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We derive the matrix elements of Coulomb interaction between states with different numbers of electrons and holes in a semiconductor nanocrystal within the eight-band k • p theory. These matrix elements are responsible for multiple exciton generation which may contribute to the enhancement of the efficiency of solar cells. Our calculations are performed within the multiband envelope function formalism based on the states resulting from diagonalization of the eight-band k • p Hamiltonian. We study in detail and compare two contributions to the interband Coulomb coupling: the mesoscopic one, which involves only the envelope functions and relies on band mixing, and the microscopic one, which relies on the Bloch parts of the wave functions and is nonzero even between single-band states. We show that these two contributions are of a similar order of magnitude. We also study the statistical distribution of the magnitudes of the interband Coulomb matrix elements and show that the overall coupling to remote states decays according to a power law favorable for the convergence of numerical computations. [ABSTRACT FROM AUTHOR]

The population dynamics of single exciton and biexciton states in a simple model of a spherical semiconductor nanostructure is modeled numerically in the presence of Coulomb coupling between single and two exciton states and a dissipation channel in order to study the transient biexciton population that occurs in an optically excited semiconductor nanocrystal. The results show that the system evolution strongly changes if the dissipation is included. In a certain range of parameters, the growth of the exciton number (multiple exciton generation process) is fast (on picosecond time scale) and the following decay (Auger process) is much slower (hundreds of picoseconds). In some cases, the maximum occupation of the biexciton state increases when dissipation is included. The dynamics of an ensemble of nanostructures with a certain size dispersion is studied by averaging over the energy of the biexciton state which can be different for each single nanostructure. The validity of Markov and secular approximation is also verified. [ABSTRACT FROM AUTHOR]

A correction the article "Interband Coulomb coupling in narrow-gap semiconductor nanocrystals: k • p theory," by Pawel Machnikowski and Maryam Azizi that was published in the 2015 issue is presented.