We were produced a various Mn-doped complex and presented it in Au/Mn-complex/n-Si structure as an interfacial layer. For this aim, a metal-nicotinate/nicotinamide mixed ligand complex was synthesized with Mn dopant. Surface morphologies were investigated using surface analysis methods (AFM and SEM) and relatively smooth and uniform surfaces were obtained for each doping level. The devices were characterized using current–voltage and time-dependent photoresponse measurements. In order to examine the response to light, the measurements were carried out in the dark and different lighting (from 20 to 100 mW/cm2) intensities. With the increasing amount of Mn dopant, the barrier heights and junction resistance of devices were decreased. Increasing the amount of light was increased the sensitivity of the devices to the light. The highest photoconductivity was recorded for 1 mg Mn-complex. It was seen from obtained results, the fabricated devices exhibited good photodiode behavior and can be used in optoelectronic applications.