%0 Conference Paper
%A Antolín Fernández, Elisa
%A Martí Vega, Antonio
%A García-Linares Fontes, Pablo
%A Cánovas Díaz, Enrique
%A Fuertes Marrón, David
%A Luque López, Antonio
%A Farmer, C.D.
%A Stanley, Colin
%B 23rd European Photovoltaic Solar Energy Conference
%C Valencia, España
%D 2008
%F upm:3578
%I WIP-Renewable Energie
%K High Efficiency; Intermediate Band; Quantum Dots
%T Demonstration and Analysis of the Photocurrent by absorption of two sub-bandgap photons in a quantum dot intermediate band solar cell
%U https://oa.upm.es/3578/
%X In order to surpass the efficiency limit of single gap solar cells, intermediate band solar cells (IBSC)  have to fulfill two requirements: the production of extra photocurrent by absorption of sub-bandgap photons in  electronic transitions involving the intermediate band (IB) and the preservation of a high output voltage, not limited  by the existence of this band. This work presents experimental evidence of the production of electron-hole pairs by  absorption of two sub-bandgap photons in IBSC prototypes fabricated with InAs/GaAs QD material. The  experiments were carried out at low temperatures using a specifically designed modulated photocurrent measurement  set-up with two light beams. The results are analysed with the help of a simple equivalent circuit model. This  analysis is also used to highlight the relevance of the two-photon mechanism demonstrated in the experiment. It is  discussed that, although the absorption of sub-bandgap photons in one of the IB transitions and subsequent thermal  escape of carriers is a sufficient mechanism to obtain a photocurrent enhancement, the absorption of sub-bandgap  photons in both transitions involving the IB is a requisite for the voltage preservation in IBSCs.