N,N′-diphenylperylene diimide functioning as a sensitizing light absorber based on excitation transfer for organic thin-film solar cells

We demonstrated that N,N′-diphenylperylene tetracarbonic diimide (PTCDI-Ph) could work as an n-type sensitizing layer for the C₆₀ n-type layer owing to interlayer excitation transfer (ET) when the PTCDI-Ph layer was placed between the C₆₀ layer and the aluminum anode coupled with the bathocuproine layer. Well-aligned lowest unoccupied molecular orbitals between C₆₀ and PTCDI-Ph (?4.55 eV for PTCDI-Ph and ?4.5 eV for C₆₀) and a larger bandgap for PTCDI-Ph than C₆₀ (2.04 eV for PTCDI-Ph and 2.0 eV for C₆₀) enabled this interlayer ET-based sensitization. Further, the optical interference effect could be also involved in the sensitization. It was also demonstrated that the combination of both n-type materials C₆₀ and PTCDI-Ph could successfully reduce the amount of the expensive C₆₀ used, and a thin C₆₀ layer was indispensable for efficient charge separation. PTCDI-Ph could work as a light-harvesting n-type material incorporating C₆₀-based cells to compensate for C₆₀’s weak optical absorption.