The analysis of the principle operation of the solar element is given in the work. The efficiency of the creation of combined high-efficiency converters of network energy in electric and thermal is indicated. A method for creating a combined photo thermo converter with a high value of the efficiency of a solar element has been found. A method for separating light from optical lenses is shown. The calculation of the light intensity into diffraction pattern is calculated using the Huygens-Fresnel principle. A new design of a highly efficient combined light-thermal converter into an electrical, with a solar element, operating on selective photoactive radiation is presented. The process of conversion of non-active radiation into electrical radiation by means of a thermo electronic converter is described. The ways of the solution of the problem connected with the reduction of the coefficient of its full effect as a function of temperature and characteristics are indicated.