The first version of a solar cell simulator specifically designed for the analysis of multijunction solar cells is presented. The simulation program solves the Poisson and continuity equations by using a procedure optimized for multilayer structures. It includes the radiative interband, Shockley-Read-Hall and Auger recombination mechanisms, and computes the generation function of electron-hole pairs from the optical parameters of the cell materials. The dependence of these optical parameters with the photon energy has been included, taking into account the doping level and its effect on bandgap narrowing. The simulator is applied to the analysis of a dualjunction GaInP/GaAs solar cell, obtaining results comparable to experimental data reported by different authors. More advanced versions of the simulator are in progress, with the aim of obtaining a tool useful for optimal design of multijunction solar cells.

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An equation that includes the effects of non-parabolicity on the conduction band of a semiconductor is applied to different nanosystems. This allows us to obtain analytical expressions in systems with simple geometries and reveals significant differences in relation to those obtained in parabolic cases. For quantum wells, we propose an empirical energy-wave vector dispersion relationship that can be used in electron transport simulation. In the case of quantum dots, by choosing suitable parameter values, the results obtained using the non-parabolic model are adjusted to those produced by tight binding. The introduction of non-parabolicity corrections is shown to greatly modify the energy spectrum. To illustrate this fact, we use as an example a system useful in a quantum dot laser.

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