Organic solar cells(OSCs) with the typical sandwich structure use the conjugated organic materials as the active layer to convert sunlight into electricity through the two electrode outputting current. These organic materials have the advantages of wide source

lightweight and renewable

causing that OSCs have attracted much attention in the field of clean renewable energy. The present research focus is still to enhance the power conversion efficiency (PCE) of OSCs mainly by improving the active layer materials

optimization of device structure and interfacial modification and so on. This paper mainly introduces the efforts of our group in interfacial engineering. We demonstrated highly efficient OSCs by incorporating the sulfonic acid or carboxylic acid functionalized hyperbranched polymers to modify the cathode interface. We reported the novel non-conjugated small molecule electrolytes as the interfacial layer for efficient OSCs to achieve high PCE up to 10.02% in single heterojunction conventional OSCs. We found that simple polar solvent treatment such as methanol could optimize morphology of the active layer and enhance the performance of the devices.