Passivation of InAs quantum dots for novel photovoltaics

Novel photovoltaic device designs offer the possibility of limiting efficiencies well in excess of conventional limits [1,2]. Many of the suggested devices rely on the inclusion of nanostructures in order to improve conventional energy conversion mechanisms or allow new mechanisms to be exploited. Because nanostructures rely on quantum confinement realized by heterojunctions, strain induced defects at hetero-interfaces, and the non-ideal recombination pathways they bring, need to be passivated, in order for the novel devices to operate as intended. We report attempts to passivate quantum dots in the much studied InAs/GaAs system using a Sb flux treatment immediately prior to capping of the quantum dots with GaAs. The photoluminescence results suggest an optimum exposure time to the Sb flux after which the performance degrades substantially. Temperature dependent photoluminescence results as well as X-ray diffraction results are also presented in order to explain the structure at the quantum dot - cap interface. The impact of these results in terms of the design of two novel photovoltaic devices, the intermediate band solar cell and the hot carrier solar cell is also discussed.