Cd and Co metal centered nicotinamide/nicotinic acid complexes were synthesized by chemical reactions. The complexes were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffractometer (P-XRD), ultraviolet–visible (UV–Vis) spectrometer, and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) detector. The complexes were used as interfacial layers in between Al and p-Si to fabricate Al/Cd-complex/p-Si and Al/Co-complex/p-Si metal semiconductor devices. The devices were characterized by current–voltage (I-V) and current-time (I-t) measurements under dark and various light power intensities. The ideality factor, barrier height, and series resistance values were extracted from I-V measurements and discussed in detail by various techniques. The I-t measurements were used to derive various detector parameters such as responsivity, photosensitivity, and specific detectivity for various power values and wavelength regions. The devices exhibited good photodiode and photodetector performance according to results, and they can be improved for optoelectronic applications.