Graphene-silicon based configurations are attracting great attention for their potential application as electronics and optoelectronics. For their practical use, it is still limited by the configuration fabrication process. In this paper, a catalyst-free method is reported to directly grow nanographene on silicon covered with a thin oxide layer to form nanographene-oxide-silicon configurations. Compared with previously reported nanographene-silicon Schottky junctions, the nanographene-oxide-silicon structures exhibit a high performance on electronic and photovoltaic properties. The reverse leakage current of the nanographene-oxide-silicon is suppressed from over 10(-5) A down to 10(-8) A and the rectifier ratio is greatly enhanced from less than 5 up to 10(3). The photovoltage is enhanced over 50 times. The nanographene-oxide-silicon structures exhibit especially ultrasensitive to weak light at a photovoltage working mode, which exceeds up to 10 6 V/W at the light power of 0.025 mu W. Due to the source material for nanographene is photoresist and the fabrication process is mainly based on the current-used photolithography and silicon technique, the developed nanographene-oxide-silicon structures are very easy for device fabrication, integration, and miniaturization, and could be a promising way to produce metal-free graphene-silicon based electronics and optoelectronics for commercial use.