There are several processes which might be responsible for temper

There are several processes which might be responsible for temperature quenching of the photoluminescence (PL) in Si-NCs, such as (a) carriers’ resonant/non-resonant tunneling out of Si-NCs to sites where the non-radiative recombination occurs [26], (b) thermal activation of carriers over the potential barrier Si/SiO2 (3.4 eV) [27], and (c) simply non-radiative band-to-band transition. Other potential mechanisms,

such as exciton dissociation (approximately 14 meV for bulk Si [28]) should rather be excluded from consideration in the case of Si-NCs since within the Si-NCs, there are no excitonic Crenigacestat levels other than the ones related to Si-NCs itself, where the Columbic interaction has been included in self-consistent calculations.

Thus, there are no additional levels to which the exciton could dissociate as in GSK2879552 clinical trial the case of bulk material. The only quenching energy which could be associated with exciton dissociation is one which moves one of the carriers to defect levels at the surface of Si-NCs over the potential barrier (process a or b). The only temperature-dependent emission-quenching mechanisms related to the excitonic nature of carriers confined within the Si-NCs can be due to different spin selection rules for different energy levels, which give the dark and bright states, which can be split Compound Library concentration in Si-NCs even with 20 meV [29]. In the case of erbium ions, PL quenching can be related Quinapyramine to back-transfer mechanisms [30], which should be,

however, very inefficient in Si-NCs because of the large difference in Er3+ emission energy and the absorption edge of Si-NCs [31]. Another common mechanism responsible for the quenching of PL originating from Er3+ is Auger recombination between excited Er3+ and excess electrons bound to a surface/defect state at Si-NCs [32]. Finally, Er3+ can transfer energy due to dipole-dipole interactions to other ions or to defect states which play the role of quenching centers. In order to be temperature-dependent, all these quenching processes should be phonon assisted. In view of the above discussion, it can be seen that even if work on SRSO: Er3+-based LEDs is already advanced [7] from the fundamental point of view, there are many uncertainties and contradicting results in the literature. We believe that one of the main reasons is simplification of the interpretation of the obtained emission signal as related to Si-NCs only and the unappreciated role of the complex nature of the SRSO film where defects and both aSi-NCs and Si-NCs can be optically active simultaneously in the same spectral range. Moreover, in many cases, the 488-nm line is used for SRSO:Er3+ excitation, where this wavelength overlaps with one of the optical transitions of Er3+ ions and can bring about interpretation of obtained data.

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