Inverted organic photovoltaic cells with high open-circuit voltage

We demonstrate high-efficiency small-molecule photovoltaic cells based on subphthalocyanine (SubPc)/C-60 planar heterojunctions with an inverted layer sequence compared with conventional organic cells. The top-illuminated inverted device achieves a power conversion efficiency of 2.4 +/- 0.2%, or approximately 75% that of a conventional planar SubPc/C-60 solar cell on indium tin oxide-coated glass (with a power efficiency of 3.3 +/- 0.1%). The open-circuit voltage of the inverted devices, optimized by tailoring the work function of the layers adjacent to the donor and acceptor, is comparable to the conventional cell. This work suggests that the inverted devices are promising for use on opaque and/or flexible surfaces. (C) 2010 Elsevier B. V. All rights reserved.