Photoluminescence (PL) is the most common technique for characterizing materials used for photovoltaics and light-emitting diodes. The material is initially excited by photons from a laser source and then subsequently emits photons at a different energy which is characteristic of the studied material. The lifetime of the PL is related to the lifetime of the photoexcited carriers and depends on the quality of the material. The typical information which can be extracted from the PL data is the band gap energy of the material, the presence of defects in the lattice and possible quantum confinement effects in nanometer-sized crystals.
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