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23 September 2016 Evidence of suppressed hot carrier relaxation in type-II InAs/AlAs1-xSbx quantum wells
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Hot carrier solar cells (HCSCs) have been proposed as devices, which can increase the conversion efficiency of a single junction solar cell above the Shockley-Queisser limit. For practical implementation of such systems, solar cells operating with efficient hot carrier extraction must circumvent two fundamental challenges: 1. Find an absorber material in which hot carriers are sustained either via inhibiting or circumventing phonon relaxation pathways; 2. Implement energy selective contacts in which only a narrow range of energy within the hot carrier distribution is extracted; thereby, reducing cooling losses in the contacts.

Here, type-II InAs/AlAs0.16Sb0.84 quantum-wells are investigated as a candidate system for hot carrier absorbers. Continuous wave power and temperature dependent photoluminescence measurements are presented that indicate: a transition in the dominant hot carrier relaxation process from conventional phonon-mediated carrier relaxation − below 90 K − to a regime where inhibited radiative recombination dominates the hot carrier relaxation − at higher temperatures1. The reduction in the PL efficiency is strongly coupled to an increase in the hot carrier temperature extracted from the measurements. This behavior is attributed to a build-up of electrons in the QWs, which appears to inhibit electron-phonon relaxation2.
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V. R. Whiteside, H. Esmaielpour, J. Tang, S. Vijeyaragunathan, T. D. Mishima, M. B. Santos, B. Wang, R. Q. Yang, and I. R. Sellers "Evidence of suppressed hot carrier relaxation in type-II InAs/AlAs1-xSbx quantum wells", Proc. SPIE 9937, Next Generation Technologies for Solar Energy Conversion VII, 993709 (23 September 2016);

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