Solar cells based on the photovoltaic effect are the source of energy which compete with known fossil fuel sources and another renewable energy sources. According to the Plank’s law, estimated efficiency of solar energy conversion may reach in the ideal case up to 93%. However, many physical and technical restrictions significantly decrease this perfect value. The Shockley-Queisser limitations show the possible boundaries for energy production using photovoltaic effect. At the same time, many researchers in the world are looking for the ways to circumvent these limitations. Various possible ways for improvement of solar cells efficiency are considered in this review. Specific attention was applied to plasmon enhanced solar cells.