Water/Alcohol Soluble Thickness-Insensitive Hyperbranched Perylene Diimide Electron Transport Layer Improving the Efficiency of Organic Solar Cells.

The electron transport layer (ETL) is very crucial for enhancing the device performance of polymer solar cells (PSCs). Meanwhile, thickness-insensitive and environment-friendly water/alcohol soluble processing are two essential requirements for large-scale roll-to-roll commercial application. Based on this, we designed and synthesized two new n-type ETLs with tetraethylene pentamine or butyl sulfonate sodium substituted tetraethylene pentamine as the branched side chains and high electron affinities perylene diimide (PDI) as the central core, named as and . Encouragingly, both and can effectively reduce the interfacial barrier and improve the interfacial contact. In addition, both of them can exhibit strong n-type self-doping effects, especially the with higher density of negative charge. Consequently, compared to bare ITO, the PCE of the devices with ITO/ and ITO/ ETLs has increased to 3-4 times. Our research results indicate that n-type self-doping PDI-based ETL and could be promising candidates for ETL in environment-friendly water/alcohol soluble processing large-scale PSCs.