In this work, Cu doped SnS2 nanoflakes were synthesized through a simple hydrothermal method. The influence of Cu doping on the structural, optical and electrical properties of SnS2 were investigated in detail. Optical properties explores the Cu doping in SnS2 crystal lattice to result with a red-shift in absorption spectrum, which benefits visible-light absorption. Photodiodes were further fabricated by spin coating Cu doped SnS2 nanoflakes on p-type silicon (Si). Electrical and photoelectrical parameters of Cu doped SnS2 nanoflakes were determined by studying their impedance and current-voltage (I-V) characteristics, respectively. The diodes were found to exhibit excellent rectifying behavior and good sensitivity on par to pristine photodiodes. Impedance results identified the resistance of device to reduce considerably on Cu doping. The enhanced photoelectrical properties of the heterojunctions has been ascribed to Cu ions, which act as effective dopant and contribute to the varied carrier concentration in SnS2. Finally the obtained results suggest the potential of Cu-doped SnS2 for application in photodetection and sensors applications.