Optical absorption coefficient calculations of GaSb/GaAs quantum dots for intermediate band solar cell applications

Absorption coefficients of GaSb/GaAs quantum dots (QDs) are calculated by the 8-band strain-dependent k· p method and Fermi's golden rule. A more realistic but simple approach to model the QD ensemble with wetting layer is described. Effects of the QD size and density, and the GaAs spacer thickness for multi-stacked QDs on absorption characteristics are studied. Absorption spectra of the single QD, single layer of QDs, and multi-stacked QDs are presented and discussed. Interband absorption is found to be more intense than intraband absorption. The calculated absorption spectra are brought into the drift-diffusion model coupled with rate equations to determine the current density-voltage curves of the GaSb/GaAs QD solar cells, which are compared with measured data in literature for validation. The models proposed in this work are capable of predicting the short-circuit current density and open-circuit voltage of real devices, and would have the potential to investigate the impact of doping and position of the QD layers, which is necessary for intermediate band solar cell analysis and design.