Improving the performance of inverted polymer solar cells by the efficiently doping and modification of electron transport layer-ZnO

A novel ternary hybrid material zinc oxide & polyethyleneimine ethoxylated: reduced graphene oxide (ZnO&PEIE:RGO) is fabricated, and then used as electron transport layer (ETL) to improve the performance of inverted polymer solar cells (iPSCs). Compared with the pure ZnO as ETL, the power conversion efficiency (PCE) of iPSCs based on P3HT:PCBM blend system with ZnO&PEIE:RGO as ETL is efficiently improved from 3.00% to 3.83%. The addition of RGO increases the conductivity of ZnO, and the addition of PEIE not only passivates the surface of ZnO nanoparticles to reduce its surface defects , but also prevents the aggregation of the precursor dispersion of ZnO:RGO. Moreover, the performance of the PTB7:PCBM based iPSCs with ZnO&PEIE:RGO as ETL is also improved from 6.91% to 8.87% compared with that of the device with pure ZnO as ETL. Interestingly, devices with ZnO&PEIE:RGO also exhibit enhanced lifetimes devices with ZnO, which still retain up to 63% of their original PCE after stored for 30 days without any encapsulation in air. Consequently, this novel ternary hybrid material ZnO&PEIE:RGO is a promising ETL material for PSCs.