Multi-stacked InAs/GaNAs quantum dots with direct Si doping for use in intermediate band solar cell
We investigated the effect of direct doping of quantum dots (QDs) with Si on the performance of QD solar cells (QDSCs). In order to control the Fermi level of intermediate band (IB) region, 25 layers of stacked InAs/GaNAs QDs were directly doped with Si impurity during the self-assembling stage of growth. A QDSC with Si doping shows an improved quantum efficiency (QE) in shorter wavelength region, which is from p-GaAs emitter layer. Further, the fact that applied external bias does not affect QE spectrum as well as photocurrent in QDSC with Si direct doping suggests that carrier collection has been enhanced in QD region as a result of reduction of recombination.
Current enhancement in direct-doped InAs/GaNAs strain-compensated quantum dot solar cell
We investigated the effect of direct Si-doping of self-organized quantum dots (QDs) in molecular beam epitaxy (MBE) on the performance of QD solar cells (QDSCs). In order to control the quasi-Fermi level of intermediate band (IB) region, 25 stacked layers of InAs/GaNAs QDs were directly doped to n-type with Si during the self-assembling stage of growth. The amount of doping of each InAs QD layer was changed from 5 × 10<sup>10</sup> cm<sup>−2</sup> (one electron per QD) to 25 × 10<sup>10</sup> cm<sup>−2</sup> (five electrons per QD). Improved quantum efficiencies (QE) and photovoltaic properties were achieved for QDSC with doping density of 5 × 10<sup>10</sup> cm<sup>−2</sup> under an irradiation of AM1.5 solar spectrum. Increasing the doping density above the optimum resulted in a degradation of QE and PV properties. In QDSC with a doping density of 5×10<sup>10</sup> cm<sup>−2</sup>, or one electron per QD, a photocurrent production due to two-step photon absorption was measured at room temperature detected under filtered air-mass 1.5 solar spectrum.
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.