Thermoacoustic analysis of solar cells by current modulation

The photoacoustic effect and a similar thermoacoustic effect with an alternating current (electroacoustic effect) are used to investigate the spatial distribution of heat sources in crystalline silicon solar cells. The use of a reference signal produced inside the same sample to normalize the acoustic signal allows background and photoacoustic cell effects to be reduced. The frequency dependence of these normalized measurements can be calculated analytically. Covering frequencies up to 10 kHz, the electroacoustic effect allows the nondestructive determination of diffusion lengths and recombination velocities at the interfaces. Volume and surface effects can thus be separated, which is useful for the analysis of high-efficiency solar cells.