(a) I–V characteristics of the rGO/n-Si photodetector device. The photoconductive current has been measured in reverse bias configuration. (inset) the I–V characteristics of the n-Si based substrate with and without laser light at 378 nm; (b) a proposed energy band diagram of the rGO/n-Si heterojunction under light illumination at reverse bias. The rGO bandgap is about 2.8 eV. The UV (blue arrow) and infrared (red arrow) radiation are reported. The penetration depth in the n-Si is of the order of 60 nm for a wavelength of about 378 nm and 10 µm for a wavelength of 685 nm.