Photovoltaic effects of diodes containing lanthanide complexes

We present a systematic study of organic photovoltaic (PV) diodes containing a series of lanthanide (Ln) complexes, tris(dibenzoylmethanato) (monobathophenanthroline) (Ln)(III) [Ln(DBM)3 bath] used as an electron acceptor. For making a convenient comparison among all diodes, they were fabricated by adopting the same structure, ITO/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-l,l′-diphenyl-4,4′-diamine (TPD) (30 nm)/Ln(DBM)3 bath (60 nm)/Mg:Ag (200 nm), which was not optimized. Although these diodes under bias voltage almost show an exciplex emission relating to PV effects, they indicate distinct performances due to their different 4f electrons and fn configurations. Especially, the PV effects of the diodes containing La3+ (4f0), Y3+ (4f0), Gd3+ (4f7), and Lu3+ (4f14)-complexes having the relative stable electron configurations in the 4f orbital are best under illumination with 365 nm UV light. And the diodes containing Pr3+-, Yb3+-, and Sm3+-complexes have better PV effects, the other diodes containing Ln(DBM)3 bath (Ln: Nd, Eu, Tb, Dy, Ho, Er and Tm) only show poor PV effects.