Experimental analysis of the operation of quantum dot intermediate band solar cells

With a 63.2% theoretical efficiency limit, the intermediate band solar cell (IBSC) is a new photovoltaic device proposed to overcome the 40.7% efficiency limit of conventional single gap solar cells. Quantum dot technology can be used to take the IBSC concept into practice. In this respect, the results of experiments carried out recently to characterize IBSC solar cells containing different numbers of InAs quantum dot layers as well as the theoretical models used to describe and analyze the related experimental data are summarized here. Electroluminescence and quantum efficiency measurements confirm that the main operating conditions for IBSCs are complied with in structures with a low number of QD layers. These conditions include the production of photocurrent from absorption of below band gap energy photons and the formation of distinctive quasi-Fermi levels associated with each electronic band (i.e., the conduction, valence, and intermediate bands).