₆: Mn⁴⁺ red phosphor and a blue light-emitting diode (LED) chip, the resulting white LED (WLED) exhibits a wide color gamut covering 104% of the National Television System Committee (NTSC) standard and Commission Internationale de l’Éclairage (CIE) coordinates of (0.323, 0.331), closely matching standard white light. Importantly, only the silica-coated PQDs maintain a stable electrically driven device emission spectrum after water exposure. Full article

The chemical identity of oxygen species plays a decisive role in determining the optical stability of halide perovskite QD films. Here, real-time in situ spectroscopic monitoring, together with steady-state and time-resolved photoluminescence measurements, is utilized to differentiate the effects of molecular oxygen and plasma-activated oxygen species on CsPbBr₃ QD films. The films maintain nearly unchanged emission intensity, spectral profile, and carrier lifetimes when stored in vacuum or exposed to molecular O₂ even under UV illumination, demonstrating that neutral O₂ exhibits minimal reactivity toward the [PbBr₆]⁴⁻ framework. In contrast, oxygen plasma generates highly reactive atomic and ionic oxygen species that induce rapid and spatially heterogeneous photoluminescence quenching. This degradation is attributed to Br⁻ extraction, Br-vacancy formation, and subsequent Pb–O bond generation, which collectively introduce deep trap states and enhance nonradiative recombination. These findings clearly indicate that reactive oxygen species rather than molecular O₂ are the dominant driver of oxygen-induced luminescence degradation, providing mechanistic insight and offering processing guidelines for the reliable integration of perovskite nanomaterials in optoelectronic devices. Full article

In high energy density physics, the demand for precise detection of nanosecond-level fast physical processes is high. Ga:ZnO (GZO), GaN, and other fast scintillators are widely used in pulsed signal detection. However, many of them, especially wide-bandgap materials, still face issues of low luminous intensity and significant self-absorption. Therefore, an enhanced method was proposed to tune the wavelength of materials via coating perovskite quantum dot (QD) films. Three-layer samples based on GZO were primarily investigated and characterized. Radioluminescence (RL) spectra from each face of the samples, as well as their decay times, were obtained. Lower temperatures further enhanced the luminous intensity of the samples. Its overall luminous intensity increased by 2.7 times at 60 K compared to room temperature. The changes in the RL processes caused by perovskite QD and low temperatures were discussed using the light tuning and transporting model. In addition, an experiment under a pico-second electron beam was conducted to verify their pulse response and decay time. Accordingly, the samples were successfully applied in beam state monitoring of nanosecond pulsed proton beams, which indicates that GZO wafer coating with perovskite QD films has broad application prospects in pulsed radiation detection. Full article

Lead halide perovskite quantum dots, also known as perovskite nanocrystals, are considered one of the most promising photovoltaic materials for solar cells due to their outstanding optoelectronic properties and simple preparation techniques. The key factors restricting the photoelectric conversion efficiency of solar cell systems are the separation and transmission performances of charge carriers. Here, femtosecond time-resolved ultrafast spectroscopy was used to measure the interfacial charge transfer dynamics of different sizes of CsPbBr₃ assembled with TiO₂. The effect of perovskite size on the charge transfer is discussed. According to our experimental data analysis, the time constants of the interfacial electron transfer and charge recombination of the assembled systems of CsPbBr₃ and titanium dioxide become larger when the size of the CsPbBr₃ nanocrystals increases. We discuss the physical mechanism by which the size of perovskites affects the rate of charge transfer in detail. We expect that our experimental results provide experimental support for the application of novel quantum dots for solar cell materials. Full article

Coupling organic light-harvesting materials with lead halide perovskite quantum dots (LHP QDs) is an attractive approach that could provide great potential in optoelectronic applications owing to the diversity of organic materials available and the intriguing optical and electronic properties of LHP QDs. Here, we demonstrate energy collection by CsPbI₃ QDs from a near-infrared (NIR) light-harvesting upconversion system. The upconversion system consists of Pd-tetrakis-5,10,15,20-(p-methoxycarbonylphenyl)-tetraanthraporphyrin (PdTAP) as the sensitizer to harvest NIR photons and rubrene as the annihilator to generate upconverted photons via triplet fusion. Steady-state and time-resolved photoluminescence spectra reveal that CsPbI₃ QDs are energized via radiative energy transfer from the singlet excited rubrene with photophysics fidelity of respective components. In addition, a volumetric display demo incorporating CsPbI₃ QDs as light emitters employing triplet fusion upconversion was developed, showing bright luminescent images from CsPbI₃ QDs. These results present the feasibility of integrating organic light-harvesting systems and perovskite QDs, enabling diverse light harvesting and activation of perovskite materials for optoelectronic applications. Full article

Perovskite quantum dots (PQDs), with their excellent optical properties, have become a leading semiconductor material in the field of optoelectronics. However, to date, it has been a challenge to achieve the three-dimensional high-resolution patterning of perovskite quantum dots. In this paper, an in situ femtosecond laser-direct-writing technology was demonstrated for three-dimensional high-resolution patterned CsPbBr₃ PQDs using a two-photon photoresist nanocomposite doped with the CsPbBr₃ perovskite precursor. By adjusting the laser processing parameters, the minimum line width of the PQDs material was confirmed to be 98.6 nm, achieving a sub-100 nm PQDs nanowire for the first time. In addition, the fluorescence intensity of the laser-processed PQDs can be regulated by the laser power. Our findings provide a new technology for fabricating high-resolution display devices based on laser-direct-writing CsPbBr₃ PQDs materials. Full article

The variable bandgap and high absorption coefficient of all-inorganic halide perovskite quantum dots (QDs), particularly CsPbBr₂I make them highly promising for photodetector applications. However, their high defect density and poor stability limit their performance. To overcome these problems, Mn²⁺-doped CsPbBr₂I QDs with varying concentrations were synthesized via the one-pot method in this work. By replacing Pb²⁺ ions, moderate Mn²⁺ doping caused lattice contraction and improved crystallinity. At the same time, Mn²⁺-doping effectively passivated surface defects, reducing the defect density by 33%, and suppressed non-radiative recombination, thereby improving photoluminescence (PL) intensity and carrier mobility. The optimized Mn:CsPbBr₂I QDs-based photodetector exhibited superior performance, with a dark current of 1.19 × 10⁻¹⁰ A, a photocurrent of 1.29 × 10⁻⁵ A, a responsivity (R) of 0.83 A/W, a specific detectivity (D*) of 3.91 × 10¹² Jones, an on/off ratio up to 10⁵, and the response time reduced to less than 10 ms, all outperforming undoped CsPbBr₂I QDs devices. Stability tests demonstrated enhanced durability, retaining 80% of the initial photocurrent after 200 s of cycling (compared to 50% for undoped devices) and stable operation over 20 days. This work offers a workable strategy for rational doping and structural optimization in the construction of high-performance perovskite optoelectronic devices. Full article

Monolayer MoS₂ has been widely researched in high performance phototransistors for its high carrier mobility and strong photoelectric conversion ability. However, some defects in MoS₂, such as vacancies or impurities, provide more possibilities for carrier recombination; thus, restricting the formation of photocurrents and resulting in decreased responsiveness. Herein, all-inorganic CsPbBr₃ perovskite quantum dots (QDs) with high photoelectric conversion efficiency and light absorption coefficients are introduced to enhance the responsivity of a 2D MoS₂ phototransistor. The CsPbBr₃/MoS₂ heterostructure has a type II energy band, and it has a high responsivity of ~1790 A/W and enhanced detectivity of ~2.4 × 10¹¹ Jones. Additionally, the heterostructure CsPbBr₃/MoS₂ enables the synergistic effect mechanism of photoconduction and photogating effects with the gate tunable photo-response, which could also contribute to an improved performance of the MoS₂ phototransistor. This work provides new strategies for performance phototransistors and is expected to play an important role in many fields, such as optical communication, environmental monitoring and biomedical imaging, and promote the development and application of related technologies. Full article

This paper presents an overview of research results on the physical and technological features of crystal formation with an ordered distribution of vacancies. It is noted that the composition and properties of complex chalcogenide phases are not always described by the traditional concepts behind Kroeger’s theory. Model concepts are considered in which the carriers of properties in the crystalline state are not molecules, but an elementary crystalline element with a given arrangement of nodes with atoms and vacancies. It is established that the introduction of the term “quasi-element atom” of the zero group for a vacancy allows us to predict a number of compounds with an ordered distribution of vacancies. Examples of the analysis of peritectic multicomponent compounds and solid solutions based on them are given. Quasi-crystalline concepts are applicable to perovskite materials used in solar cells. It is shown that the photoluminescence of perovskite lead-cesium halides is determined by crystalline structural subunits i.e., the anionic octets. This is the reason for the improvement in the luminescent properties of colloidal quantum CsPbBr₃ dots under radiation exposure conditions. Full article

We conducted experiments utilizing the scattering effect of zinc oxide (ZnO) to enhance the photoluminescence (PL) intensity of cesium lead bromide (CsPbBr₃) perovskite quantum dots (QDs). This study involved investigating the method for creating a CsPbBr₃ and ZnO mixture and determining the optimal mixing ratio. A mixture dispersion of CsPbBr₃ and ZnO, prepared at a 1:0.015 weight ratio through shaking, was fabricated into a film using the spin coating method. The PL intensity of this film showed a relative increase of 20% compared to the original CsPbBr₃ QD film without ZnO. The scattering effect of ZnO was confirmed through ultraviolet-visible (UV-Vis) absorption and transient PL experiments, and a long-delayed exciton lifetime was observed in the optimized mixture dispersion thin film. The morphology of the fabricated film was characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). For the CsPbBr₃-ZnO mixture (1:0.0015) film, crystal domains of approximately 10 nm were observed using TEM. Through AFM analysis, an excellent film roughness of 4.6 nm was observed, further confirming the potential of perovskite QD/ZnO composite films as promising materials for enhanced photoconversion intensity. In future studies, applying this method to other perovskite materials and metal oxides for the optimization of photoconversion composite materials is expected to enable the fabrication of highly efficient perovskite QD/metal oxide composite films. Full article

CsPbIBr₂, with its suitable bandgap, shows great potential as the top cell in tandem solar cells. Nonetheless, its further development is hindered by a high defect density, severe carrier recombination, and poor stability. In this study, CsPbI_1.5Br_1.5 quantum dots were utilized as an additive in the ethyl acetate anti-solvent, while a layer of CsPbBr₃ QDs was introduced between the ETL and the CsPbIBr₂ light-harvester film. The combined effect of these two QDs enhanced the nucleation, crystallization, and growth of CsPbIBr₂ perovskite, yielding high-quality films characterized by an enlarged crystal size, reduced grain boundaries, and smooth surfaces. And a wider absorption range and better energy band alignment were achieved owing to the nano-size effect of QDs. These improvements led to a decreased defect density and the suppression of non-radiative recombination. Additionally, the presence of long-chain organic molecules in the QD solution promoted the formation of a hydrophobic surface, significantly enhancing the long-term stability of CsPbIBr₂ PSCs. Consequently, the devices achieved a PCE of 9.20% and maintained an initial efficiency of 85% after 60 days of storage in air. Thus, this strategy proves to be an effective approach for the preparation of efficient and stable CsPbIBr₂ PSCs. Full article

Radiation possesses inherent physical characteristics, such as penetrability and radionuclide energy, which enable its widespread applicability in fields such as medicine, industry, environment, security, and research. Advancements in scintillator-based radiation detection technology have led to revolutionary changes by ensuring the safe use and precise measurement of radiation. Nevertheless, certain fields require higher scintillation yields to obtain more refined and detailed results. Therefore, in this study, we explored inorganic scintillators coated with perovskite nanomaterials to detect gamma rays with high light yields. By mixing perovskite with a polymer, we improved the intrinsic characteristics of quantum dots, which otherwise failed to maintain their performance over time. On this basis, we investigated the interactions among inorganic scintillators and a mixed material (CsPbBr3 + PMMA) and confirmed an increase in the scintillation yield and measurement trends. Furthermore, optimized scintillation yield measurement experiments facilitated gamma spectroscopy, demonstrating the validity of our approach through the analysis of the peak channel increases in the energy spectra of various gamma sources in relation to the increased scintillation yield. Full article

Encapsulating Cs₄PbBr₆ quantum dots in silicon nano-sheets not only stabilizes the halide perovskite, but also takes advantage of the nano-sheet for a compatible integration with the traditional silicon semiconductor. Here, we report the preparation of un-passivated Cs₄PbBr₆ ellipsoidal nanocrystals and pseudo-spherical quantum dots in silicon nano-sheets and their enhanced photoluminescence (PL). For a sample with low concentrations of quantum dots in silicon nano-sheets, the emission from Cs₄PbBr₆ pseudo-spherical quantum dots is quenched and is dominated with Pb²⁺ ion/silicene emission, which is very stable during the whole measurement period. For a high concentration of Cs₄PbBr₆ ellipsoidal nanocrystals in silicon nano-sheets, we have observed Förster resonance energy transfer with up to 87% efficiency through the oscillation of two PL peaks when UV excitation switches between on and off, using recorded video and PL lifetime measurements. In an area of a non-uniform sample containing both ellipsoidal nanocrystals and pseudo-spherical quantum dots, where Pb²⁺ ion/silicene emissions, broadband emissions from quantum dots, and bandgap edge emissions (515 nm) appear, the 515 nm peak intensity increases five times over 30 min of UV excitation, probably due to a photon recycling effect. This irradiated sample has been stable for one year of ambient storage. Cs₄PbBr₆ quantum dots encapsulated in silicon nano-sheets can lead to applications of halide perovskite light emitting diodes (PeLEDs) and integration with traditional semiconductor materials. Full article