In this paper the modelling of the reflectivity of two quantum well solar cells (QWSC) are theoretically developed and computationally analysed. The new reflectivity model is based on the Modified Single Effective Oscillator model combined with Fresnel's equation. The model takes into consideration the effects of the design parameters including concentration levels, structural properties of the device (well length, etc.), operating temperature and electric field effects. The results generated are for a bare AlGaAs/GaAs cell and the same cell with a ZnS antireflection coating (ARC). Further investigations include a bare SiGe/Si cell and the same cell with a Ta2O5 ARC. The results generated are accurate and match with experimental data for similar cells. The analysis is performed for AM 1.5 spectrum. The model is intended to be an aid to QWSC designers. (C) 2003 Elsevier B.V. All rights reserved.