Donor–acceptor bulk heterojunction polymer solar cells are currently showing power convention efficiency of more than 6%. Thermal annealing, slow drying, additive processing, controllable self-assembly morphology, adding buffer layer and new device structure can play an important role in achieving high power convention efficiency. In order to obtain more than 10% of power convention efficiency from single layer polymer solar cells, more investigation must be carried out to explore the fundamental mechanisms and develop new materials. Development of new materials is an urgent issue. Many scientists believe there is a best way to get more absorption and higher open circuit voltage, and a better charge transfer condition. Toward a controllable interpenetrating network in the films is also important for optimization of solar cell performance. In addition, designing novel structures to gain more absorption and controllable local order of materials are possible approaches to realize high efficiency and high stability of polymer solar cells.