@inproceedings{upm3578,
       booktitle = {CD-ROM Proceedings of the 23rd European Photovoltaic Solar Energy Conference},
           title = {Demonstration and Analysis of the Photocurrent by absorption of two sub-bandgap photons in a quantum dot intermediate band solar cell},
          author = {Elisa Antol{\'i}n Fern{\'a}ndez and Antonio Mart{\'i} Vega and Pablo Garc{\'i}a-Linares Fontes and Enrique C{\'a}novas D{\'i}az and David Fuertes Marr{\'o}n and Antonio Luque L{\'o}pez and C.D. Farmer and Colin Stanley},
         address = {Munich, Alemania},
       publisher = {WIP-Renewable Energie},
            year = {2008},
        keywords = {High Efficiency; Intermediate Band; Quantum Dots},
             url = {http://oa.upm.es/3578/},
        abstract = {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.}
}