Highly efficient semitransparent tandem organic solar cells with complementary absorber materials

We present highly efficient, semitransparent small molecule organic solar cells. The devices employ an indium tin oxide-free top contact, consisting of thin metal films. An additional organic layer is used to enhance light outcoupling. The solar cell incorporates two stacked subcells, each containing a donor: acceptor bulk heterojunction. The two subcells have complementary absorbers, with separate blue (C-60), red (fluorinated zinc phthalocyanine), and green (dicyanovinyl oligothiophene derivative) absorbing molecules. A power conversion efficiency of 4.9 +/- 0.2% is obtained for the device having an average transmission of 24% in the visible range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3610551]