A photovoltaic cell with carbonaceous thin film/n‐type silicon (C/n‐Si) was fabricated. The carbonaceous thin film was deposited on an n‐type single‐crystal‐silicon substrate by chemical‐vapor deposition of 2,5‐dimethyl‐p‐benzoquinone at 500 °C. Without light irradiation, the photovoltaic cell displayed an almost perfect rectifying current–voltage characteristic. Under illumination of 15 mW cm−2 light with wavelengths between 400 and 800 nm similar to the solar light, it generated 2.73 mA cm−2 of short‐circuit and 325 mV of open‐circuit voltage. With the same light condition, a power conversion efficiency of 3.80% and a fill factor value of 0.65 were achieved.