Metal phthalocyanine and fullerene are typical p-type and n-type organic semiconductors and are often used as constituents of model systems of organic photovoltaics (OPVs). The light-electricity conversion efficiency of the OPVs is influenced by many factors, and a composite structure is one of them. In the present study, time-resolved X-ray photoelectron spectroscopy has been utilized to examine the influence of the stacking order of copper phthalocyanine (CuPc) and fullerene (C60) on photoexcited carrier dynamics in layered CuPc-C60thin-film OPVs fabricated on a rutile TiO2(110) substrate. TiO2is a strong n-type semiconductor and is found to serve as an electron acceptor, which collects the excited electrons in both CuPc and C60layers irrespective of their stacking order. However, a clear difference is found in the electron transfer from C60to TiO2in short delay times below 1 ns; an electron transfer is facilitated in CuPc/C60/TiO2stacking, whereas the fast electron transfer is suppressed in C60/CuPc/TiO2stacking. The insertion of the CuPc layer between C60and TiO2is effective to block the C60→ TiO2electron transfer even though the CuPc layer has a monolayer thickness.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films