Exciton Broadening in Quantum Well Solar Cells

The incorporation of quantum wells into GaAs solar cells extends the absorption edge towards lower energy, which can lead to higher efficiencies. At concentrator current levels the main carrier loss mechanism is radiative recombination from the quantum wells. We have previously reported on a high-bias effect in the e1-hh1 exciton electroluminescence (EL) in strain-balanced quantum well solar cells. In this paper, we define a metric for this effect by fitting a Lorentzian line shape to the exciton absorption as calculated from EL spectra using a generalised Planck approach, examine the effect in light of the full width half maximum, height, and area of the Lorentzian, and consider possible sources of the effect.