Methods (200, 300), apparatuses and systems (100) for determining minority carrier diffusion lengths in a semi-conductor structure (130), which may be a solar cell or a unprocessed or partially processed silicon sample, are disclosed. The luminescence (140) may comprise photoluminescence, electroluminescence, or both. Luminescence (140) is excited (212) in the structure (130), and the intensities of short- and long-wavelength luminescence (140) are measured (214). Luminescence intensities may be captured from either side of the sample using a single photodetector, a FPA, a CCD array (150), or a mapping tool. The luminescence (140) excited in the structure (130) may be filtered (160) at short and long cutoff wavelengths. Diffusion lengths of the structure (130) are generated (216) using a predefined theoretical relationship. The generating step (216) may comprise calculating (316) intensity ratios from luminescence intensities and converting (320) the intensity ratios into diffusion lengths using the predefined theoretical relationship.