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

► N,N′-diphenylperylene diimide (PTCDI-Ph) sensitized weakly optical absorbing C60. ► Interlayer excitation transfer from PTCDI-Ph to C60 caused the sensitization. ► Optical interference effect also caused it. ► A two-layered stack of PTCDI-Ph and C60 could reduce the amount of expensive C60. ► This is because only a thin C60 layer was required for charge separation.