Abstract
Polymer solar cells (PSCs) exhibit many advantages such as simple processing, flexibility and the potential to scale up to large area by using blade coating or ink-jet printing techniques. Interlayer mixing is one of the main problems for achieving PSCs with multilayer structure. In this study, we solved the problem by a buffer layer technique. The result showed that the technique which employs glycol as a buffer layer successfully circumvented the interlayer mixing and made the multi-layer devices achieveable with all-solution process. We also demonstrated that the device performance was greatly enhanced with a multi-layer structure.