Highly-stable and efficient polymer solar cells incorporating nanoscale buffer layers induced by spontaneous vertical phase separation

A nanoscale interlayer formed through spontaneous vertical phase separation enhances the efficiency and stability of polymer solar cells. Poly(ethylene glycol) molecules blended into the photoactive layer spontaneously migrate to the surface of the polymer blend to form the interfacial buffer, thereby reducing the contact resistance after undergoing chemical reactions with the Al atoms of the cathode. The vertical phase separation of PEG molecules in the device were investigated by using scanning electron microscopy and atomic force microscopy.