Improving an organic photodiode by incorporating a tunnel barrier between the donor and acceptor layers

We demonstrate increased photocurrent quantum efficiency in a model donor/acceptor (tetracene/C-60) photodiode by incorporating an insulating tunnel barrier between the tetracene and C-60 layers. Photodiode efficiency results from the interplay of a number of processes which add to or subtract from the overall device efficiency. The positive rates are those of exciton dissociation and charge separation, the negative rates include exciton and charge transfer complex recombination. We show that by introducing a thin insulating layer between the donor and acceptor layers in a photodiode, we can modify the exciton dissociation and charge transfer complex recombination rates and improve device performance. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4734505]