Digital micromirror device application for inline characterization of solar cells by tomographic light beam-induced current imaging

Abstract

Light Beam-Induced Current (LBIC) imaging is a well-known characterization technique for solar cells, which allows to detect regions of low crystal quality. In this paper a fast, robust and reliable LBIC system is proposed by the use of digital micromirror device (DMD). The LBIC technique is usually performed by point-by-point mechanical sample scanning under a laser spot or by laser scanning, which leads to a measurement time of at least several minutes. In this proposed system with DMD, a new technique is introduced, in which a solar cell is scanned from different angles by a light-line instead of a light-spot. The obtained photocurrent data from these scans are used to reconstruct an LBIC image by using tomography principles. This leads to a lower number of measurements compared to any point scan method. This method helps in reducing measurement time and makes LBIC a fast characterization tool capable for inline investigations. Light-line scans over the cell from different angles are realized by a digital micromirror device (DMD) and its parallel interface controller. The DMD provides a fast solution for line-scanning the cell at speed up to 4 kHz, leading to a measure time of a few tens of seconds for a 256x256 pixel image. Since there are no moving parts involved in this setup, it is a robust and compact system, which will be ideal for the field environment and inline characterization.