Near infrared sensitive organic photodiode utilizing exciplex absorption in NdPc2/C60 heterojunction

Organic photodiodes (OPDs) have been the subject of extensive research due to their inherent advantages of largearea detection, wide range of material selection and low-cost fabrication. Near infrared (NIR) OPDs were realized mainly by using narrow energy-gap materials and doping organic NIR dyes into the active layer. Here we report on realization of NIR OPDs by exploiting the exciplex absorption in heterojunction consisting of neodymium phthalocyanine (NdPc2) and C60. For NIR OPDs based on NdPc2/C60 planar heterojunction with C60 thickness of 50 nm, the optimal NdPc2-layer thickness for specific detectivity is 30 nm, while that for photoresponsivity is smaller than 10 nm. A maximal specific detectivity of ~4.46×109 Jones was obtained at the optimized NdPc2 layer thickness of 30 nm. At NdPc2 layer thickness of 10 nm, a maximal photoresponsivity of 60 mA/W and a maximal external quantum efficiency (EQE) of 17% were obtained. The results presented here demonstrate that utilizing exciplex absorption in heterojunction based on NdPc2 and C60 is a prospective route for realizing NIR OPDs.