Feasibility study of a hot carrier photovoltaic device

Abstract : A hot carrier solar cell is characterized by a carrier population in thermal non equilibrium with the lattice, that translates into carriers having a temperature higher than the material temperature. It then becomes possible to collect not only the carrier potential energy but also their kinetic energy, and thus to extract an additional power that is not used in conventional solar cells. This enables to reach a potential efficiency close to the thermodynamical limit. The extraction of carriers is made through energy selective membranes in order to reduce the heat loss. In this thesis, the impact of contact selectivity on the cell behaviour is investigated by simulating its efficiency. It appears that this parameter is not as crucial as what was said in the literature, and that a high efficiency is indeed possible with semi-selective contacts allowing carrier extraction above an energy threshold. Such contacts would not only be much easier to fabricate in practice, but are also more compatible with the high current densities that are expected in such devices. An experimental method is also proposed to determine the non equilibrium carrier cooling rate. Carriers are photogenerated by a continuous wave laser and their temperature in steady state conditions is probed by photoluminescence as a function of the excitation power density. An empirical model is obtained that relates the power dissipation due to carrier thermalization to the electron temperature. Such model can then be used in a hot carrier solar cell model to take heat losses into account. Finally, the efficiency of a realistic cell having non ideal absorption, a cooling rate measured on real materials and semi-selective contacts is simulated. It turns out that a substantial efficiency enhancement is possible compared to single junction cells with the same band gap, but that the cooling rate measured on samples is nevertheless too high to exceed today's efficiency records. Ideas are proposed to improve the performance of the structure under investigation.
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Submitted on : Wednesday, June 27, 2012 - 3:54:55 PM
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  • HAL Id : pastel-00712642, version 1

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Arthur Le Bris. Feasibility study of a hot carrier photovoltaic device. Electric power. Ecole Centrale Paris, 2011. English. ⟨pastel-00712642⟩

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