Abstract Highly efficient green and red perovskite quantum dots (PeQDs) light‐emitting diodes (PeQDLEDs) have been achieved. However, blue PeQDLEDs, especially those with the relatively short wavelengths (<470 nm) meeting National Television System Committee blue standard, have struggled to match the high efficiency and stability of their red and green counterparts. The main critical problems are the low photoluminescence quantum yield (PLQY) and poor stability of PeQDs, as well as the unfavorable device structure. Herein, a strategy of codoping Mn 2+ and Ni 2+ in CsPb(Br 1.8 Cl 1.2 ) is developed to improve the PLQY and thermal stability of PeQDs due to the defect passivation and enhanced formation energy. Meanwhile, the valence band position of PeQDs is elevated to reduce the hole injection barrier benefitting from the synergetic codoping strategy. As a result, the PeQDLEDs based on codoped PeQDs exhibit the maximum external quantum efficiency (EQE) of 3.31% with the emission peak located at 469 nm, and lifetime exceeding 8 min. The work provides a new avenue to achieve efficient and stable pure blue PeQDLEDs.
It is well-known that carbonation is characterized by a rapid initial rate followed by an abrupt transition to a very slow reaction rate. The slow period is believed to be controlled by the diffusion of reacting species throughout the product layer of CaCO3. The thickness of the carbonate layer formed on the free surfaces of CaO is a critical parameter to mark the end of the fast reaction period. This study addresses the question of how temperature affects the reaction process. For example, when the carbonation reaction enters the product layer diffusion-controlled stage at a low temperature such as 500 °C, how does an increase to 600 °C affect the conversion as a function of time and what changes occur in the CaCO3 product layer morphology? This work discusses the interesting finding that the fast reaction stage is recovered again when the temperature is increased. To understand and explain this phenomenon, it is necessary to investigate the mechanism of the temperature effect on the carbonation reaction. Many phenomena are not well explained by the theory of a critical product layer thickness, which is now used almost exclusively to explain the "maximum" conversion during carbonation reaction cycles. Therefore, we provide a new insight into this issue from a nanoscale point of view by combining thermogravimetric analysis (TGA) with the trapping mode (TM) of an atomic force microscope (AFM) to explain the mechanism of the reaction temperature's effect on the reaction rate and solid conversion characteristics.
Abstract We present a liquid‐crystal display (LCD) backlight made of nanoplatelets (NPLs) for the first time. Owing to the narrow emission linewidth of NPLs (8‐12 nm) and quantum dots (QDs), the spectrum exhibits a wide color gamut display with a 139.9% color gamut of National Television System Committee (NTSC) 1953 standard and 104.5% Rec.2020 (ITU‐R Recommendation BT.2020), realizing a truly ultrawide color gamut LCD display.
Quantum dots (QDs) have attracted much attention as one of the most promising candidates for next-generation display materials. However, stability is still a big challenge for QDs. Herein, we encapsulated QDs in a thermoplastic polypropylene (PP) matrix by thermal processing technology to prepare a stabler color conversion film for the first time. Thermal processing technology expands the packaging materials of QDs from traditional soluble polymers to thermoplastic polymers such as PP with easy processing and a low cost. We showed that the QDs in the PP film exhibited longer-lasting stability than the traditional PMMA film. After 216 h of blue light accelerated aging test, the QDs maintained more than 90% of the initial performance in the PP film but dropped to less than 25% in the PMMA film. Moreover, the reasons for the improved stability have been further discussed. It was found that the PP-H film not only possessed better barriers to moisture and oxygen, but the absence of ester groups also led to a milder environment around the QDs. The results show that ester groups have stronger electronegativity and easily cause the ligands on the surface of QDs to fall off, which lead to performance degradation.
Slag tapping cyclone furnace is suitable and promising for the utilization of low-ash-melting-point coals without worrying about the fouling and slagging problems, but its high NO x emission has limited its application. In this study, the temperature profiles, species concentration distributions, and slag tapping behavior of the cyclone barrel were explored on a self-built 100 kW cyclone furnace system. A reasonable slag capture ratio of 0.70 can be achieved for the cyclone barrel even under air-staged conditions. The coincidence of high temperature and high O2 concentration in the annular near-wall area of the cyclone barrel can lead to a large amount of NO x formation, while a NO x reduction area with high CO concentration is formed in the central and lower zones of the cyclone barrel due to strong swirling effect. The NO x emission of cyclone staged combustion is lower than that of laminar drop-tube staged combustion in either air-staged or nonstaged cases, which could be attributed to the swirling effect. The NO x reduction area can be expanded by decreasing the cyclone stoichiometric ratio (SR) or reducing the primary air rate (PAR). Compared with the limit effects on the reduction of NO x emission by overall-SR, NO x formation can be greatly dropped by 56% when the cyclone-SR decreases from 1.1 to 0.7. The swirling intensity in cyclone barrel increases from 1.23 to 12.81 as PAR reduces from 0.4 to 0.2, which results in a reduction of NO x formation at the outlet of the cyclone barrel by half. Besides, the O2 concentration in the annular near-wall region can be remarkably reduced by the decentralized secondary air supply, resulting in a 23% reduction in NO x formation in the cyclone barrel.
High-alkali Zhundong coal presents significant challenges for power generation, due to its propensity for fouling and slagging. This study investigates a retrofit of a 300 MW tangentially fired boiler with the integration of a slag-tap chamber to improve combustion performance. Computational fluid dynamics (CFD) simulations are employed to examine the influence of this modification on combustion dynamics and the effects of Zhundong coal blending ratios on heat and mass transfer. The results demonstrate that the retrofit facilitates stable airflow recirculation, optimizing combustion efficiency with a peak temperature of 2080 K in the combustion chamber. The flue gas temperature decreases to approximately 1650 K upon exit, which can be attributed to the slag catcher cooling. The integration of the liquid slagging chamber significantly mitigates slag formation, while enhancing oxygen and CO2 distribution throughout the furnace. As the blending ratio of Zhundong coal increases, oxygen concentrations rise in the bottom burner region, indicating improved air–fuel mixing. With a 30% Zhundong coal ratio, the combustion chamber temperature increases by 3%, and flow velocity in the upper and middle furnace sections decreases by 15%, leading to enhanced combustion intensity. This retrofit demonstrates substantial improvements in combustion stability, slagging control, and the efficient utilization of high-alkali coal.
Zero-dimension (0-D) lead halide perovskite nanocrystals (NCs) have attracted a sight of interest in the field of optoelectronic devices due to their outstanding properties, such as high photoluminescence quantum yield (PLQY) and size- and composition-controlled tunable emission wavelengths. However, the toxicity of lead (Pb) element in the lead perovskite NCs is the bottleneck for the commercial application of perovskite NCs. Herein, we report a facile ligand-assisted synthesis to achieve lead-free Cs 3 Cu 2 Cl 5 NCs with a high PLQY of ∼70% and good stability against environmental oxygen/moisture as a promising down-conversion material. It has good merits of high PLQY and large Stokes shift (∼300 nm) originated from the effect of Jahn–Teller distortion and self-trapped excitons (STEs). Furthermore, the Cs 3 Cu 2 Cl 5 NCs embedded composite films (NCCFs) were utilized to enhance the ultraviolet (UV) response of silicon (Si) photodetectors. External quantum efficiency (EQE) measurements show that the UV response can be greatly improved from 3.3 to 19.9% @ 295 nm based on NCCFs combined with Si photodiodes. Our work offers an effective approach to develop highly efficient and stable lead-free Cs 3 Cu 2 Cl 5 NCs for the application in the solar-blind UV photodetector.
Optical performance in terms of light efficiency, color crosstalk and ambient contrast ratio were analyzed for blue GaN-based micro-light emitting diodes (micro-LEDs) combined with red/green quantum dots (QDs)-polymethyl methacrylate (PMMA) films. The thickness and mass ratio of QDs films are two critical factors in affecting the performance of micro-LEDs. Firstly, the precise optical modeling of QDs-PMMA films is established based on the double integrating sphere (DIS) testing system and inverse adding doubling algorithm (IADA) theory. Red and green QDs-PMMA films are composed of ZnCdSe/ZnS QDs and green ZnCdSeS/ZnS QDs, respectively. The fundamental optical parameters of QDs-PMMA films, including scattering, absorption and anisotropy coefficients, are obtained successfully. Secondly, based on these optical parameters, the Monte Carlo ray tracing method is applied to analyze the effect of a QDs-PMMA film’s thickness and mass ratio on the optical performance of micro-LEDs. Results reveal that the light efficiency first increases and then decreases with the increase of a QDs film’s thickness or mass ratio, owing to the scattering characteristics of QDs. Different from the variation tendencies of light efficiency, the crosstalk between adjacent pixels increases as the QDs-PMMA film’s thickness or mass ratio increases, and the ambient contrast ratio is kept stable when the thickness increases. The mass ratio variation of QDs film can change the optical performance of micro-LEDs more effectively than thickness, which demonstrates that mass ratio is a more important factor affecting the optical performance of micro-LEDs.
Severe environmental pollution is caused by the massive discharge of complex industrial wastewater. The photocatalytic technology has been proved as an effective way to solve the problem, while an efficient photocatalyst is the most critical factor. Herein, a new photocatalyst MIL-68(Ga)_NH2 was obtained by hydrothermal synthesis and were characterized by PXRD, FTIR, 1H NMR, and TGA systematically. The result demonstrates that MIL-68(Ga)_NH2 crystallized in orthorhombic system and Cmcm space group with the unit cell parameters: a = 36.699 Å, b = 21.223 Å, c = 6.75 Å, V = 5257.6 Å3, which sheds light on the maintenance of the crystal structure of the prototype material after amino modification. The conversion of Cr(VI) and binary pollutant Cr(VI)/RhB in wastewater under visible light stimulation was characterized by the UV-vis DRS. Complementary experimental results indicate that MIL-68(Ga)_NH2 exhibits remarkable photocatalytic activity for Cr(VI) and the degradation rate reaches as high as 98.5% when pH = 2 and ethanol as hole-trapping agent under visible light irradiation with good reusability and stability. Owing to the synergistic effect between Cr(VI) and RhB in the binary pollutant system, MIL-68(Ga)_NH2 exhibits excellent catalytic activity for both the pollutants, the degradation efficiency of Cr(VI) and RhB was up to 95.7% and 94.6% under visible light irradiation for 120 min, respectively. The possible removal mechanism of Cr(VI)/RhB based on MIL-68(Ga)_NH2 was explored. In addition, Ga-based MOF was applied in the field of photocatalytic treatment of wastewater for the first time, which broadened the application of MOF materials in the field of photocatalysis.
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