Simultaneous heterojunction organic solar cells with broad spectral sensitivity

We demonstrate organic solar cells incorporating two simultaneously active donor-acceptor heterojunctions contained within a single film with sensitivity extending across the visible solar spectrum into the near infrared (NIR). The NIR absorbing material, tin(II)-phthalocyanine (SnPc), is grown into nanocrystalline islands using organic vapor phase deposition. Using an optimized copper phthalocyanine (CuPc)/SnPc/C-60 nanocrystalline network, we obtain a power conversion efficiency of (2.9 +/- 0.2)% under 100 mW/cm(2), AM1.5G illumination. We find that the open circuit voltage of the simultaneous heterojunction is determined by the lowest voltage of the separate donor-acceptor constituent junctions. (c) 2008 American Institute of Physics.