Noncovalent Molecular Heterojunction: Structure Determination and Property Characterization using Scanning Tunneling Microscopy/Spectroscopy and Theoretical Calculations

Noncovalent molecular heterojunctions (MHJs) formed by the stacking of p-type (electron donor) and n-type (electron acceptor) compounds are essentially important for various optoelectronics as well as molecular devices. Herein we report the construction of the fluorinated copper(II) phthalocyanine (F16CuPc; n-type, acceptor)–polymer NTZ12 (p-type, donor) MHJ via annealing of the film of F16CuPc and NTZ12. Scanning tunneling microscopy and density functional theory calculations validate the formation of the F16CuPc–NTZ12 MHJ at the single molecular level. The constructed MHJ shows a distinctive rectifying effect in the statistical data of scanning tunneling spectroscopy because of the different barriers in two directions of electron tunneling. In the proof-of-concept photocurrent tests, the F16CuPc–NTZ12 MHJ produces much higher current under radiation than in the dark due to its well-organized donor–acceptor interface formed by annealing, whereas the current of the unannealed samples shows almost no respo...