title: Demonstration and Analysis of the Photocurrent by absorption of two sub-bandgap photons in a quantum dot intermediate band solar cell creator: Antolín Fernández, Elisa creator: Martí Vega, Antonio creator: García-Linares Fontes, Pablo creator: Cánovas Díaz, Enrique creator: Fuertes Marrón, David creator: Luque López, Antonio creator: Farmer, C.D. creator: Stanley, Colin subject: Renewable Energy subject: Physics description: 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. publisher: E.T.S.I. Telecomunicación (UPM) rights: https://creativecommons.org/licenses/by-nc-nd/3.0/es/ date: 2008 type: info:eu-repo/semantics/conferenceObject type: Presentation at Congress or Conference source: CD-ROM Proceedings of the 23rd European Photovoltaic Solar Energy Conference | 23rd European Photovoltaic Solar Energy Conference | 01/09/2008-05/09/2008 | Valencia, España type: PeerReviewed format: application/pdf language: eng rights: info:eu-repo/semantics/openAccess identifier: https://oa.upm.es/3578/