In this paper, we investigate non-single exponential photoluminescence decays in various disordered condensed-matter systems. For such materials, two formulas for the average lifetime of system’s excited state are commonly used in the analysis of experimental data. In many cases, the choice of formula is arbitrary and lacks a clear physical justification. For this reason, our main goal is to show that the choice of correct mathematical formula should be based on the interpretation of measured photoluminescence decay curve. It is shown that depending on the investigated system, after appropriate normalization, photoluminescence decay curve can represent either a survival probability function or a probability density function of lifetime and for this reason two different formulas for the average lifetime are required. It is also shown that, depending on luminescence quantum yield, some information on the probability density function of lifetime can be lost in the process of measurement, which results in underestimated values of average lifetime. Finally, we provide an interpretation of total decay rate distributions which are frequently obtained by phenomenological modeling of non-single exponential photoluminescence decays.

In this work, silicon-rich silicon oxide films containing terbium were prepared by means of plasma enhanced chemical vapor deposition. The influence of hydrogen passivation on defects-mediated non-radiative recombination of excited Tb 3þ ions was investigated by photoluminescence, photoluminescence excitation, and photoluminescence decay measurements. Passivation was found to have no effect on shape and spectral position of the excitation spectra. In contrast, a gradual increase in photoluminescence intensity and photoluminescence decay time was observed upon passivation for the main 5 D 4-7 F 5 transition of Tb 3þ ions. This observation was attributed to passivation of non-radiative recombination defects centers with hydrogen. It was found that the number of emitted photons increases upon passivation as a result of two effects: (1) longer Tb 3þ lifetime in the 5 D 4 excited state and (2) optical activation of new Tb 3þ emitters. The obtained results were discussed and compared with other experimental reports. V

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In this work, silicon nitride films containing terbium were deposited by reactive magnetron co-sputtering in a nitrogen enriched plasma and subjected to rapid thermal annealing treatments. The influence of annealing temperature on the emission and absorption properties of these films was investigated by photoluminescence, photoluminescence decay and photoluminescence excitation measurements. An increase in the photoluminescence intensity and photoluminescence decay time was observed upon annealing for the main 5 D 4 -7 F 5 transition of Tb 3+ ions. This observation was attributed to decrease of the non-radiative recombination and increase of the number of excited Tb 3+ ions upon annealing. Moreover, high temperature annealing was found to shift the spectral position of absorption bands observed in the photoluminescence excitation spectra. In general, these excitation spectra were shown to have a rather complicated structure and were decomposed into three Gaussian bands. It was suggested that two of these excitation bands might be due to indirect excitation of Tb 3+ ions via defects and the third excitation band could be due to direct 4f-5d transition.