High efficiency of solar energy conversion is not possible without proper design of solar cells. Along with conventional structures based on crystalline silicon or wide band gap A3B5materials there are proposed solar cells of various architecture (for example, tandem solar cells) and solar cells fabricated using novel technologies. The paper presents the following types of high-effective solar cells: i) solar cells fabricated on high oxygen concentration single crystal silicon substrates grown by CZ-method with thin film silicon active layer for enhanced photoelectron conversion formed by ion implantation with optical coatings for advantageous coupling of solar radiation into thin film solar cell devices via the use of rare-earth metal oxide (REOx), rare-earth metal oxynitride (REOxNy) and rare-earth metal oxyphosphide (REOxPy) glasses and or crystalline material; ii) single p-n-junction solar cells including an alloy of either InGaN or InAlN formed on one side of the p-n-junction with Si formed on the other side in order to produce characteristics of a two junction tandem solar cell through only a single p-n junction are expected to achieve 30%power efficiency. Furthermore, the paper discusses necessary fundamentals of solar device functionality and describes important physical features of casings used in device design. Recent patents information on solar energy conversion is also discussed in this article.