We present strategies for improving the power output of large-area pn-junctions for thermoelectric power conversion. The gradient of the pn-junction's built-in potential is used to separate thermally generated electron-hole pairs. An externally applied temperature gradient along the pn-junction induces a driving force to both electrons and holes which results in currents from the hot end to the contacts. Due to the exponential dependence of the thermal generation rate on the local temperature, the temperature distribution within the device strongly influences the device behaviour. We present simulation results describing the possible application of graded SiGe alloys in order to control the temperature distribution and thus improve the power output and efficiency of thermoelectric generators using large-area pn-junctions.

The ever-increasing number of connected objects requires novel ways to power them and make them fully autonomous. In this context, photovoltaic, piezoelectric or thermoelectric energy-harvesting technologies show great promises as...

We present a theoretical approach for the integer quantum Hall effect, which is able to describe the interplateau transitions as well as the transition to the Hall insulator. We find two regimes ͑metalliclike and insulatorlike͒ of the top Landau level, in which the dissipative bulk current appears in different directions. The regimes are separated by a temperature-invariant point. ͓S0163-1829͑98͒01447-7͔

The rising interest in low temperature heat energy conversion encourages the application of thermoelectric devices. However, conventional thermoelectric devices used in the Seebeck mode as thermoelectric generators have several shortcomings and thus are inefficient when used as a generator. Additionally, the high cost–power ratio of these modules anticipates the commercial success on a broad basis. One way to achieve better suited products is provided by miniaturization of thermoelectric devices in order to enable the use of mass production methods. But in small devices the contact effects become dominant and reduce the efficiency and power density considerably. We show that using pn‐junctions with thermal generation of free carriers offers the possibility to achieve better contact properties and thus higher efficiencies and power densities. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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