Engineering of Interfacial Electron Transfer from Donor–Acceptor Type Organic Semiconductor to ZnO Nanorod for Visible-Light Detection

Abstract

Interfacial electron transfer (IET) plays a key role in photoactive organic/inorganic hybrid nanomaterials and remains elusive with regard to interfacial energy level alignment. In this study, we prepared hybrid ZnO nanorods by grafting n-type perylene bisimide (PBI) derivatives bearing carboxylic acid groups at nitrogen positions. No evidence in terms of direct electron transfer from PBI to ZnO can be observed in PBI/ZnO hybrids. In sharp contrast, incorporation of electron-rich oligothiophene (<i>n</i>T, <i>n</i> = 1, 2) moieties into PBI core at bay positions resulted in a highly efficient cascade IET in <i>n</i>T-PBI/ZnO (<i>n</i> = 1, 2) hybrid nanorods, which was initiated by photoinduced electron transfer (PET) from <i>n</i>T (<i>n</i> = 1, 2) to PBI and then followed by charge shifting from PBI anion to ZnO across the interface. High performance UV–vis photodetectors based on <i>n</i>T-PBI/ZnO (<i>n</i> = 1, 2) hybrids have been fabricated and show responsivity of 21.2 and 12.4 A/W and an on/off ratio as high as 537 and 403, whereas that based on PBI/ZnO shows little visible-light response. Our results suggest that donor–acceptor type compounds can be used for constructing photoactive hybrid nanomaterials, in which efficient cascade IET modifies interfacial electronic structure and helps extend the spectral response range