qds

Quantum dots (QDs) are nanoscale semiconductor particles whose electronic and optical properties arise from quantum confinement. Typically 2–10 nanometers in diameter, their band gap and, therefore, their emission wavelength can be tuned by size, shape, and composition. As a result, QDs show size-dependent photoluminescence with narrow, symmetric emission spectra and high color purity.

Common material systems include II–VI semiconductors such as CdSe, CdS, ZnS; InP; and more recently lead halide perovskite QDs CsPbX3 and other perovskites. Core/shell architectures (for example CdSe core with a ZnS or CdS shell) address surface traps and improve quantum yield and stability. Type-I and Type-II heterostructures control where electrons and holes reside, influencing radiative lifetimes and charge separation.

Synthesis Colloidal synthesis in solution using hot-injection methods enables control over size distribution and crystallinity. Surface ligands stabilize QDs in solvents; shell growth is used to passivate surface defects and enhance stability. There are cadmium-containing and cadmium-free options; Cd-free InP or perovskites are pursued for environmental safety.

Properties include high photoluminescence quantum yields, broad absorption with narrow emission, tunable by size/composition; issues such as photobleaching, blinking (intermittent emission). Strategies include core/shell architectures, thick shells, and surface chemistry improvements.

Applications span displays (QLEDs), solid-state lighting, solar cells, photodetectors, biological imaging, and sensors, with potential in quantum information processing.

Challenges include toxicity and long-term stability, especially for lead-based perovskites, moisture sensitivity, reproducibility, scale-up, and broader environmental impact.