What caused the secondary peak in our photoluminescence experiment?

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SUMMARY

The discussion centers on a photoluminescence experiment involving CdS quantum dot structures in toluene, excited by a 325 nm 50 mW continuous wave Kimmon UV laser. The results show a secondary peak at approximately 400 nm in the higher concentration sample, while the peak wavelength remains consistent across both samples. The secondary peak is hypothesized to be related to size dispersion differences between quantum dots QD1 and QD2. Further investigation is needed to clarify the origin of this secondary peak.

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Septim
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Greetings everyone,

We have performed a photoluminescence experiment and plotted the resultant spectra for two samples of different concentration after correcting for the response of the CCD camera and got the results that is attached to this post. My question is that in the sample with higher concentration the peak is at the same wavelength; however, we have an additional secondary peak at around 400 nm. We were not able to explain this and I would be happy to know why it was observed. Both of the samples were CdS quantum dot structures in toluen and the samples were excited with a 325 nm 50 mW continuous wave operating Kimmon UV laser.

Thanks in advance
 

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It may be QD1 and QD2 with different size dispersions.
 

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