"This project proposes an experimental investigation on the basic material physics and the feasibility of the intermediate band solar cell (IBSC), which is a new type of photovoltaic device with the potential for very high conversion efficiencies and low spectral sensibility. The operation of the IBSC relies on the use of a light absorbing material that differs from a conventional semiconductor by having an intermediate band (IB) of allowed electron states within the band gap. According to the theoretical model, a p-IB material-n solar cell can render a higher photocurrent than a comparable p-n structure, without significant degradation of the voltage. The work to be performed in this project comprises the production (epitaxial growth) of IB material samples and devices, and their characterization. The approach proposed is to focus on a well-known material as semiconductor host (GaAs). The IB materials will be synthesized by introducing high densities of a transition metal impurity, such as Fe or Co, in that host. The characterization tools will include time-resolved photoluminescence, electrical transport measurements and optical absorption spectroscopy. The main results expected from the project are: (a) to assess the feasibility of a material with a sufficiently high impurity content so as to exhibit the predicted properties of an IB material, whilst maintaining a sufficient crystalline quality (with emphasis on the radiative/non-radiative recombination properties); (b) to characterize the IB electrical and optical properties correlating them to optimized growth conditions. To fulfil those objectives we rely on the wide experience of Prof. Foxon’s group at University of Nottingham on epitaxial growth of heavily-doped spintronic materials, as well as on the knowledge of the fellow on IB solar cells. This project addresses fundamental physics questions which are relevant to the photovoltaic industry and to the European future energy needs."
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