Lateral thermal diffusion effects on photothermal signals from photovoltaic cells

Thermal diffusion, parallel to the photovoltaic junction and perpendicular to the direction of illumination, can be used to separate the contributions of injected and photogenerated carriers to the generation of heat in a pho tothermal experiment, and to demonstrate the influence of electronic carrie r diffusion on the signal, already at relatively low modulation frequencies . We show this by using an experimental arrangement in which the distance i s varied between the illuminated area of the photovoltaic cell and that ove r which the thermal signal is detected, and the two areas do not overlap. O ur results agree with theoretical calculations used to simulate the phototh ermal responses of solar cells.