Effect of Interfacial Oxide Layers on Self-Doped PEDOT/Si Hybrid Solar Cells

PEDOT:PSS/Si hybrid photovoltaic cells have been attracting attention as a potential way to simplify the manufacturing process and democratize solar energy production. Control of the PEDOT/Si interface is also one of the primary ways to ensure the improved performance and lifetimes of multijunction devices, such as perovskite/Si tandem solar cells. In this work, the effects of the interfacial silicon oxide layer were investigated by creating a novel and controllable neutral beam oxide interlayer with different thicknesses. A novel self-doped PEDOT (S-PEDOT) was used to improve interfacial contact and avoid the secondary doping of PEDOT:PSS. X-ray photoelectron spectroscopy (XPS) showed that the saturation of interfacial silicon atoms in SiO_x-Si bonds as well as a very thin, (~1 nm) damage-free oxide interlayer were the keys to maintaining good passivation with a high tunneling current. Lifetime measurements also showed that the interlayers with the most SiO₂ content degraded the least. The degradation of the devices was due to the continued growth of the oxide layer through reactions with silicon sub-oxides and the degradation of S-PEDOT.