Suppressing the Auger recombination process in quantum dotsA Quantum Dot (QD) is a nanometer-sized s

Suppressing the Auger recombination process in quantum dots

A Quantum Dot (QD) is a nanometer-sized semiconductor nanocrystal that has unique optical properties such as the ability to emit light in the range of optical frequencies depending on its size. QDs have already been applied to practical optoelectronic applications including light-emitting displays, solar cells, photodetectors, and lasers.

In general, QDs have two distinct energy bands in which electrons can exist. They are the so-called “valence band” where electrons are fully occupied and the “conduction band” where electrons are empty, respectively. The gap between these two bands is called the “band gap,” where electrons cannot exist. Upon photoexcitation by light with higher energy than the band gap, electrons within the valence band can be excited and jump into the conduction band. A vacancy formed in the valence band after this process is called a “hole,” which is defined as a carrier having a positive charge.

A hole usually pairs with an electron in the conduction band and forms a quasi-particle called an “exciton” that is bound via Coulomb interaction. After formation, the exciton can recombine spontaneously and emit light with the same energy as the band gap. The most important parameter in this process is the “transition dipole moment,” which is an electric dipole moment associated with the transition between the two states. Typically, the larger this quantity, the greater the recombinationrate.

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