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 large-area 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 <;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 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.