O. Breitenstein, H. Straube
Within our cooperation with CSG Solar (Thalheim) we are investigating power loss mechanisms in CSG modules. Here the interpretation of lock-in thermograms is more complicated than for single solar cells, since the biases in the series-interconnected cells are floating. Therefore, in addition to lock-in thermography (see figure), we are using 2-D potential mapping to investigate the effect of a shunt on the whole module. Close-up thermograms of a cell in a CSG module (see figure) show a detailed structure that allows conclusions about area currents, edge shunting due to laser cutting, and thermoelectric heat transport (Peltier effect) from the contact holes to the p-n junction. We are also studying the basic heat conduction properties of thin film cells on glass and plastic substrate in lock-in thermography, as for these the expressions for standard cells are no longer valid.