Advanced Optical Materials最新文献

The instability of halide perovskite nanocrystals (PNCs) upon exposure to water is a longstanding problem that has limited the full potential of these materials. Here, this issue is assessed from the point of view of supramolecular chemistry. This approach triggers the self-assembly of low molecular weight gelators (LMWGs) at the point of the synthesis of PNCs for their simultaneous incorporation into the supramolecular gel formed by those. Thus, a library of peptide-based molecules is designed which can replace oleyl amine in the synthesis of CsPbBr₃ PNCs via the Hot Injection procedure. In situ gelation is achieved during the synthesis process and the impact of self-assembly on the water durability of the PNCs is studied. The photocatalytic activity of the most stable PNCs is established by measuring the ability of these materials to degrade Rhodamine B in water. In addition, the self-assembled peptide network is efficient to prevent lead leaching in water substantially eliminating the lead contamination by the catalyst. Moreover, completely degraded perovskite material can self-heal to a certain extent within the matrix to revert to its primitive perovskite phase. Altogether, these results open a new way for the use of LMWGs to improve the (re)usability of halide perovskite materials.

Van der Waals materials and devices incorporating them exhibit highly thickness-dependent properties. The small lateral dimensions of mechanically exfoliated 2D-layered flakes, however, remarkably complicate their precise thickness determination. Quantitative analysis of reflectance measurements using optical microspectroscopy is proven to be as precise as spectroscopic ellipsometry while providing an easily adaptable and non-destructive method for thickness determination. The use of magnifying objective lenses allows obtaining the reflectance within a measurement spot of only a few microns in diameter. When the dimensions of exfoliated flakes are even smaller, however, the acquired reflectance is a superposition of those of the material of interest and the subjacent materials. To overcome this limitation, a facile approach to reduce the resolvable structure size by combining the evaluation of the reflectance measurement via transfer matrix method with spatial information extracted from optical micrographs is introduced. The efficacy when characterizing micrometer-sized flakes is exemplarily demonstrated for thickness determination of highly oriented pyrolytic graphite and a thin film of silicon dioxide. It is shown that a maximum error of less than 10% is achieved even when the flake only covers 20% of the measurement spot.

MXene quantum dots (MQDs), in contrast to their precursor metallic MXenes, display photoluminescence (PL), and with the advantages of non-toxicity, ease of synthesis, and low cost, they are promising quantum materials for optoelectronic and photonic devices. However, as-synthesized MQDs suffer from low quantum yield (QY) and a large Stokes shift, limiting efficient UV emission, and are subject to Auger recombination, that is, a severe decline of QY and PL lifetime with increasing exciton density. Here, fluorine-free Ti₂N MQDs are synthesized using a single-step solvothermal process, which emits UV light of a peak wavelength of 370 nm with a greatly improved QY of 17.4%, and superior resistance to Auger recombination. Band structure calculations and X-ray photoelectron spectroscopy measurements indicate that Ti₂N MQDs synthesized by using the solvothermal process are free of fluorine which is normally prevalent on the surfaces of MQDs prepared by an ordinary hydrothermal process. The results shed light on the mechanism of improving QY and mitigating Auger recombination of MQDs helping their practical applications, especially for photonic devices in the UV range.

Doping lanthanide ions in double perovskites (DPs) offers a promising approach to tailor optical and optoelectronic properties for versatile applications. However, achieving efficient and thermal stable DPs remains a significant challenge. In this paper, a series of Cs₂KInCl₆:Yb³⁺,Er³⁺ DPs with a negative thermal quenching behavior and high sensitivity are fabricated. The intrinsic luminescence properties of Cs₂KInCl₆ are studied with a broad intrinsic self-trapped excitons (STEs) emission peak at 500 nm, which can be enhanced by doping Er³⁺ ions accompanied with greater distortion of the [InCl₆]³⁻ octahedrons as well as multiple characteristic emission modes of Er³⁺ under ultraviolet and near-infrared excitation. Notably, the addition of sensitizer Yb³⁺ ions leads to the enhanced up-conversion emission of Er³⁺ (up-conversion quantum yield up to 1.66%), anti-thermal quenching performance brought by the phonon-assisted energy transfer up-conversion process, as well as high sensitivity and reproducibility based on fluorescence intensity ratio technology. This work provides an effective strategy to enhance the STEs emission of DPs and achieve efficient optical temperature sensors through lanthanide ions doping.

Lead halide perovskite nanocrystals (PNCs) combine properties required by high-quality light sources like high brightness, color purity, defects tolerance, and tunable emission wavelength. Notably, their nanoscale size enables integration or fabrication into micro/nano light-emitting devices, which have significant market demand. However, the stability of PNCs remains an open issue for their industrialization. Chemically stable and transparent amorphous silica (SiO₂), an ideal cladding for vulnerable optical materials, is widely utilized to expand the applications of PNCs, resulting in many composites. Nevertheless, current composites remain far from achieving a sufficiently stable high-quality luminescent unit, and the specific challenges in PNCs-SiO₂ integration have not been clearly outlined. To provide inspiration for this field, iodine-containing PNCs are used as a representative example to deliver a comprehensive review of PNCs-SiO₂ development. First, the performance advantages, prospects, and stability challenges of PNCs are analyzed, with a focus on typical cesium lead iodine nanocrystals. Next, the benefits of SiO₂ encapsulation are highlighted and the design, synthesis, and performance improvement of current iodine-containing PNCs-SiO₂ composites are systematically summarized. Finally, optimism about the potential of single-particle encapsulation technology for PNCs is expressed and the challenges and future directions in this field are outlined.

III-V semiconductors, known for their optoelectronic properties and versatile engineering capabilities, play a crucial role in the fabrication of Micro light-emitting diodes (Micro-LEDs). Recent advances in research underscore that the optoelectronic performance of Micro-LEDs can be significantly enhanced using various strategies, such as passivation and distributed Bragg reflectors (DBRs), the incorporation of metamaterials and plasmonics, and the integration of 2D materials. By implementing these diverse integration strategies, Micro-LEDs based on III-V semiconductors have demonstrated remarkably high External Quantum Efficiency (EQE) spanning orders of magnitude across the spectrum, from deep-ultraviolet (DUV) to the long-wavelength infrared (LWIR) regions. In this review, the main III-V semiconductors used in Micro-LEDs are discussed. Additionally, an overview of the fabrication processes and integration techniques relevant to Micro-LED-based technologies is provided. Furthermore, the factors that influence the figure of merit in a wide range of Micro-LEDs based on III-V semiconductors, taking into account quantum efficiency, emission wavelength, and electrical injection, are examined. Finally, the discussion highlights several applications of Micro-LEDs, provides a summary, and outlines future directions for the development of Micro-LEDs based on III-V semiconductors.

The development of stable and deformation-free crystal structures of perovskites and their derivatives are crucial for electroluminescent devices. In this article, a novel transparent manganese-based perovskite derivative K₄MnBr_1.33Cl_4.67 is synthesized with mixed halogens. For the unique octahedral crystal structure, the Jahn-Teller distortion, typically present in such structures, is completely suppressed, resulting in high environmental stability of the luminescence spectrum. In transparent flexible devices, the peak current density, average external quantum efficiency on each side and maximum brightness is 45 mA cm⁻², 4.9%, and 2800 cd m⁻², respectively. The best half-life of the LED reaches 10 h with a starting luminance of 100 cd m⁻². As the first lead-free transparent flexible perovskite derivative LED, it features an outstanding transparency of 76% and excellent flexibility with a luminescence intensity maintenance of 90% after 2000 bending cycles. This work shows that lead-free manganese perovskite derivatives can provide a promising way to fabricate stable and high-performance LEDs.

In this study, the investigation of a Cs₂AgBiBr₆ single crystal (SC) / CsPbBr₃ nanocrystals (NCs) film double perovskite/perovskite type-II novel heterojunction tailored for superior X-ray detection applications is presented. One of the main benefits of utilizing such a heterojunction is its built-in electric potential, which improves charge transport and reduces the dark current in the devices. By casting CsPbBr₃ NCs onto polished Cs₂AgBiBr₆ SC, the Cs₂AgBiBr₆/CsPbBr₃ double perovskite/ perovskite heterojunction is fabricated. The heterojunction X-ray detector exhibits reduced dark current and increased photocurrent compared to the pristine SC device. This enhancement of photocurrent can be attributed to efficient carrier generation and separation facilitated by appropriate band bending at the type-II heterojunction interface. The heterojunction device shows an X-ray sensitivity of 6 µCGy⁻¹ cm⁻² at 0 V of applied bias, owing to the built-in potential across the heterojunction. Remarkably, at a −50 V bias, the sensitivity of the heterojunction device reached 857.8 µCGy⁻¹ cm⁻², with a limit of detection of 312 nGy s⁻¹. Density functional theory (DFT) calculations provided further insights, revealing electron transfer from CsPbBr₃ to Cs₂AgBiBr₆, thereby enhancing the X-ray sensitivity of the heterojunction device. These findings underscore the potential of Cs₂AgBiBr₆/CsPbBr₃ heterojunctions for X-ray detection and optoelectronic applications.

Organic solar cells (OSCs) are suitable candidates for next-generation renewable energy sources due to their low cost of production and flexibility. Their power conversion efficiency has improved significantly to about 20% in both single- and multi-junction devices due to the tremendous work in optimizing the synthesis of novel active-layer materials while improving device fabrication. Despite a few reports predicting a 20-year lifetime for OSC devices, their stability currently lags behind their commercialization. This Review discusses the issues that impair OSC stability and how to mitigate them. While emphasizing the importance of the International Summit on Organic Photovoltaic Stability (ISOS) protocols, an overview of recent advancements in OSC power conversion efficiency (PCE) and lifetime is provided. Finally, fundamental challenges to developing high-performance and stable OSCs are discussed along with general recommendations for improving the stability of OSCs.

The charge-transfer (CT) complexes with significant electron delocalization demonstrate abundant appealing physicochemical features and unique orbital hybridization, creating great promise as artificial light-harvesting antennas for advanced optoelectronics, such as high-performance organic room-temperature phosphorescence (RTP). Herein, originally, a localized CT complex is proposed in organic microcrystals for exceptional orange-emissive RTP with photoluminescence peaks at 575 and 625 nm based on the light-harvesting antennas of CT states in organic microcrystals with donor doping. The localized CT state antennas can capture more singlet excitons, and transition them into triplet excitons, efficiently promoting intersystem crossing (ISC). Owing to the dense packing structure and strong CT interaction, the generation and stabilization of triplet excitons under ambient conditions are facilitated, imparting effective RTP with a lasting afterglow of up to 3 s. The controlled intensity ratio of fluorescence and phosphorescence is successfully achieved via finely adjusting the donor doping ratio, presenting a tunable CIE evolution from (0.42, 0.30) to (0.25, 0.12). The potential applications of these light-harvesting microcrystals in information encryption and flexographic printing are illustrated.