|Components of a thermoelectric device.||Sample holder of the Autoscreen measuring apparatus with automated sample feed.|
The assignment: automated measuring stationThe specific electrical conductance, the type of charge carrier (i.e. the doping) and the Seebeck coefficient play an important role in many sectors of industrial and university materials research. These physical properties are key parameters in research and production of solar cells, semiconductor components, organic semiconductors, LEDs, and thermoelectric modules – to name but a few.
Consequently, the determination of these data constitutes a crucial factor in material development and the subsequent quality control during production. Thus, lengthy waiting times for measurement results as well as labor-intensive measuring systems are a restrictive factor.
For this reason a fast and precise screening measuring setup with automated operation was developed at Fraunhofer IPM for the combined determination of the specific electrical conductance, the type of charge carrier and the thermal power.
The advantages: flexible, cost-efficient, easy to operate
This automated measuring system has been designed as a flexible, low-cost and easy-to-operate analysis measuring station at room temperature. The measurement is controlled, logged, and evaluated by user friendly software. The measuring system can be specifically tailored to the needs of the user.
The solution: automated individual measurementsThe sample holder is designed in such a way that it can hold several samples of different sizes and allows individual adjustment of the measuring probes to the expected samples. The determination of the electrical conductance is based on the van der Pauw method and is thus independent of the sample geometry – as is the measurement of the Seebeck coefficient.
For sufficiently small temperature differences, the resulting thermoelectric voltage is determined and the Seebeck coefficient ascertained from this. Using this coefficient, the type of charge carrier (n- or p-type semiconductor) of the material under test can be deduced.
Quality control: counterbalancing errors via the softwareVirtually all samples – regardless of whether they are solid material or thin film samples– can be characterized by the special design of the measuring system. As well as the temperature stability and the special thermal construction of the sample holder, the specific design of the measuring probes is crucial for a precise measurement.
The software developed at Fraunhofer IPM enables measurement errors (that are mostly caused by poor thermal or electrical contacting) to be detected and eliminated.
|Measurement setup in full view.|