Highly stable Na: CsPb(Br,I)3@Al2O3 nanocomposites prepared by a pre-protection strategy

Multi-Functional Ethylene-vinyl Acetate Copolymer Flexible Composite Film Embedded with Indium Acetate-Passivated Perovskite Quantum Dots

In recent years, all-inorganic cesium lead halide perovskite quantum dots have emerged as promising candidates for various optoelectronic applications, including sensors, light-emitting diodes, and solar cells, owing to their exceptional photoelectric properties. However, their commercial utilization has been limited by stability issues. In this study, we addressed this challenge by passivating the surface defects of CsPbBr3 quantum dots using indium acetate, a metal-organic compound. The resulting CsPbBr3 quantum dots exhibited not only high photoluminescence intensity, but also a remarkably narrow half-peak width of 19 nm. Furthermore, by embedding the CsPbBr3 quantum dots in ethylene-vinyl acetate, we achieved stretchability and significantly enhanced stability while preserving the original luminous intensity. The resulting composite film demonstrated the potential to improve the power conversion efficiency of crystalline silicon solar cells and enabled the creation of excellent white light-emitting diodes with coordinates of (0.33, 0.31). This co-passivation strategy, involving surface passivation and polymer packaging, provides a new idea for the practical application of CsPbBr3 quantum dots.

Sr2+doped CsPbBrI2perovskite nanocrystals coated with ZrO2for applications as white LEDs

Perovskite nanocrystals (NCs) feature adjustable bandgap, wide absorption range, and great color purity for robust perovskite optoelectronic applications. Nevertheless, the absence of lasting stability under continues energization, is still a major hurdle to the widespread use of NCs in commercial applications. In particular, the reactivity of red-emitting perovskites to environmental surroundings is more sensitive than that of their green counterparts. Here, we present a simple synthesis of ultrathin ZrO₂coated, Sr²⁺doped CsPbBrI₂NCs. Introducing divalent Sr²⁺may significantly eliminate Pb° surface traps, whereas ZrO₂encapsulation greatly improves environmental stability. The photoluminescence quantum yield of the Sr²⁺-doped CsPbBrI₂/ZrO₂NCs was increased from 50.2% to 87.2% as a direct consequence of the efficient elimination of Pb° surface defects. Moreover, the thickness of the ZrO₂thin coating gives remarkable heat resistance and improved water stability. Combining CsPbSr_0.3BrI₂/ZrO₂NCs in a white light emitting diode (LED) with an excellent optical efficiency (100.08 lm W^-1), high and a broad gamut 141% (NTSC) standard. This work offers a potential method to suppress Pb° traps by doping with Sr²⁺and improves the performance of perovskite NCs by ultrathin coating structured ZrO₂, consequently enabling their applicability in commercial optical displays.

Monolithic Multicolor Emissions of InGaN-Based Hybrid Light-Emitting Diodes Using CsPbBr3 Green Quantum Dots

To address the increasing demand for multicolor light-emitting diodes (LEDs), a monolithic multicolor LED with a simple process and high reliability is desirable. In this study, organic-inorganic hybrid LEDs with violet and green wavelengths were fabricated by depositing CsPbBr₃ perovskite green quantum dots (QDs) as the light-converting material on InGaN-based violet LEDs. As the injection current was increased, the total electroluminescence (EL) intensities of the hybrid LEDs increased, whereas the light-converted green emission efficiency of the CsPbBr₃ QDs decreased. The maximum green-to-violet EL spectral intensity ratio of the hybrid LEDs with CsPbBr₃ QDs was achieved with the injection current of <10 mA. Moreover, the EL spectral ratio of the green-to-violet emission decreased at an injection current of 100 mA. The light-conversion intensity of the CsPbBr₃ QDs decreased linearly as the junction temperature of the hybrid LEDs was increased with increasing injection current, similar to the temperature-dependent photoluminescence degradation of CsPbBr₃ QDs. In addition, the junction temperature of the hybrid LED was minimized by pulse injection to suppress the thermal degradation of QDs and increase the light conversion efficiency to green emission. Therefore, the overall emission spectrum color coordinates of the hybrid LEDs exhibited a red shift from violet to blue in the low-current region and a blue shift toward violet as the green emission of the QDs was decreased above 10 mA.

Rubidium ions doping to improve the photoluminescence properties of Mn doped CsPbCl3perovskite quantum dots

All-inorganic cesium lead halide CsPbX₃(X = Cl, Br, I) perovskite quantum dots (PQDs) have shown promising potential in current Mini/Micro-LED display applications due to their excellent photoluminescence performance. However, lead ions in PQDs are easily to leak owing to the unstable structure of PQDs, which hinders their commercial applications. Herein, we adopt Rb⁺ions co-doping strategy to regulate the doping characteristics of Mn²⁺ions in CsPbCl₃PQDs. The synthesized CsPbCl₃:(Rb⁺, Mn²⁺) PQDs possess enhanced photoluminescence quantum yield of 71.1% due to the reduction of intrinsic defect states and Mn-Mn or Mn-traps in co-doped PQDs. Moreover, the white light emission of CsPb(Cl/Br)₃:(Rb⁺, Mn²⁺) PQDs is achieved by anion exchange reaction and the constructed WLED exhibits the CIE coordinate of (0.33, 0.29) and the correlated color temperature of 5497 K. Benefiting from the substitution strategy, these doped CsPbX₃PQDs can be widely used as fluorescence conversion materials for the construction of Mini/Micro-LED.

Highly stable lanthanide-doped CsPbI3 perovskite nanocrystals with near-unity quantum yield for efficient red light-emitting diodes

CsPbI₃ perovskite nanocrystals (NCs) are gaining popularity as promising photoactive materials for optoelectronic devices. However, their poor phase stability has caused substantial limitations in their practical application. Herein, the small-sized rare earth La cation is strategically introduced to fundamentally improve the NC phase stability against the environment, heat, and UV radiation by the partial substitution of Pb ions to suppress structural distortion and increase the formation energy. The strong interaction between La and I of the octahedra has been demonstrated to enable the effective suppression of the trap states, which promotes strengthened radiative recombination for a near-unity photoluminescence quantum yield (PLQY) of 99.3%. High energy bands have also been found for the La-doped NCs to narrow down the energy barrier for efficient hole injection. The superior optoelectronic properties of La-doped NCs promote great improvements in the perovskite light-emitting diode (PeLED) performances with a 5-fold improvement in external quantum efficiency (EQE) from 1.19 to 6.01% and 2-fold longer lifetime from 1451 to 2956 s. This work provides an effective method for small-sized metal ion-doped CsPbI₃ NCs to realize high emission efficiency and phase stabilization for efficient PeLEDs.

Highly Orientated Perovskite Quantum Dot Solids for Efficient Solar Cells

Perovskite quantum dots (PQDs) have emerged as competitive optoelectronic materials for photovoltaic applications due to their ideal bandgap energy, high defect tolerance, and solution processability. However, the highly dynamic surface and imperfect cubic structure of PQDs generally result in unfavorable charge-carrier transport within the PQD solids and serious nonradiative recombination. Herein, a highly orientated PQD solid is demonstrated using precursor engineering accompanied by a chemical stripping treatment (CST). A combination of systematic experimental studies and theoretical calculations is conducted to fundamentally understand the resurfacing of PQDs using the CST approach. The results reveal that the highly ordered PQDs can result in a high orientation of PQD solids, significantly promoting charge-carrier transport within the PQD solids. Meanwhile, the ideal cubic-structured PQD with an iodine-rich surface dramatically decreases surface trap states, thereby substantially diminishing trap-assisted nonradiative recombination. Consequently, the inorganic PQD solar cell delivers a power conversion efficiency of up to 16.25%. This work provides a feasible avenue to construct highly orientated PQD solids with improved photophysical properties for high-performance optoelectronic devices.

Enhancing oxygen/moisture resistance of quantum dots by short-chain, densely cross-linked silica glass network

Quantum dots (QDs) are facing significant photoluminescence degradation in moisture environment. In QDs-silicone composites, the poor water resistance of silicone matrix makes it easy for water and oxygen molecules to erode QDs. To tackle this issue, we proposed a new QDs protection strategy by introducing short-chain silica precursors onto the QDs' surface, so that a dense silica passivation layer could be formed onto the QDs nanoparticles. Sol-gel method based on 3-aminopropyl triethoxysilane (APTES), 3-mercaptopropyl trimethoxysilane (MPTMS), and 3-mercaptopropyl triethoxysilane (MPTES) were adopted to prepare the uniform and crack-free QDs-silica glass (QD-glass). Because of the crosslinking of short-chain precursors, the formed silica glass possesses 38.6% smaller pore width and 68.6% lower pore volume than silicone, indicating its denser cross-linked network surrounding QDs. After 360 h water immersion, the QDs-glass demonstrated a 6% enhancement in red-light peak intensity, and maintained a stable full width at half maximum (FWHM) and peak wavelength, proving its excellent water-resistant ability. However, the conventional QDs-silicone composites not only showed a decrease of 75.3% in red-light peak intensity, but also a broadened FWHM and a redshifted peak wavelength after water immersion. QDs-glass also showed superior photostability after 132 h exposure to blue light. Red-light peak intensity of QDs-glass remained 87.3% of the initial while that of QDs-silicone decreased to 19.8%. And the intensity of QDs-glass dropped to 62.3% of that under 20 °C after thermal treatment of 160 °C. Besides, under increasing driving currents, the light conversion efficiency drop of QDs-glass is only one fifth that of QDs-silicone. Based on the QDs-glass, the white light-emitting diodes was achieved with a high luminous efficiency of 126.5 lm W^-1and a high color rendering index of 95.4. Thus, the newly proposed QD-glass has great significance in guaranteeing the working reliability of QDs-converted devices against moisture and high-power environment.

Strong violet emission from ultra-stable strontium-doped CsPbCl3 superlattices

Among the lead halide perovskites, the photoluminescence quantum yields (PLQYs) of perovskite quantum dots (PQDs) in the violet region are the very lowest. This is an obstacle to the optical applications across the entire visible area based on perovskite materials. Herein, we report a novel strontium (Sr)-substitution along with chlorine passivation strategy to enhance the PLQYs of CsPbCl₃ PQDs. We surprisingly found that when the molar ratio of Sr²⁺/Pb²⁺ = 0.1/0.9, CsSr_0.1Pb_0.9Cl₃ PQDs exhibit strong single-color violet emission, which is attributed to the effective passivation of chlorine defects. We further found spontaneous self-assembly of PQDs into highly emissive PSCs from the precursor in a highly concentrated solution. Moreover, by dilution of these PSCs, a few small PQD aggregates can be regained, which is similar to the PQDs formed at lower concentrations. Benefiting from the superior collective properties of individual PQDs, these highly fluorescent CsSr_0.1Pb_0.9Cl₃ PSCs can maintain good stability even when directly immersed in water or exposed to illumination.

Tuning optical properties of CsPbBr3by mixing Nd3+trivalent lanthanide halide cations for blue light emitting devices

In recent years, significant progress has been made in the red and green perovskite quantum dots (PQDs) based light-emitting devices. However, a scarcity of blue-emitting devices that are extremely efficient precludes their research and development for optoelectronic applications. Taking advantage of tunable bandgaps of PQDs over the entire visible spectrum, herein we tune optical properties of CSPbBr₃by mixing Nd³⁺trivalent lanthanide halide cations for blue light-emitting devices. The CsPbBr₃PQDs doped with Nd³⁺trivalent lanthanide halide cations emitted strong photoemission from green into the blue region. By adjusting their doping concentration, a tunable wavelength from (515 nm) to (450 nm) was achieved with FWHM from (37.83 nm) to (16.6 nm). We simultaneously observed PL linewidth broadening thermal quenching of PL and the blue shift of the optical bandgap from temperature-dependent PL studies. The Nd³⁺cations into CsPbBr₃PQDs more efficiently reduced non-radiative recombination. As a result of the efficient removal of defects from PQDs, the photoluminescence quantum yield (PLQY) has been significantly increased to 91% in the blue-emitting region. Significantly, Nd³⁺PQDs exhibit excellent long-term stability against the external environment, including water, temperature, and ultraviolet light irradiation. Moreover, we successfully transformed Nd³⁺doped PQDs into highly fluorescent nanocomposites. Incorporating these findings, we fabricate and test a stable blue light-emitting LED with EL emission at (462 nm), (475 nm), and successfully produce white light emission from Nd³⁺doped nanocomposites with a CIE at (0.32, 0.34), respectively. The findings imply that low-cost Nd³⁺doped perovskites may be attractive as light converters in LCDs with a broad color gamut.

Exploiting a Multiphase Pure Formamidinium Lead Perovskite for Efficient Green-Light-Emitting Diodes

Formamidinium (FA)-based perovskites have demonstrated excellent advances in optoelectronics recently, but in terms of perovskite compounds, the optimal condition of their composition optimization remains controversial. Herein, we boosted the performance of perovskite light-emitting diodes (PeLEDs) in both efficiency and stability through composition and phase engineering. The low-dimensional FA₂PbBr₄ particles emerged and mixed with the FAPbBr₃ composites when the FABr content is excessive. By regulating the phase composition in multiphase FAPbBr₃ perovskites, the maximum external quantum efficiency (EQE_max) of optimal PeLEDs (5.14%) is 2.7-fold higher than that of pure FAPbBr₃-based PeLEDs (1.90%), and device stability is improved. Further optimizing the film quality and emission efficiency with Rb⁺ ions, the EQE_max of PeLEDs can be increased to 6.01%, with a half-lifetime of about 185 s under the high current density. This strategy of phase composition optimization in FA-based perovskites provides an effective way to process high-efficiency and stable PeLEDs.

Trioctylphosphine-Assisted Pre-protection Low-Temperature Solvothermal Synthesis of Highly Stable CsPbBr3/TiO2 Nanocomposites

Lead halide perovskite quantum dots (PQDs) are reported as a promising branch of perovskites, which have recently emerged as a field in luminescent materials research. However, before the practical applications of PQDs can be realized, the problem of poor stability has not yet been solved. Herein, we propose a trioctylphosphine (TOP)-assisted pre-protection low-temperature solvothermal synthesis of highly stable CsPbBr₃/TiO₂ nanocomposites. Due to the protection of branched ligands and the lower temperature of shell formation, these TOP-modified CsPbBr₃ PQDs are successfully incorporated into a TiO₂ monolith without a loss of fluorescence intensity. Because the excellent nature of both parent materials is preserved in CsPbBr₃/TiO₂ nanocomposites, it is found that the as-prepared CsPbBr₃/TiO₂ nanocomposites not only display excellent photocatalytic activity but also yield improved PL stability, enabling us to build highly stable white light-emitting diodes and to photodegrade rhodamine B.

Highly Luminescent and Stable CsPbI3 Perovskite Nanocrystals with Sodium Dodecyl Sulfate Ligand Passivation for Red-Light-Emitting Diodes

CsPbI₃ perovskite nanocrystals (NCs) have recently emerged as promising materials for optoelectronic devices because of their superior properties. However, the poor stability of the CsPbI₃ NCs induced by easy ligand desorption represents a key issue limiting their practical applications. Herein, we report stable and highly luminescent black-phase CsPbI₃ NCs passivated by novel ligands of sodium dodecyl sulfate (SDS). Theoretical calculation results reveal a stronger adsorption energy of SDS molecules at the CsPbI₃ surface than that of commonly used oleic acid. As a result, the defect formation caused by the ligand loss during the purification process is greatly suppressed. The optimized SDS-CsPbI₃ NCs exhibit significantly reduced surface defects, much enhanced stability, and superior photoluminescence efficiency. The red perovskite light-emitting diodes based on the SDS-CsPbI₃ NCs demonstrate an external quantum efficiency of 8.4%, which shows a 4-fold improvement compared to the devices based on the oleic acid-modified CsPbI₃ NCs.

A versatile approach for shape-controlled synthesis of ultrathin perovskite nanostructures

We demonstrate that ultrathin CsPbBr₃ nanostructures can be obtained by a simple mixing of precursor–ligand complexes under ambient conditions.

Stable near white light emission in CsPbCl3 perovskite quantum dots by incorporating Al3+/Mn2+ ions

All inorganic cesium lead halides (CsPbX3, X = Cl, Br, I) are promising materials and have been developed in recent years for various optoelectronic devices and applications because of their excellent optoelectronic properties. Regardless of their excellent characteristics their stability is still uncertain and it is challenging task to obtain stable emission in CsPbX3 perovskite quantum dots (PQDs), hence limiting their practical optoelectronic application. In this context, several approaches have been used like an-ion exchange, ion doping, and core–shell structure to enhance PQDs stability. Herein, we synthesized dual ion co-doped Al3+/Mn2+ CsPbCl3 PQDs for stable light emitting diodes through traditional hot injection method for the first time. By adjusting molar concentration of Al3+/Mn2+ CsPbCl3, co-doped PQDs were successfully prepared. The co-doped PQDs exhibit tunable emission, covering a wide range under UV excitation. Moreover, these high luminescent co-doped PQDs were used to fabricate WLEDs, displaying stable near white light emission with the chromaticity coordination at (0.35, 0.28). Some new evidence has emerged, although some aspects of Mn2+ and Al3+ doping are considered to be consistent with previous conclusions. This viewpoint incorporates all of these details and focuses on the path of transition metal ion doping to perovskite nanostructures and offers an overview for possible potential studies.

Pressure-Driven Transformation of CsPbBrI2 Nanoparticles into Stable Nanosheets in Solution through Self-Assembly

Very recently, two-dimensional (2D) perovskite nanosheets (PNSs), taking the advantages of perovskite as well as the 2D structure properties, have received an enormous level of interest throughout the scientific community. In spite of this incredible success in perovskite nanocrystals (NCs), self-assembly of many nanostructures in metal halide perovskites has not yet been realized, and producing highly efficient red-emitting PNSs remains challenging. In this Letter, we show that by using CsPbBrI₂ perovskite nanoparticles (NPs) as a building block, PNSs can emerge spontaneously under high ambient pressure via template-free self-assembly without additional complicated operation. It is found that the formation of PNSs is ascribed to the high pressure that provides the driving force for the alignment of NPs in solution. Because of the disappearance of the grain boundaries between the adjacent NPs and increased crystallinity, these PNSs self-assembled from NPs exhibit enhanced properties compared to the initial NPs, including higher PL intensity and remarkable chemical stability toward light and water.