Improvement in stability of bilayer organic solar cells using an ultra-thin Au layer

In order to improve the stability of organic solar cells based on CuPc/C60 planar heterojunction, an ultra-thin layer of Au (∼2 nm) is inserted between CuPc and PEDOT:PSS. Although, short circuit current density (Jsc) and open circuit voltage (Voc) of the device containing Au layer are less than those of the Au-free one, it has comparable power conversion efficiency (ηp) owing to its higher fill factor (FF). In addition, this ultra-thin Au layer enhances the stability of the device significantly. After a month under ambient condition, the device with “indium thin oxide (ITO)/PEDOT:PSS/Au” anode reaches 67% of its initial ηp value, while the ηp of the cell with “ITO/PEDOT:PSS” anode drops to less than half of its initial value. The improvement in stability is ascribed to the more durable Au/CuPc interface in contrast to the PEDOT:PSS/CuPc interface.

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► We investigate stability of OPV devices based on CuPc/C60.
► An Au layer is inserted between PEDOT/PSS and CuPc.
► The devices consisting of an ultra-thin Au layer shows improved stability.
► The power conversion efficiency of the cell is not decreased by Au layer.