All processes of charge carrrier separation and current formatiopn in CdS/CdTe solar cells occur in CdTe layer, therefore it plays a crucial role in the assuring of high efficiency of the given heterostructures. The formation of a tunnel-transparent CdO nanolayer between CdS and CdTe layers leads to the enhancing of SC energetic parameters.  CdS-CdTe heterojunctions were obtained by sccessive of CdS and CdTe layers on the glass substrates (2X2cm²) covered by a conducting (~10^-3 Ω.cm) transparent SnO₂ layer by using quasi-closed volume method. CdS thin layer had the thickness of 0,3÷0,6 μm and the electrons concentration 1,6÷2,3.10¹⁸cm^-3, CdTe layers had the thickness of 8÷14 μm and the holes concentration of ~(2÷8).10¹⁵cm^-3.  Before the deposition of CdTe layer a CdO layer with the thickness of 2 ÷50 nm was deposited on to the CdS layer surface. CdO layers were obtained by magnetron sputtering at a constant current intensity of Cd targetin the atmosphere of oxygen.The CdO layer thickness was controled by the time of sputtering and was determined by using a graduated curve of layer thickness dependence on the sputtering time.  As it was shown by the measurements of I-U dependencies in the dark, the introduction of tunnel CdO layer does not change the feature of current flow in CdS-CdTe structure and influences the current value only. The main characteristic parameters of CdS-CdTe heterojunctions with the tunnel-transparent CdO layer and without it, fabricated in the same technological cycle are given in the Table below. At the direct biases the current exponentialy depends on the applied voltage and on the the inversely temperature. The ideality factor decreases from 3,4 at 283K to 1,6 at 383K. The saturation current exponentialy depends on temperature with activation energy E_a =0,62 eV.Hence at the direct biases the current flow in CdS-CdO-CdTe structures is determined by the recombination in the space charge region through the recombination centre with the energy of 0,62 eV.   At the reverse biases the current depends on the applied voltage according to the power function (I_rev.~ U^m). Up to the voltages of 0,4÷0,5 V the index m ~1, which indicates the the leakage currens predominate, and at higher voltages m=2÷3. The reverse current exponentialy depends on temperature with activation energy 0,615 eV. At the reverse biases the current flow is stipulated by the generation processes through the same impurity level as the direct current.  At 300K the CdS-CdO-CdTe structures illumination with the integral light the open circuit (U_oc) tends to saturation and and short circuit current (I_sc) grows proportionaly to the light flow. The photoelectrical parameters of SnO₂-CdS-CdO-CdTe-Ni structures with the optimum values of CdO layer thickness (5÷8) nm at 300K and the illumination power 100 mW/cm² have the values: U_oc=0,79÷0,83 V, I_sc=24,6÷24,8 mA/cm², FF=0,54÷0,57, ŋ=11,1÷11,8% .  The spectral sensitivity of SnO₂-CdS-CdO-CdTe-Ni structures covers the wavelength region 0,52 ÷0,86 μm and is constant which indicates tolow concentration of the recombination centres at the heterostructure interface. Introduction of CdO layer with a thickness of 5 ÷8 nm increases the spectral sensitivity by 1,4÷1,7 times.