We report application of phase shifting interferometric measurements to study of the spatially resolved quantum efficiency (QE) of the semiconductor solar-cells. In our method solar-cell is illuminated by two sets of mutually spatially orthogonal fringe patterns of known frequency, and varying phase (shifted phase). We report theoretical results obtained using simple analytical model describing properties of small spot size defects, and preliminary experimental results validating this method. The new method and new apparatus can be also used for studies of spectrally resolved QE.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.