Publications (6)6.01 Total impact
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Article: Emitter degradation in quantum dot intermediate band solar cells
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ABSTRACT: The characteristics of intermediate band solar cells containing 10, 20, and 50 InAs quantum dot (QD) layers embedded in otherwise “standard” (Al,Ga)As solar cell structures have been compared. The short-circuit current densities of the cells decreased and the quantum efficiencies of the devices showed a concomitant reduction in the minority carrier lifetime in the p emitters with increasing number of QD layers. Dislocations threading up from the QDs toward the surface of the cells, and revealed by bright field scanning transmission electron microscopy, are the most likely cause of the deterioration in the electrical performance of the cells.Applied Physics Letters 07/2007; · 3.84 Impact Factor -
Article: Operation of the intermediate band solar cell under nonideal space charge region conditions and half filling of the intermediate band
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ABSTRACT: A photovoltaic device based on an intermediate electronic band located within the otherwise conventional band gap of a semiconductor, the so-called intermediate band solar cell (IBSC), has been proposed for a better utilization of the solar spectrum. Experimental IBSC devices have been engineered using quantum dot technology, but their practical implementation results in a departure of key underpinning theoretical principles, assumed to describe the operation of the IBSC, away from the ideal. Two principles which are only partially fulfilled are that (i) the intermediate band should be half filled with electrons and (ii) the region containing the quantum dots should not be located fully within the junction depletion region. A model to describe the operation of the devices under these nonidealized conditions is presented and is used to interpret experimental results for IBSCs with ten layers of quantum dots. Values for the electron and hole lifetimes, associated with recombination from the conduction band to the intermediate band and from the intermediate band to the valence band (0.5 and 40 ps , respectively) are thus obtained.Journal of Applied Physics 06/2006; · 2.17 Impact Factor -
Article: Production of photocurrent due to intermediate-to-conduction-band transitions: A demonstration of a key operating principle of the intermediate-band solar cell
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Article: Application of Fourier Transformation infrared spectroscopy to the characterization of the intermediate band solar cell optical transitions
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Article: Low temperature characterization of the photocurrent produced by two-photon transitions in a quantum dot intermediate band solar cell
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ABSTRACT: Conceived to exceed the conversion efficiency of conventional photovoltaic devices, the intermediate band solar cell bases its operation on exploiting, besides the usual band-to-band optical transitions, the absorption of two sub-bandgap photons. For the present, the only technology used to implement an intermediate band in real devices has been the growth of an InAs/GaAs quantum dot superlattice. In practice, the obtained material shows two limitations: the narrow energy gap between conduction and intermediate band and the appearance of growth defects due to the lattice stress. The consequences are the presence of non-radiative recombination mechanisms and the thermal escape of electrons from the intermediate to the conduction band, hindering the splitting of the quasi-Fermi levels associated with the intermediate and conduction bands and the observation of photocurrent associated with the two-photon absorption. By reducing the temperature at which the devices are characterised we have suppressed the parasitic thermal mechanisms and have succeeded in measuring the photocurrent caused by the absorption of two below bandgap photons. In this work, the characterization of this photocurrent at low temperature is presented and discussed. -
Article: Progress in quantum-dot intermediate band solar cell research
