In this work, the current-voltage and photoelectric spectral characteristics of double heterodiodes por-Si/Si-p/Si-n and a reference diode with a p–n junction at room temperature are analyzed and compared with data on the thickness of porous silicon layers and photoluminescence spectra for the synthesized heterostructures. It is shown that photospectral sensitivity in the region of 400–800 nm is exhibited by diodes with a single-layer structure of porous silicon whose thickness does not exceed 2 µm. In this case, the amplitude of the spectral photoresponse decreases with a decrease in the thickness of the porous layer. As for diodes with a two-layer structure of porous silicon (ordinary porous and tree-like porous) and thicknesses from 4.5 µm to 17.4 µm, currents do not flow due to rapid oxidation of such structures. A band energy diagram of a double heterodiode with a layer of porous silicon is proposed based on the experimental data.