Low-Budget Photoluminescence Imaging

Reducing the prices of characterization systems facilitates their application not only offline, but also inline, improves quality assurance in photovoltaic production and enables the optimization of cell efficiency and yield while reducing the overall costs. We report on a low-budget photoluminescence imaging (PLi) prototype for silicon samples. The prototype is based on light emitting diode illumination to excite excess charge carriers in the sample and an uncooled silicon sensor camera to detect the luminescence radiation. The hardware cost of both components is approximately 90% lower than the laser-based illumination units with optics and cooled silicon or InGaAs sensor based cameras and filters typically used in high-end PLi systems. The prototype is characterized with respect to the illumination intensity, its homogeneity and calibration to implied voltage. An intensity corresponding approximately to "1 sun" illumination is reached. The nonuniformity of the illumination amounts to 57% (according to IEC Standards) in the present setup configuration, but can be taken into account and corrected during image processing in order to produce homogeneously lit PL images. Sample images recorded with the low-budget prototype are compared qualitatively with those of a high-end system, showing decent image quality for the low-budget system.