Determination of thermophysical properties of thin films for photovoltaic applications

The thermophysical properties of thin film materials used for photovoltaic applications are investigated. The measurement procedure that we apply is described in detail. The method is based on a contact-free thermal analysis of free standing thin films using a lock-in thermography system. A laser heat source induces a thermal wave that propagates within the sample. An infrared camera images the wave. From the resulting temperature amplitude and phase images of the wave, the in-plane thermal diffusivity, thermal conductivity, and volumetric heat capacity are deduced. The investigated samples are compound and laminating foils employed in photovoltaic (PV) module encapsulation, as well as a plastic substrate used for thin film solar cell production. The measurement results show large differences in the thermal conductivity of different types of compound materials.