Wafer-scale epitaxial modulation of quantum dot density

Controlling Quantum-Confined Stark Effect in Coupled II-VI Quantum Dots by Interface Engineering

Electric-field tuning of excitonic states in confined systems via the quantum-confined Stark effect (QCSE) provides a flexible way for electro-optic modulation with great efficiency. In epitaxial and colloidal quantum dots (QDs), the interdot coupling allows additional degrees of freedom for optical switches. Here QCSE is explored in artificial molecules formed by two coupled QDs of main group II-VI elements. Compared with a single QD, the QCSE is remarkably enhanced in QD molecules and highly tunable by the interdot coupling strength as well as by homo- and hetero-dimerization of QDs. In addition, the strong coupling between QDs can retard charge separation under an external electric field and even bring the electron and hole states from two QDs into a resonance, thereby boosting the fluorescence emission in QD molecules. These mechanistic understandings provide vital guidelines for fine manipulation of electron, spin, and exciton in coupled QDs and their assemblies for tunable optoelectronics, photonics, and quantum information applications.

Shutter-Synchronized Molecular Beam Epitaxy for Wafer-Scale Homogeneous GaAs and Telecom Wavelength Quantum Emitter Growth

Quantum dot (QD)-based single-photon emitter devices today are based on self-assembled random position nucleated QDs emitting at random wavelengths. Deterministic QD growth in position and emitter wavelength would be highly appreciated for industry-scale high-yield device manufacturing from wafers. Local droplet etching during molecular beam epitaxy is an all in situ method that allows excellent density control and predetermines the nucleation site of quantum dots. This method can produce strain-free GaAs QDs with excellent photonic and spin properties. Here, we focus on the emitter wavelength homogeneity. By wafer rotation-synchronized shutter opening time and adapted growth parameters, we grow QDs with a narrow peak emission wavelength homogeneity with no more than 1.2 nm shifts on a 45 mm diameter area and a narrow inhomogeneous ensemble broadening of only 2 nm at 4 K. The emission wavelength of these strain-free GaAs QDs is <800 nm, attractive for quantum optics experiments and quantum memory applications. We can use a similar random local droplet nucleation, nanohole drilling, and now, InAs infilling to produce QDs emitting in the telecommunication optical fiber transparency window around 1.3 µm, the so-called O-band. For this approach, we demonstrate good wavelength homogeneity and excellent density homogeneity beyond the possibilities of standard Stranski-Krastanov self-assembly. We discuss our methodology, structural and optical properties, and limitations set by our current setup capabilities.

New Strategy for Microbial Corrosion Protection: Photocatalytic Antimicrobial Quantum Dots

Microbial corrosion has significant implications for the economy, environment, and human safety worldwide. Photocatalytic antibacterial technology, owing to its advantages in environmental protection, broad-spectrum, and efficient sterilization, presents a compelling alternative to traditional antibacterial strategies for microbial corrosion protection. In recent years, photocatalytic quantum dot materials have garnered considerable attention in this field due to their unique quantum effects. This article provides a brief overview of the quantum effects associated with quantum dot materials, reviews the classification and preparation methods of these photocatalytic quantum dots, and elucidates their inhibitory effects and mechanisms against microbial corrosion. Finally, this article summarizes unresolved issues and prospects for the future development of quantum dots in the realm of microbial corrosion protection.

Recent Progress of Quantum Dots Light-Emitting Diodes: Materials, Device Structures, and Display Applications

Colloidal quantum dots (QDs), as a class of 0D semiconductor materials, have generated widespread interest due to their adjustable band gap, exceptional color purity, near-unity quantum yield, and solution-processability. With decades of dedicated research, the potential applications of quantum dots have garnered significant recognition in both the academic and industrial communities. Furthermore, the related quantum dot light-emitting diodes (QLEDs) stand out as one of the most promising contenders for the next-generation display technologies. Although QD-based color conversion films are applied to improve the color gamut of existing display technologies, the broader application of QLED devices remains in its nascent stages, facing many challenges on the path to commercialization. This review encapsulates the historical discovery and subsequent research advancements in QD materials and their synthesis methods. Additionally, the working mechanisms and architectural design of QLED prototype devices are discussed. Furthermore, the review surveys the latest advancements of QLED devices within the display industry. The narrative concludes with an examination of the challenges and perspectives of QLED technology in the foreseeable future.

External-quantum-efficiency enhancement in quantum-dot solar cells with a Fabry-Perot light-trapping structure

In this work, we have experimentally investigated the impact of light trapping on the performance of InAs/GaAs quantum dot (QD) solar cells. To increase the amount of absorbed near-infrared photons, we fabricated a thin-film QD solar cell with a backside mirror where the positions of the QD layers were matched with the intensity peaks of one of the Fabry-Perot (FP) resonances in this structure to enable enhanced QD absorption near 1192 nm. We demonstrate that the external quantum efficiency at a given FP resonance wavelength of such an InAs/GaAs-based QD solar cell can be increased by an order of magnitude over solar cells without FP resonance by optimally positioning the QD layers.