Photovoltaic conversion is a process for the direct conversion of sunlight into electricity. This book is a survey of recent achievements in solar concentration techniques for photovoltaic electricity generation and the authors draw on Russian research into photovoltaics. The text includes research in this field, including: luminescent phenomena in relation to semi-conductor concentrators; analysis of new developments in semi-conductor materials and cascade semi-conductors; and problems in the use of photovoltaics caused by an irregular lack of sunlight density.