Experimental observation of the photovoltaic effect of a semiconductor grain boundary with a scanning laser spot is analyzed assuming a single trap energy level. The current is calculated from the recombination velocity and the concentration of the minority carriers at the grain boundary which was derived from the continuity equation. The open‐circuit voltage across the sample is obtained from equating this recombination current to the compensating current using the thermionic emission model. Using the recombination velocity and the diffusion length as variables, the calculated open‐circuit voltage is compared with the experimental data.