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On the reported experimental evidence for the quasi-Fermi level split in quantum-dot intermediate-band solar cells

Authors


Correspondence: Ahmed A. Abouelsaood, Dept. of Engineering Math. and Physics, Faculty of Engineering, Cairo University, Giza, Egypt.

E-mail: aelsaood@aucegypt.edu

ABSTRACT

The reported experimental evidence for the quasi-Fermi level split in quantum-dot intermediate-band solar cells is carefully examined. It is shown that the separation of the quasi-Fermi level of the intermediate band from that of the conduction band is not consistent with the experimental results of the quantum efficiency and the luminescence intensity of the InAs/GaAs cells. The fact that the electroluminescence spectrum is too wide, extending much further than we expect on the basis of the measured quantum efficiency in the direction of increasing photon energies, indicates that the temperature of the optically active regions of the cell during the electroluminescence measurements is considerably higher than room temperature. The best agreement with the experimental results is achieved with a temperature of about 525 K. This temperature rise is probably a result of the heating effect of the relatively high forward current used in the luminescence experiments. It is argued that the lack of a quasi-Fermi level split in this case is associated with the absence of a gap in the emission/absorption spectrum of sub-bandgap photons. Copyright © 2011 John Wiley & Sons, Ltd.

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