This book presents the details theory about Nano technology, Thin films deposition process & practical application of thin films in different types of solar cells. In chapter three, Basic structure of solids, their classifications, Lattice, Basis & Miller indices has been discussed. In chapter four, thin film deposition methods, substrates, solutions preparation, growth mechanisms, advantages, disadvantages & application has been discussed. In chapter five, detailed theory about Spin coating, Spray pyrolysis etc & their growth mechanism, advantages, disadvantages, practical applications has...