Low-work-function poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (
Pedot: PSS) modified with polyethylenimine (PEIE) was used as an electron transport layer (ETL) for polymer solar cells (PSCs). A thin layer of PEIE film was spin-coated onto the surface on the
Pedot: PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the
Pedot: PSS/PEIE ETL exhibited higher interfacial contact, a more favorable active morphology, and improved charge mobility. By virtue of these beneficial properties, inverted PSCs based on low-bandgap semiconducting photoactive layers achieved a notably improved power conversion efficiency (PCE) of 7.94%, superior even to the corresponding performance of devices with only a ZnO layer. Surpassing our expectations, compared with the extreme degradation of device stability observed when pure
Pedot: PSS is used, PEIE-modified
Pedot: PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the
Pedot: PSS but also neutralizes the acidic
Pedot: PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified
Pedot: PSS for use as an efficient ETL in commercial printed electronic devices.