dear colleague

the photoluminescence peak of a semiconductor is centered on the corresponding gap Eg which depends of the statistical size average then they are strongly correlated

regards

Thanks sir...

Dear Abhishek,

There are so many reports that the PL emission strongly depends on the particle size. The reason may be as more atoms are located at the particle surface when the particle size is reduced.

The Configuration coordinate diagram of the bulk and nanocrystals may explain this effect. As the particle size changes from bulk to nano, the transfer mechanism of excited electrons also changes.

Thanks sir, I'll try to co-relate it with the Configuration coordinate diagram.

Dear Rupesh Talewar,

I Agree with you. The PL emission strongly depends on the particle size. But the emission intensity increases or decreases with the particle size. Could you explain about configuration coordinate diagram with any one of metal oxide. I am new to this concept.

Abhishek King When a semiconductor or a dielectric material is excited above the bandgap energy and as a result of relaxation, luminescence is observed is called photoluminescence. As a result of relaxation, if only photons are emitted, the bandgap will be a "direct" bandgap, while, if in addition to photons, phonons are also emitted, the bandgap will be an "indirect" bandgap. Since, the phonons emission is due to the defects, impurities, and dopants between CB and VB. When only photons are emitted, the relaxation is called radiative, while, when only phonons are emitted, the relaxation is called nonradiative. We can only find the bandgap energy from PL data in the case of radiative relaxation (direct bandgap). In nonradiative relaxation, when an electron passes its energy to the phonons, is called Shockley–Read–Hall recombination and when a relaxing electron passes its energy to another electron or hole is called Auger recombination. From PL data, intensity, line edge, and FWHM are the characteristics parameters i.e. higher intensity means low defect density and greater FWHM gives poor structure and vice versa. In addition to all the above, the energy bandgap calculation from PL data is subject to many limitations. For example, PL emissions do not give an exact bandgap like UV-Vis absorbance (Tauc plot). The bandgap calculated by the PL study will always be less than the original bandgap. Emission spectra are usually solvent dependent and are shifted with the change in solvent polarity due to solvent relaxation, the excitation spectra are usually preferred for bandgap calculations.

In the following video, I have explained all the above discussions in detail. Links to the files used in the Origin tutorial video have been provided in the video description. Thanks

https://youtu.be/WCPSil8uryg