Correcting the inherent distortion in luminescence images of silicon solar cells

Abstract

Luminescence imaging of Silicon solar cells is typically performed with a silicon CCD, which is a poor absorber of silicon luminescence (900-1300 nm). This leads to a phenomenon referred to as photon smearing in the CCD, where a photon incident on one pixel may be absorbed in another. This makes the image blurry and quantitative analysis of this data inaccurate. Also resolution, contrast, and sharpness of the image are reduced at features such as grain boundaries, and sample edges. An already established method of recovering the original luminescence signal incident on the CCD is to deconvolve a Point Spread Function (PSF) with the resultant image. This paper focuses on a novel method for determining the PSF from a measurement of the Edge Spread Function, which greatly increases the Signal to Noise ratio over methods where the PSF is measured directly. The determined PSF and its application to luminescence images, is compared and contrasted with previously published PSF determination methods.