Indium phosphide (InP) is preferred for the preparation of photovoltaic (PV) cells due to the optimum values of the band gap (1,35 eV), the high absorption coefficient of light (about 5·104cm-1, λ<900 nm) at direct optical transitions and behavioral peculiarities to the action of corpuscular radiation fluxes. The objective of the paper is to study the influence of the thicknesses of the intermediate poInP - epitaxial layer repeatedly deposited by the HVPE method [1], of n+CdS frontal layer deposited by the quazi-closed volume technique [2] and of the SiO2 antireflective layer on the electrical and photoelectrical properties of n+CdS-po-p+InP heterostructures. The study of I = f (U), C = f (U) dependencies of the n+CdS-po-p+InP heterostructures in the temperature range 77 ... 294 K had shown that the junctions are steep, the diffusion potential varies with temperature decrease from 0,89 V to 1,28V, the saturation current changes in the limits from 1,12x10^-9 Axcm-2 to 4,40x10^-9 Axcm-2, the space charge region width is of W = (0,34 ... 0,38) μm and the current flow is determined by tunneling at low temperatures (n >> 2) and recombination at room temperatures (n ~2). The load dependencies of the PV cells based on n+CdS-po-p+InP structures with different thicknesses of the intermediate po and of the frontal CdS layer given in Fig. 1, 2 have shown that the maximum efficiency values of 14,6% are achieved when poInP epitaxial layer thicknesses is of 4,5 ... 5 μm and of n+CdS frontal layer thickness is about 1 μm. The deposition of SiO2 antireflective layer allows to increase the n+CdS-p°-p+lnP PV cell short-circuit current by 15% from 29,2 mA⋅cm-2 to 34,4 mA⋅cm-2 and correspondinly to increase the efficiency of solar energy conversion into electricity.