Comparative Study on Planar-silicon and Nano-silicon Si/PCBM Inorganic-organic Hybrid Junctions

Abstract

Inorganic-organic heterojunction devices based on organic polymer and inorganic semiconductors has attracted extensive attention for high performance hybrid solar cell applications, due to the combined advantage of high carrier mobility of inorganic semiconductors and easy processing, strong absorption of organic polymers. In this study, both planar-Si and nano-Si were combined with spin-coated (6, 6)-phenyl C61-butyric acid methyl ester (PCBM) organic film to form Si/PCBM inorganic/organic hybrid junctions. A comparative study was per- formed through quantitative electrical analysis of planar-Si/PCBM and nano-Si/PCBM, respectively. In general, both devices exhibited a rectifying diode-like behavior. However, a higher turn-on voltage and smaller current density were observed from nano-Si/ PCBM junctions, which was in contradiction with the expectation from the view of junction area. The corresponding mechanisms were further investigated with measurements of impedance spectroscopy (IS). Our results indicated that this abnormal electrical characteristic of nano-Si/PCBM compared with normal p-n junction was highly associated with the parasitic effects caused by the defect states at the junc- tion interface.