We have investigated the illumination effect on electrical characteristics of nearly ideal Yb/p-Si Schottky diodes with a high zero-bias barrier height (phi(bo)). The value of reverse bias current increased as the illumination level increased for these diodes. The electrical parameters such as ideality factor (n) and phi(bo) were obtained as 1.09 and 0.80 eV in dark, respectively. n increases with increasing illumination level whereas phi(bo) decreases. The series resistance calculated using Cheung functions almost did not change with the illumination level. The characteristics of capacitance-voltage and conductance-voltage were obtained as a function of illumination level, applied bias voltage and frequency. The effect of illumination on the capacitance-voltage and conductance-voltage characteristics was clearly observed for 10 kHz frequency whereas the illumination did not affect the characteristics for 1 MHz frequency, significantly. The photovoltaic parameters such as open circuit voltage of 0.21 V, short circuit current of 1.60 x 10(-5) A, and fill factor of 62% were obtained for 1040 W/m(2). These values have changed with increasing illumination level. The effect of illumination on the density of the interfacial states was observed. The experimental findings have showed that the diodes are sensitive to illumination and have photovoltaic behavior. The Yb/p-Si Schottky diodes are promising for photodiode applications.