Polymer solar cells have gained much attention as they offer a potentially economic and viable way of commercially manufacturing lightweight, flexible and low-cost photovoltaics. Written by active researchers, the book provides a comprehensive overview of the recent advancements in polymer solar cell technology for both researchers and students that are interested in this field. The book covers several important topics that govern the photovoltaic property of polymer solar cells including 1) the chemistry and the design of new light harvesting and interfacial materials and their structure-property relationship; 2) the physics for photocurrent generation in the polymer solar cells; 3) new characterization tools to study morphology effect on the property of donor/acceptor bulk heterojunctions; 4) new device concepts such as tandem cells and semi-transparent cells and 5) advanced roll-to-roll processes for large-scale manufacturing of polymer solar cells.