what is quantum confinement

Quantum confinement is a phenomenon that occurs when the diameter of a material is of the same magnitude as the de Broglie wavelength of the electron wave function. When materials are this small, their electronic and optical properties deviate substantially from those of bulk materials. Specifically, the effect describes the phenomenon resulting from electrons and electron holes being squeezed into a dimension that approaches a critical quantum measurement, called the exciton Bohr radius. In current application, a quantum dot such as a small sphere confines in three dimensions, a quantum wire confines in two dimensions, and a quantum well confines only in one dimension. These are also known as zero-, one- and two-dimensional potential wells, respectively. The confinement of electronic particles in nanocrystals produces unique optical and electronic properties that have the potential to enhance the power conversion efficiency of solar cells for photovoltaic. The reduction in dimensionality produced by confining electrons (or holes) to a thin semiconductor layer leads to a dramatic change in their behavior. Within a quantum wire, the electron is confined across two directions, rather than just the one in a quantum well, and so the degrees of freedom are reduced to one. In a quantum dot, the electron is confined in all three dimensions, thus reducing the degrees of freedom to zero.