Exact Solution for Excess Electrons in Quantum

– We derive excess carrier populations in quantum wells, embedded in the intrinsic region of p-i-n solar cells. In the process of the analysis, we (a) solve for photo-generated carriers in quantum wells and (b) determine explicit dependence on incident solar wavelength. We include in the computations the existence of optical gaps near 1eV or wavelengths in the near infrared, so that our complete device design covers both visible and IR spectra simultaneously: a clear advantage over bulk and nitride-base solar currently studied solar cells. In the process of derivations, we include the effect of recombination losses via cumulative Auger recombination coefficients cn on photo-excited carriers in intrinsic quantum wells nph, as found in the middle region of p-i-n solar cells, leading to an explicit new result of the form: nph ~ cn.We find the total carrier concentration to be the sum of photo-excited and background carriers, namely, ntotal = nph + no. Our approach is general and can be applied to different semiconducting layers, while as a concrete application, we select lattice-matched germanium and gallium arsenide layers forming quantum wells. Excess carrier concentrations of the order of 10 per unit volume are predicted for thin GaAs-Ge quantum wells, under steady solar photon incidence, while the background dark carrier concentration is near 10 carriers per unit volume. Key-Words: quantum wells, solar cells, solar spectrum, Auger recombination, material growth, quantum photovoltaics