Dear Filip,

let us short discuss the difference between PL and PLE. A PL (photoluminescence) spectrum exhibits a whole emission spectrum what is generated at a certain excitation wavelength. This spectrum contains a superposition of different excitations, like band-band transitions, excitons and so on.

An excitation spectrumworks as follows: You put your sensor (receiver monochromator) on a special emission wavelength - lets say you want to observe an exciton. Then you select from your emission spectrum the exciton recombination energy. After this you scan the excitation wavelength and you get a very selective spectrum for your exciton. Therefore is clear:

The photo excitation spectrum is a high selective method to study a certain excited state.

With Regard

R. Mitdank

Ideally PLE should be similar to the absorption spectrum. If not interesting stuff start to appear starting from trap states phonon Effects thermalization rotations and so on .....

Dear Filip,

PL is more appropriate to detect defects in solid. Because, if you don’t know the defect energy (defect level emission) it is difficult to acquire corresponding excitation profile. Whereas, if you know the band gap of solid, any excitation energy larger than Eg can be useful to obtain overall emission profile of the solid. If radiative defect states are there in the sample, it can be obtained from corresponding PL spectra.

Best Regards,

SS

Rüdiger Mitdank thank you for your answer. Supposing I have a sample with broad PL emission spectrum, almost featureless, from which I have vague information about electronic states in the sample, as I assume because of defects. Is there a benefit from using PLE on such a sample?

As I understand the cariers from edge of the bands/states should have enhanced recombination rate as a result of resonant excitation and should be easier to detect in PLE than in PL.

The second reason for which I thought resonant PLE is beneficial for sample with defects is following and I refered to it in my original question. Exciting carrier in non resonant way, moves carrier to excited states and leaves it with some kinetic energy, which has to be lost by interaction with lattice. In a semi classical picture, I imagined that since the excited carrier has to travel some distance before it thermalize, it increases the probability of being trapped by some defects. Therefore I concluded, that resonant PLE spectrum, should not be affected that much by defects as non resonant PLE and PL.

Kind regards