Low Work-function Poly(3,4-ethylenedioxylenethiophene): Poly(styrene sulfonate) as Electron-transport Layer for...

Low-work-function poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (

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

PSS films, thus substantially changing their charge selectivity from supporting hole transport to supporting electron transport. It was also found that the

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

PSS is used, PEIE-modified

PSS can considerably suppress device degradation because of the hydrophobic and alkaline nature of PEIE, which not only reduces the hygroscopicity of the

PSS but also neutralizes the acidic

PSS and thus prevents the corrosion of the ITO cathode. These results demonstrate the potential of PEIE-modified

PSS for use as an efficient ETL in commercial printed electronic devices.