Intermediate-band solar cells: Influence of band formation on dynamical processes in InAs/GaAs quantum dot arrays

We present a theoretical model for design and analysis of semiconductor quantum dot (QD) array-based intermediate-band solar cell (IBSC). The plane-wave method with periodic boundary conditions is used in expansion of the k.p Hamiltonian for calculation of the electronic and optical structures of InAs/GaAs QD array. Taking into account realistic QD shape, QD periodicity in the array, as well as effects such as band mixing between states in the conduction and valence band, strain and piezoelectric field, the model reveals the origin of the intermediate-band formation inside forbidden energy gap of the barrier material. Having established the interrelation between QD periodicity and the electronic structure across the QD array Brillouin zone, conditions are identified for the appearance of pure zero density-of-states regions, that separate intermediate band from the rest of the conduction band. For one realistic QD array we have estimated all important absorption coefficients in IBSC, and most important, radiative and nonradiative scattering times. Under radiative-limit approximation we have estimated efficiency of such IBSC to be 39%.