Modelling the Confined States in Multi Quantum Well Solar Cells

The strain balanced quantum well solar cell (SB-QWSC) provides a novel method of engineering the bandgap of a p-i-n junction to better match the terrestrial solar spectrum. The ability to accurately model the spectral response of a SB-QWSC is vital in optimising cell design. We present a study into two major components of such a model. Firstly, we provide an overview of the model for the confined energy levels within SB-QWSCs and outline the method used to determine a vital parameter for such calculations; the conduction band offset. Secondly, a critical evaluation of the hole in-plane effective masses (required to model the device absorption) is given. A multi-band k.p model is used to calculate the in-plane valence band dispersion and values for the effective masses are extracted from fits to the resulting E-k curves. The results of these investigations are then used to model the spectral response of a typical SB-QWSC. Good agreement is observed between absolute prediction and measured quantum efficiencies