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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

THERMAL INSTABILITIES OF CHARGE CARRIER TRANSPORT IN SOLAR CELLS BASED ON GAAS PN JUNCTION

Josefa Ibaceta-Jaña
Department of Mechanical Engineering, University of Chile, Santiago 8370456, Chile

Williams Calderon-Munoz
Department of Mechanical Engineering, Universidad de Chile, Beauchef 851, Santiago, Chile

C. Jara-Bravo
Department of Mechanical Engineering, University of Chile, Santiago 8370456, Chile

Abstract

Among the factors that negatively affect a solar photovoltaic cell is high temperature. Either due to imperfections of the material or to non-uniform operating conditions, it is possible to have a decrease in local resistance and consequently an increase in electric field, what causes that heat concentrates in an area, generating hot spots. Hot spot can stabilize, gradually generating degradation of the cell, decreasing its lifespan and efficiency. Otherwise, a phenomenon of an uncontrolled positive feedback, thermal runaway, can occur and it is catastrophic for the cell, disabling its correct local operation. Thermal runaway is characterized by an exponential behaviour of temporal evolution of the temperature in hot spots. The spot gets hotter but the temperature far away from it decreases as smaller currents are dissipated. In this paper a two-temperature 1D hydrodynamic model is developed on a GaAs PN junction, considering non-thermal equilibrium state between lattice and charge carriers. The instability occurs in the PN junction and depends strongly on lattice boundary temperature. It is found that hot carriers and reducing device length can stabilize the system, increasing the time in which system temperature evolves to double its temperature.

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