Effective Double Electron Transport Layer Inducing Crystallization of Active Layer for Improving the Performance of Organic Solar Cells

Interface modification plays an important role in enhancing the photoelectric conversion efficiency and stability of organic solar cells. In this work, alkali metal lithium chloride (LiCl) was introduced between indium tin oxide and polyethyleneimine ethoxylate (PEIE) to prepare a double-layer electron transport layer. Results show that the introduction of LiCl has dual functions. The first function is that LiCl can enhance conductivity, thereby facilitating charge collection. The second function is that the double-layer electron transport layer based on LiCl can induce the crystallization of active layer, thereby enhancing charge transport. Devices with LiCl/PEIE double layer achieve a high power conversion efficiency (PCE) of 3.84%, which is 21.5% higher than that of pristine devices (the PCE of pristine devices with pure PEIE interface layer is 3.16%).