Impacts of ambipolar carrier escape on current-voltage characteristics in a type-I quantum-well solar cell

We study the current-voltage characteristics of a GaAs/AlGaAs quantum well solar cell (QWSC) at different temperatures. The photocurrent of the QWSC decreases from the short-circuit level with increasing forward bias, resulting in a low fill factor of the cell. The photocurrent reduction is attributed to the carrier confinement in the QW, which is investigated in detail by changing the temperature and excitation wavelength. We observe two reduction steps in the photocurrent at low temperature, and find that the different hole and electron tunneling rates are responsible for the two reductions.