Modeling the spectral response of the quantum well solar cell

The quantum well solar cell is an alternative to more conventional multiband gap approaches to higher cell efficiency. Preliminary studies have shown that the insertion of a series of quantum wells into the depletion region of a GaAs/AlxGa1−xAs p-i-n solar cell can significantly enhance the cell’s short-circuit current. We present here a model for the spectral response of GaAs and AlxGa1−xAs p-n and p-i-n solar cells, with and without quantum wells, based on a standard solution of the minority-carrier equations. Particular emphasis is placed on modeling the absorption coefficient of the AlxGa1−xAs and of the quantum wells. We find that our model can accurately predict the spectral response of a wide variety of cells: both conventional p-n junctions in GaAs and AlxGa1−xAs, and various geometries of quantum well solar cell in AlxGa1−xAs/GaAs (x∼0.3). We discuss the strengths and weaknesses of the model and its underlying assumptions, and conclude by using the model to design p-i-n quantum well solar cells with higher short-circuit current outputs.