Heat flow measurements for solar cell analysis

Heat flow measurements can augment information obtained from electrical measurements on the operating mechanisms in semiconductor devices and particularly solar cells. These measurements can be carried out by a number of experimental methods. The results reported here have been obtained by use of the photoacoustic method, in which a periodic heat flow induces a pressure wave in a small chamber which encloses the device under test, or is attached to it. A microphone detects the pressure wave. The heat flow results from the losses connected with the operating mechanisms of the device. Variations of the operating parameters, such as applied voltage, incident light flux, and/or wavelength etc., permit separation of the mechanisms. Choosing appropriate frequency ranges for the excitation can yield determination of the distance of the heat sources from the surface of the device.