Near-Infrared Nanophosphors Based on CuInSe2 Quantum Dots with Near-Unity Photoluminescence Quantum Yield for Micro-LEDs Applications

Combining Quantum Dots and Photochromic Molecular Switches: Next-Generation Light-Responsive Materials

Quantum dots (QDs), with the unique merits of narrow and tunable photoluminescence (PL) wavelength, high PL quantum yield, have gained significant interest in fields such as display, solar energy conversion, bioimaging, and encrypted quantum communication. On the other hand, photochromic molecular switches (PMS) can undergo reversible interconversion between (at least) two distinct states at the molecular scale upon light irradiation. When combining QDs and PMS, the resulting hybrid systems exhibit synergistic functionalities and light responsiveness, enabling precise and reversible modulation over PL intensity/color, energy/electron transfer, and motion with high temporal and spatial resolution in a non-invasive manner. This perspective explores the recent advancements in the combination method, light-responsive mechanism, and functions of QD-PMS hybrids. The applications of QD-PMS hybrids are also highlighted as light-responsive materials in bioimaging, information processing, sensing, optoelectrical devices, and discuss future challenges, opportunities, and directions for enhancing performance and exploring applications in next-generation light-responsive materials and smart optoelectronic devices.

Microwave-assisted synthesis of highly photoluminescent core/shell CuInZnSe/ZnS quantum dots as photovoltaic absorbers

Water-dispersible core/shell CuInZnSe/ZnS (CIZSe/ZnS) quantum dots (QDs) were efficiently synthesized under microwave irradiation using N-acetylcysteine (NAC) and sodium citrate as capping agents. The photoluminescence (PL) emission of CIZSe/ZnS QDs can be tuned from 593 to 733 nm with varying the Zn : Cu molar ratio in the CIZSe core. CIZSe/ZnS QDs prepared with a Zn : Cu ratio of 0.5 exhibit the highest PL quantum yield (54%) and the longest PL lifetime (515 ns) originating from the recombination of donor-acceptor pairs. The potential of CIZSe/ZnS QDs as photoabsorbers in QD-sensitized solar cells was also evaluated. An adequate type-II band alignment is observed between TiO2 and CIZSe/ZnS QDs, indicating that photogenerated electrons in CIZSe/ZnS QDs could efficiently be injected into TiO2.

Photo-Induced Synthesis of Ytterbium and Manganese-Doped CsPbCl3 Nanocrystals for Visible to Near-Infrared Photoluminescence with Negative Thermal Quenching

Rare-earth-doped all-inorganic perovskite applications for near-infrared (NIR) emission are crucial for the construction of the next generation of intelligent lighting sources. However, the preparation of rare-earth-doped all-inorganic perovskite is complex, and difficult to control, and the issue of thermal quenching poses significant challenges to its practical application. Here, in order to address these issues, a convenient photo-induced synthesis method for CsPbCl3:Mn/Yb nanocrystals (NCs) is proposed by decomposing carbon tetrachloride with 365 nm light to provide chloride ions and regulate the formation of perovskite at room temperature. The negative thermal quenching in the NIR emission is achieved through the energy transfer between Mn and Yb. The emission intensity of Yb enhances 3.2 times when the temperature rises to ≈427 K. Furthermore, with the help of the orange emission from the Mn2+ ions and the NIR emission from the Yb3+ ions, visible to NIR light emitting diode (LED) devices are constructed and applied in orange light illumination and night vision imaging. This study enriches the preparation methods and chemical research on perovskite doping, which may open up new opportunities for the widespread application of perovskite-based materials or device engineering.

Growth of Ultrathick CuInS2 Shells for Supersized Core/Shell Nanoparticles

The growth of ultrathick shells on quantum dots (QDs) has been demonstrated to provide new aspects of nanoparticles (NPs). Spherical dot-shaped CuInSe2 QDs were produced with the advantage of shell growth due to their homogeneous surface. The superthickness (∼45 nm) of CuInS2 was deposited on the CuInSe2 dots to form supersized CuInSe2/CuInS2 core/shell nanostructures with a tetrakaidecahedron shape to ∼100 nm. This quasi-epitaxial growth mechanism was extended to form supersized ZnSe/CuInS2 and CuInS2/CuInS2 core/shell nanostructures, thereby providing an efficient method for supersized nanoparticles based on shell growth. The formation of supersized nanoparticles (20-100 nm) may induce new chemistry and physics for nanomaterials, supplying new aspects in fundamental research and the commercial industry.

Optical Applications of CuInSe2 Colloidal Quantum Dots

The distinctive chemical, physical, electrical, and optical properties of semiconductor quantum dots (QDs) make them a highly fascinating nanomaterial that has been extensively studied. The CuInSe2 (CIS) QDs demonstrates great potential as a nontoxic alternative to CdSe and PbSe QDs for realizing high-performance solution-processed semiconductor devices. The CIS QDs show strong light absorption and bright emission across the visible and infrared spectrum and have been designed to exhibit optical gain. The special characteristics of these properties are of great significance in the fields of solar energy conversion, display, and electronic devices. Here, we present a comprehensive overview of the potential applications of colloidal CIS QDs in various fields, with a particular focus on solar energy conversion (such as QD solar cells, QD-sensitized solar cells, and QD luminescence solar concentrators), solar-to-hydrogen production (such as photocatalytic and photoelectrochemical H2 production), and QD electronics (such as QD transistors, QD light-emitting diodes, and QD photodetectors). Furthermore, we offer our insights into the current challenges and future opportunities associated with CIS QDs for further research.

Long-Wavelength Afterglow Emission with Nearly 100% Efficiency through Space-Confined Energy Transfer in Organic-Carbon Dot Hybrid

Long-wavelength afterglow emitters are crucial for optoelectronics and information security; however, it remains a challenge in achieving high luminescence efficiency due to the lack of effective modulation in electronic coupling and nonradiative transitions of singlet/triplet excitons. Here, we demonstrate an organic-carbon-dot (CD) hybrid system that operates via a space-confined energy transfer strategy to obtain bright afterglow emission centered at 600 nm with near-unity luminescence efficiency. Photophysical characterization and theoretical calculation confirm efficient luminescence can be assigned to the synergistic effect of intermolecular energy transfer from triplet excitons of CDs to singlets of subluminophores and the intense restraint in nonradiative decay losses of singlet/triplet-state excitons via rationally space-confined rigidification and amination modification. By utilizing precursor engineering, yellow and near-infrared afterglow centered at 575 and 680 nm with luminescence efficiencies of 94.4% and 45.9% has been obtained. Lastly, these highly emissive powders enable superior performance in lighting and information security.

Crystal Field-Engineered Cr3+-Doped Gd3(MgxGa5-2xGex)O12 Phosphors for Near-Infrared LEDs and X-ray Imaging Applications

Inorganic materials doped with chromium (Cr) ions generate remarkable and adjustable broadband near-infrared (NIR) light, offering promising applications in the fields of imaging and night vision technology. However, achieving high efficiency and thermal stability in these broadband NIR phosphors poses a significant challenge for their practical application. Here, we employ crystal field engineering to modulate the NIR characteristics of Cr3+-doped Gd3Ga5O12 (GGG). The Gd3MgxGa5-2xGexO12 (GMGG):7.5% Cr3+ (x = 0, 0.05, 0.15, 0.20, and 0.40) phosphors with NIR emission are developed through the cosubstitution of Mg2+ and Ge4+ for Ga3+ sites. This cosubstitution strategy also effectively reduces the crystal field strength around Cr3+ ions, which results in a significant enhancement of the photoluminescence (PL) full width at half-maximum (fwhm) from 97 to 165 nm, alongside a red shift in the PL peak and an enhancement of the PL intensity up to 2.3 times. Notably, the thermal stability of the PL behaviors is also improved. The developed phosphors demonstrate significant potential in biological tissue penetration and night vision, as well as an exceptional scintillation performance for NIR scintillator imaging. This research paves a new perspective on the development of high-performance NIR technology in light-emitting diodes (LEDs) and X-ray imaging applications.

Rigid CuInS2/ZnS Core/Shell Quantum Dots for High Performance Infrared Light-Emitting Diodes

CuInS2 (CIS) quantum dots (QDs) represent an important class of colloidal materials with broad application potential, owing to their low toxicity and unique optical properties. Although coating with a ZnS shell has been identified as a crucial method to enhance optical performance, the occurrence of cation exchange has historically resulted in the unintended formation of Cu-In-Zn-S alloyed QDs, causing detrimental blueshifts in both absorption and photoluminescence (PL) spectral profiles. In this study, we present a facile one-pot synthetic strategy aimed at impeding the cation exchange process and promoting ZnS shell growth on CIS core QDs. The suppression of both electron-phonon interaction and Auger recombination by the rigid ZnS shell results in CIS/ZnS core/shell QDs that exhibit a wide near-infrared (NIR) emission coverage and a remarkable PL quantum yield of 92.1%. This effect boosts the fabrication of high-performance, QD-based NIR light-emitting diodes with the best stability of such materials so far.