Separation of local bulk and surface recombination in crystalline silicon from luminescence reabsorption

Spontaneous photoemission of crystalline silicon provides information on excess charge carrier density and thereby on electronic properties such as charge carrier recombination lifetime and series resistance. This paper is dedicated to separating bulk recombination from surface recombination in silicon solar cells and wafers by exploiting reabsorption of spontaneously emitted photons. The approach is based on a comparison between luminescence images acquired with different optical short pass filters and a comprehensive mathematical model. An algorithm to separate both front and back surface recombination velocities and minority carrier diffusion length from photoluminescence (PL) images on silicon wafers is introduced. This algorithm can likewise be used to simultaneously determine back surface recombination velocity and minority carrier diffusion length in the base of a standard crystalline silicon solar cell from electroluminescence (EL) images. The proposed method is successfully tested experimentally. Copyright © 2009 John Wiley & Sons, Ltd. Luminescence images of silicon solar cells and wafers reveal local electronic properties such as minority carrier diffusion lengths (L) and surface recombination velocities (S) in a combined manner. The separation of these recombination properties becomes increasingly important as solar cell efficiencies steadily improve. In this paper, reabsorption of luminescence is exploited by applying different optical short pass filters in order to separate local bulk recombination from local surface recombination in both silicon solar cells and wafers (image).